KEY TERMS AND CONCEPTS

Fitness
Fitness is a general term used to describe the ability to perform physical work. Performing physical work requires cardiorespiratory functioning, muscular strength and endurance, and musculoskeletal flexibility. Optimum body composition is also included when describing fitness.

To become physically fit, individuals must participate regularly in some form of physical activity that uses large muscle groups and challenges the cardiorespiratory system. Individuals of all ages can improve their general fitness status by participating in activities that include walking, biking, running, swimming, stair climbing, cross-country skiing, and/or training with weights.

Fitness levels can be described on a continuum from poor to superior based on energy expenditure during about of physical work. These ratings are often based on direct or indirect measurement of the body’s maximum oxygen consumption ( O2 max). Oxygen consumption is influenced by age, gender, heredity, inactivity, and disease.

Maximum Oxygen Consumption
Maximum oxygen consumption is a measure of the body’s capacity to use oxygen. It is usually measured when performing an exercise that uses many large muscle groups such as swimming, walking, and running. It is the maximum amount of oxygen consumed per minute when the individual has reached maximum effort. It is usually expressed relative to body weight, as milliliters of oxygen per kilogram of body weight per minute (mL/kg per minute). It is dependent on the transport of oxygen, the oxygen binding capacity of the blood, cardiac function, oxygen extraction capabilities, and muscular oxidative potential.

Endurance
Endurance (a measure of fitness) is the ability to work for prolonged periods of time and the ability to resist fatigue. It includes muscular endurance and cardiovascular endurance. Muscular endurance refers to the ability of an isolated muscle group to perform repeated contractions over a period of time, whereas cardiovascular endurance refers to the ability to perform large muscle dynamic exercise, such as walking, swimming, and/or biking for long periods of time.

Aerobic Exercise Training (Conditioning)
Aerobic exercise training, or conditioning, is augmentation of the energy utilization of the muscle by means of an exercise program. The improvement of the muscle’s ability to use energy is a direct result of increased levels of oxidative enzymes in the muscles, increased mitochondrial density and size, and an increased muscle fiber capillary supply.
• Training is dependent on exercise of sufficient intensity, duration, and frequency.
• Training produces cardiovascular and/or muscular adaptation and is reflected in an individual’s endurance.
• Training for a particular sport or event is dependent on the specificity principle; that is, the individual improves in the exercise task used for training and may not improve in other tasks. For example, swimming may enhance one’s performance in swimming events but may not improve one’s performance in treadmill running.

Adaptation
The cardiovascular system and the muscles used adapt to the training stimulus over time. Significant changes can be measured in as little as 10 to 12 weeks.

Adaptation results in increased efficiency of the cardiovascular system and the active muscles. Adaptation represents a variety of neurological, physical, and biochemical changes in the cardiovascular and muscular systems. Performance improves in that the same amount of work can be performed after training but at a lower physiological cost.

Adaptation is dependent on the ability of the organism to change and the training stimulus threshold (the stimulus that elicits a training response). The person with a low level of fitness has more potential to improve than the one who has a high level of fitness.

Training stimulus thresholds are variable. The higher the initial level of fitness, the greater the intensity of exercise needed to elicit a significant change.

Myocardial Oxygen Consumption
Myocardial oxygen consumption is a measure of the oxygen consumed by the myocardial muscle. The need or demand for oxygen is determined by the heart rate (HR), systemic blood pressure, myocardial contractility, and afterload. Afterload is determined by the left ventricular wall tension and central aortic pressure. It is the ventricular force required to open the aortic valve at the beginning of systole. Left ventricular wall tension is primarily determined by ventricular size and wall thickness.

The ability to supply the myocardium with oxygen is dependent on the arterial oxygen content (blood substrate), hemoglobin oxygen dissociation, and coronary blood flow, which is determined by aortic diastolic pressure, duration of diastole, coronary artery resistance, and collateral circulation. In a healthy individual, a balance between myocardial oxygen supply and demand is maintained during maximum exercise. When the demand for oxygen is greater than the supply, myocardial ischemia results.

Deconditioning
Deconditioning occurs with prolonged bed rest, and its effects are frequently seen in the patient who has had an extended, acute illness or long-term chronic condition. Decreases in maximum oxygen consumption, cardiac output (stroke volume), and muscular strength occur rapidly. These effects are also seen, although possibly to a lesser degree, in the individual who has spent a period of time on bed rest without any accompanying disease process and in the individual who is sedentary because of lifestyle and increasing age.

Energy Systems, Energy Expenditure, and Efficiency

Energy Systems
Energy systems are metabolic systems involving a series of biochemical reactions resulting in the formation of adenosine triphosphate (ATP), carbon dioxide, and water. The cell uses the energy produced from the conversion of ATP to adenosine diphosphate (ADP) and phosphate (P) to perform metabolic activities. Muscle cells use this energy for actin-myosin cross-bridge formation when contracting. There are three major energy systems. The intensity and duration of activity determine when and to what extent each metabolic system contributes.

Deconditioning Effects Associated With Bed Rest
Muscle mass
Strength
Cardiovascular function
Total blood volume
Plasma volume
Heart volume
Orthostatic tolerance
Exercise tolerance
Bone mineral density

Phosphagen, or ATP-PC, System
The ATP-PC system (adenosine triphosphate-phosphocreatine) has the following characteristics.
• Phosphocreatine and ATP are stored in the muscle cell.
• Phosphocreatine is the chemical fuel source.
• No oxygen is required (anaerobic).
• When muscle is rested, the supply of ATP-PC is replenished.
• The maximum capacity of the system is small (0.7 mol ATP).
• The maximum power of the system is great (3.7 mol ATP/min).
• The system provides energy for short, quick bursts of activity.
• It is the major source of energy during the first 30 seconds of intense exercise.

Anaerobic Glycolytic System
The anaerobic glycolytic system has the following characteristics.
• Glycogen (glucose) is the fuel source (glycolysis).
• No oxygen is required (anaerobic).
• ATP is resynthesized in the muscle cell.
• Lactic acid is produced (by-product of anaerobic glycolysis).
• The maximum capacity of the system is intermediate (1.2 mol ATP).
• The maximum power of the system is intermediate (1.6 mol ATP/min).
• The systems provide energy for activity of moderate intensity and short duration.
• It is the major source of energy from the 30th to 90th second of exercise.

Aerobic System
The aerobic system has the following characteristics.
• Glycogen, fats, and proteins are fuel sources and are utilized relative to their availability and the intensity of the exercise.
• Oxygen is required (aerobic).
• ATP is resynthesized in the mitochondria of the muscle cell. The ability to metabolize oxygen and other substrates is related to the number and concentration of the mitochondria and cells.
• The maximum capacity of the system is great (90.0 mol ATP).
• The maximum power of the system is small (1.0 mol ATP/min).
• The system predominates over the other energy systems after the second minute of exercise.

Recruitment of Motor Units
Recruitment of motor units is dependent on the rate of work. Fibers are recruited selectively during exercise.
• Slow-twitch fibers (type I) are characterized by a slow contractile response, are rich in myoglobin and mitochondria, have a high oxidative capacity and a low anaerobic capacity, and are recruited for activities demanding endurance. These fibers are supplied by small neurons with a low threshold of activation and are used preferentially in low-intensity exercise.
• Fast-twitch fibers (type IIB) are characterized by a fast contractile response, have a low myoglobin content and few mitochondria, have a high glycolytic capacity, and are recruited for activities requiring power.
• Fast-twitch fibers (type IIA) have characteristics of both type I and type IIB fibers and are recruited for both anaerobic and aerobic activities.

Functional Implications
• Bursts of intense activity (seconds) develop muscle strength and stronger tendons and ligaments. ATP is supplied by the phosphagen system.
• Intense activity (1 to 2 minutes) repeated after 4 minutes of rest or mild exercise enhances anaerobic power. ATP is supplied by the phosphagen and anaerobic glycolytic system.
• Activity with large muscles, which is less than maximum intensity for 3 to 5 minutes repeated after rest or mild exercise of similar duration, may develop aerobic power and endurance capabilities. ATP is supplied by the phosphagen, anaerobic glycolytic, and aerobic systems.
• Activity of submaximum intensity lasting 20 to 30 minutes or more taxes a high percentage of the aerobic system and develops endurance.

Energy Expenditure
Energy is expended by individuals engaging in physical activity and is often expressed in kilocalories. Activities can be categorized as light, moderate or heavy by determining the energy cost. The energy cost of any activity is affected by mechanical efficiency and body mass. Factors that affect both walking and running are terrain, stride length, and air resistance.

Quantification of Energy Expenditure
Energy expended is computed from the amount of oxygen consumed. Units used to quantify energy expenditure are kilocalories and METs.
• A kilocalorie is a measure expressing the energy value of food. It is the amount of heat necessary to raise 1 kilogram (kg) of water 1°C. A kilocalorie (kcal) can be expressed in oxygen equivalents. Five kilocalories equal approximately 1 liter of oxygen consumed (5 kcal = 1 liter O2).
• A MET is defined as the oxygen consumed (milliliters) per kilogram of body weight per minute (mL/kg). It is equal to approximately 3.5 mL/kg per minute.

Classification of Activities
Activities are classified as light, moderate, or heavy according to the energy expended or the oxygen consumed while accomplishing them.
• Light work for the average male (65 kg) requires 2.0 to 4.9 kcal/min, or 6.1 to 15.2 mL O2/kg per minute, or 1.6 to 3.9 METs. Strolling 1.6 km/hr, or 1.0 mph, is considered light work.
• Heavy work for the average male (65 kg) requires 7.5 to 9.9 kcal/min, or 23.0 to 30.6 mL O2/kg per minute, or 6.0 to 7.9 METs. Jogging 8.0 km/hr, or 5.0 mph, is considered heavy work.
• Jogging 8.0 km/hr, or 5.0 mph, requires 25 to 28 mL O2/kg per minute and is considered heavy work. The energy expended is equivalent to 8 to 10 kcal/min, or 7 to 8 METs.
• The energy expenditure necessary for most industrial jobs requires more than three times the energy expenditure at rest.
• Energy expenditure of certain physical activities can vary, depending on factors such as skill, pace, and fitness level.

Efficiency
Efficiency is usually expressed as a percentage.

Work output equals force times distance (W = F × D). It can be expressed in power units or work per unit of time (P = w/t). On a treadmill, work equals the weight of the subject times the vertical distance the subject is raised walking up the incline of the treadmill. On a bicycle ergometer, work equals the distance (which is the circumference of the flywheel times the number of revolutions) times the bicycle resistance.

Work input equals energy expenditure and is expressed as the net oxygen consumption per unit of time. With aerobic exercise, the resting volume of oxygen used per unit of time (VO2 value) is subtracted from the oxygen consumed during 1 minute of the steady-state period.
• Steady state is reached within 3 to 4 minutes after exercise has started if the load or resistance is kept constant.
• In the steady-state period, VO2 remains at a constant (steady) value.

Efficiency Expressed as a Percentage

Total net oxygen cost is multiplied by the total time in minutes the exercise is performed. The higher the net oxygen cost, the lower the efficiency in performing the activity. Efficiency of large muscle activities is usually 20% to 25%.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

There is a question of whether similar colors of bands or tubing from different manufacturers may or may not provide similar levels of tension under the same conditions. In a study comparing similar colors and lengths of Thera-Band and Cando tubing (Cando Fabrication Enterprises, White Plains, NY), investigators measured (by means of a strain gauge) the forces generated under similar conditions. They found no appreciable differences between the two products except for the thinnest (yellow) and thickest (silver/gray) grades. In those two grades the Cando tubing produced approximately 30% to 35% higher levels of force than the Thera-Band product. Despite these small differences, it is prudent to use the same product with the same patient.
Selecting the appropriate length. Elastic bands or tubing come in large rolls and can be cut in varying lengths depending on the specific exercise to be performed and the height of a patient or the length of the extremities. The length of the elastic material should be sufficient to attach it securely at both ends. It should be taut but not stretched (resting length) at the beginning position of an exercise.

Remember, the percentage of elongation of the material affects the tension produced. Accordingly, it is essential that the same length of elastic resistance is used each time a particular exercise is performed. Otherwise, the imposed load may be too little or too much from one exercise session to the next even though the same grade (thickness) of elastic is used.

Securing bands or tubing. One end is often tied or attached to a fixed object (doorknob, table leg, or D-ring) or secured by having the patient stand on one end of the material. The other end is grasped or fastened to a nylon loop, which is then placed around a limb segment. The material can also be secured to a harness on a patient’s trunk for resisted walking activities. The band or tubing can also be held in both hands or looped under both feet for bilateral exercise.
Setting up an exercise. With elastic resistance the muscle receives the maximum resistive force when the material is on a stretch and angled 90° to the lever arm (moving bone). The therapist should determine the limb position at which maximum resistance is desired and anchor the elastic material so it is at a right angle at that portion of the range. When the material is at an acute angle to the moving bone, there is less resistance but greater joint compressive force.
It is important to consistently set up the exercise in the same manner from one exercise session to the next. Each time a patient performs a specific exercise, in addition to using the same length of elastic material the patient should assume the same position. A resource by Page and Ellenbecker221 described setups for numerous exercises using elastic resistance.

Progressing exercises. Exercises can be progressed by increasing the number of repetitions of an exercise with the same grade of resistance or by using the next higher grade of elastic band or tubing.

Advantages and Disadvantages of Exercise with Elastic Resistance
Advantages
• Elastic resistance products are portable and relatively inexpensive, making them an ideal choice for home exercise programs.
• Because elastic resistance is not significantly gravity-dependent, elastic bands and tubing are extremely versatile, allowing exercises to be performed in many combinations of movement patterns in the extremities and trunk and in many positions.
• It is safe to exercise at moderate to fast velocities with elastic resistance because the patient does not have to overcome the inertia of a rapidly moving weight. As such, it is appropriate for plyometric training.
Disadvantages
• One of the most significant drawbacks to the use of elastic resistance is the need to refer to a table of figures for quantitative information about the level of resistance for each color-coded grade of material. This makes it difficult to know which grade to select initially and to what extent changing the grade of the band or tubing changes the level of resistance.
• As with free weights, there is no source of stabilization or control of extraneous movements when an elastic band or tubing is used for resistance. The patient must use muscular stabilization to ensure that the correct movement pattern occurs.
• Although the effects of material fatigue are small with typical clinical use (up to 300% deformation in most exercises), elastic bands and tubing should be replaced on a routine basis to ensure patient safety. If many individuals use the same precut lengths of bands or tubing, it may be difficult to determine how much use has occurred.
• Some elastic products contain latex, thus eliminating use by individuals with an allergy to latex. However, there are latex-free products on the market at a relatively comparable cost.

Equipment for Closed-Chain Training
Many closed-chain exercises are performed in weight-bearing postures to develop strength, endurance, and stability across multiple joints. Typically, these exercises use partial or full body weight as the source of resistance. Examples in the lower extremities include squats, lunges, and step-ups or step-downs; and in the upper extremities they include push-ups or press-ups in various positions and pull-ups or chin-ups. These exercises can be progressed by simply adding resistance with handheld weights, a weighted belt or vest, or elastic resistance. Progressing from bilateral to unilateral weight bearing (when feasible) also increases the exercise load.

The following equipment is designed specifically for closed-chain training and has features to improve muscle performance across multiple joints.

Body Weight Resistance—Multipurpose Exercise Systems
The Total Gym® system, for example, uses a glideboard, which can be set at 10 incline angles, that enables a patient to perform bilateral or unilateral closed-chain strengthening and endurance exercises in positions that range from partially reclining to standing. The level of resistance on the Total Gym apparatus is increased or decreased by adjusting the angle of the glideboard on the incline.

Performance of bilateral and, later, unilateral squatting exercises in a semireclining position allows the patient to begin closed-chain training in a partially unloaded (partial weight-bearing) position early in the rehabilitation program. Later, the patient can progress to forward lunges (where the foot slides forward on the glideboard) while in a standing position.

NOTE: The Total Gym® system can also be set up for trunk exercises and open-chain exercises for the upper or lower extremities.

Balance Boards
A balance board (wobble board) is used for proprioceptive training in the upper or lower extremities. One example is the BAPS (Biomechanical Ankle Platform) system. This system can be used in the standing position, the seated position (with the foot placed on the board) for ankle exercises, or in the quadriped position for upper extremity activities. Progressively increasing the size of the half spheres under the board or placing weights on the board makes the balance activity more challenging.

Slide Boards
The ProFitter® consists of a moving platform that slides side to side across an elliptical surface against adjustable resistance. Although it is most often used with the patient standing for lower extremity rehabilitation, it can also provide upper extremity closed-chain resisted movements and trunk stability. Medial-lateral or anterior-posterior movements are possible.

Mini-Trampolines (Rebounders)
Mini-trampolines enable the patient to begin gentle, bilateral or unilateral bouncing activities on a resilient surface to decrease the impact on joints. A patient can jog, jump, or hop in place. “Mini-tramps” that have a waist-height bar (attached to the frame) to hold onto provide additional safety.

Reciprocal Exercise Equipment
Similar to other types of equipment that can be used for closed-chain training, reciprocal exercise devices strengthen multiple muscle groups across multiple joints. They also are appropriate for low-intensity, high-repetition resistance training to increase muscular endurance and reciprocal coordination of the upper or lower extremities and improve cardipulmonary fitness. They are often used for warm-up or cool-down exercises prior to and after more intense resistance training. Resistance is imparted by an adjustable friction device or by hydraulic or pneumatic resistance.

Stationary Exercise Cycles
The stationary exercise cycle (upright or recumbent) is used to increase lower extremity strength and endurance. An upright cycle requires greater trunk control and balance than a recumbent cycle. A few exercise cycles provide resistance to the upper extremities as well. Resistance can be graded to challenge the patient progressively. Distance, speed, or duration of exercise can also be monitored.

The exercise cycle provides resistance to muscles during repetitive, nonimpact, and reciprocal movements of the extremities. Passive devices resist only concentric muscle activity as the patient performs pushing or pulling movements. Motor-driven exercise cycles can be adjusted to provide eccentric as well as concentric resistance. The placement of the seat can also be adjusted to alter the arc of motion that occurs in the lower extremities.

Portable Resistive Reciprocal Exercise Units
A number of portable resistive exercisers are effective alternatives to an exercise cycle for repetitive, reciprocal exercise. One such product, the Chattanooga Group Exerciser®, can be used for lower extremity exercise by placing the unit on the floor in front of a chair or wheelchair. This is particularly appropriate for a patient who is unable to get on and off an exercise cycle. In addition, it can be placed on a table for upper extremity exercise. Resistance can be adjusted to meet the abilities of individual patients.

Stair-Stepping Machines
The StairMaster® and the Climb Max 2000® are examples of a stepping machines that allow the patient to perform reciprocal pushing movements against adjustable resistance to make the weight-bearing activity more difficult. Stepping machines provide nonimpact, closed-chain strengthening as an alternative to walking or jogging on a treadmill. A patient can also kneel next to the unit and place both hands on the foot plates to use this equipment for upper extremity closed-chain exercises.

Elliptical Trainers and Cross-Country Ski Machines
Elliptical trainers and cross-country ski machines also provide nonimpact, reciprocal resistance to the lower extremities in an upright, weight-bearing position. Variable incline adjustments of these units further supplement resistance options. Both types of equipment also incorporate sources of reciprocal resistance to the upper extremities into their designs.

Upper Extremity Ergometers
Upper body ergometers (UBEs) provide resistance exclusively for the upper extremities. Typically, the patient is seated, but the UBE can also be used with the patient in a standing position to lessen the extent of elevation of the arms necessary with each revolution. This is particularly helpful for patients with impingement syndromes of the shoulder.

Equipment for Dynamic Stabilization Training

Swiss Balls (Stability Balls)
Heavy-duty vinyl balls, usually 20 to 30 inches in diameter, are used for a variety of trunk and extremity stabilization exercises. A patient can also use elastic resistance or free weights while on the ball to increase the difficulty of exercises.

BodyBlade®
The BodyBlade® is a dynamic, reactive form of resistance equipment that uses the principle of inertia as the source of resistance to produce dynamic stability. While a patient drives the blade, rapidly, alternating contractions of agonist and antagonist muscle groups occur in an attempt to control the instability in three planes of motion dictated by movements of the blade. The greater the amplitude or flex of the blade, the greater the resistance. This provides progressive resistance that the patient controls.

Initially, the oscillating blade is maintained in various positions in space, particularly those positions in which dynamic stability is required for functional activities. The patient can progress the difficulty of the stabilization exercises by moving the upper extremity through various planes of motion (from sagittal to frontal and ultimately to transverse) as the blade oscillates. The goal is to develop proximal stability (a stable core) as a foundation of controlled mobility.

Isokinetic Testing and Training Equipment
Isokinetic dynamometers (rate-limiting devices that control the velocity of motion) provide accommodating resistance during dynamic exercises of the extremities or trunk. The equipment supplies resistance proportional to the force generated by the person using the machine. The preset rate (degrees per second) cannot be exceeded no matter how vigorously the person pushes against the force arm. Therefore, the muscle contracts to its fullest capacity at all points in the ROM.

Features of Isokinetic Dynamometers
New product lines of isokinetic equipment and improvements in existing equipment have been developed over the years. The Biodex isokinetic dynamometer is an example of a unit currently on the market. The specifications of the various manufacturers’ dynamometers differ somewhat. Features include computerized testing capabilities; passive and active modes that permit open-chain, concentric and eccentric testing and training; and velocity settings from 0° per second up to 500° per second for the concentric mode and up to 120° to 250° per second for the eccentric mode. Isokinetic units can be used for continuous passive motion. Computer programming allows limb movement within a specified range. Single-joint, uniplanar movements are most common, but some multiplanar movement patterns are possible. The Biodex dynamometer has attachments for multijoint, closed-chain exercises. Reciprocal training of agonist and antagonist and concentric/eccentric training of the same muscle group are both possible.

Advantages and Disadvantages of Isokinetic Equipment
Advantages
• Isokinetic equipment can provide maximum resistance at all points in the ROM as a muscle contracts.
• Both high- and low-velocity training can be done safely and effectively.
• The equipment accommodates for a painful arc of motion.
• As a patient fatigues, exercise can still continue.
• Isolated strengthening of muscle groups is possible to correct strength deficits in specific muscle groups.
• External stabilization keeps the patient and moving segment well aligned.
• Concentric and eccentric contractions of the same muscle group can be performed repeatedly, or reciprocal exercise of opposite muscle groups can be performed, allowing one muscle group to rest while its antagonist contracts; the latter method minimizes muscle ischemia.
• Computer-based visual or auditory cues provide feedback to the patient so submaximal to maximal work can be carried out more consistently.

Disadvantages
• The equipment is large and expensive.
• Setup time and assistance from personnel are necessary if a patient is to exercise multiple muscle groups.
• The equipment cannot be incorporated into a home exercise program.
• Most units allow only open-chain (non-weight-bearing) movement patterns, which do not simulate most lower extremity functions and some upper extremity functions.
• Although functional movements typically occur in combined patterns and at many different velocities, most exercises are performed in a single plane and at a constant velocity.
• Although the range of concentric training velocities (up to 500°/sec) is comparable to some lower extremity limb speeds during functional activities, even the upper limits of this range cannot begin to approximate the rapid limb speeds that are necessary during many sports-related motions, such as throwing. In addition, the eccentric velocities available, at best, only begin to approach medium-range speeds, far slower than the velocity of movement associated with quick changes of direction and deceleration. Both of these limitations in the range of training velocities compromise carryover to functional goals.

Equipment for Isometric Training
To complete the total picture of the importance of equipment for effective resistance training, isometric resistance exercises must also be addressed. One of the advantages of isometric training is that it is possible to perform a variety of exercises without equipment. For example, multiple-angle isometrics can be carried out by simply having the patient push against an immovable object, such as a door frame, a heavy table, a sofa, or a wall. Of course, manual resistance is also an effective means of strengthening muscles isometrically, particularly early in a rehabilitation program.

Many pieces of equipment designed for dynamic exercise can be adapted for isometric exercise. A weight-pulley system that provides resistance greater than the force-generating capacity of a muscle results in a static muscle contraction. Most isokinetic devices can be set up with the speed set at 0°/sec at multiple joint angles for isometric resistance at multiple points in the ROM. If elastic resistance or a pulley system is applied to the sound lower extremity, as the patient stands and bears full weight on the involved lower extremity, the muscles of the involved extremity must contract isometrically to hold the body in a stable, upright position as the sound extremity moves against the resistance.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

Although most equipment is load resisting (augments the resistance of gravity), a few pieces of equipment can be adapted to be load assisting (eliminates or diminishes the resistance of gravity) to improve the strength of weak muscles. Equipment can be used for static or dynamic, concentric or eccentric, and open-chain or closed-chain exercises to improve muscular strength, power, or endurance, neuromuscular stability or control, as well as cardiopulmonary fitness.

In the final analysis, the choice of equipment depends primarily on the individual needs, abilities, and goals of the person using the equipment. Other factors that influence the choice of equipment are the availability; the cost of purchase or maintenance by a facility or a patient; the ease of use (application or setup) of the equipment; the versatility of the equipment; and the space requirements of the equipment. Once the appropriate equipment has been selected, its safe and effective use is the highest priority. General principles for use of equipment are listed below.

General Principles for the Selection and Use of Equipment
• Base the selection of equipment on a comprehensive examination and evaluation of the patient.
• Determine when in the exercise program the use of equipment should be introduced and when it should be altered or discontinued.
• Determine if the equipment could or should be set up and used independently by a patient.
• Teach appropriate exercise form before adding resistance with the equipment.
• Teach and supervise the application and use of the equipment before allowing a patient to use the equipment independently.
• Adhere to all safety precautions when applying and using the equipment.
• Be sure all attachments, cuffs, collars, and straps are securely fastened and that the equipment is appropriately adjusted to the individual patient prior to the exercise.
• Apply padding for comfort, if necessary, especially over bony prominences.
• Stabilize or support appropriate structures to prevent unwanted movement and to prevent undue stress on body parts.
• If exercise machines are used independently, be certain that set-up and safety instructions are clearly illustrated and affixed directly to the equipment.
• If compatible with the selected equipment, use range-limiting attachments if ROM must be restricted to protect healing tissues or unstable structures.
• If the patient is using the equipment in a home program, give explicit instructions on how, when, and to what extent to change or adapt the equipment to provide a progressive overload.
• When making a transition from use of one type of resistance equipment to another, be certain that the newly selected equipment and method of set-up initially provides a similar level of torque production to the equipment previously employed to avoid insufficient or excessive loads.
• When the exercise has been completed:
• Disengage the equipment and leave it in proper condition for future use.
• Never leave broken or potentially hazardous equipment for future use.
• Set up a regular routine of maintenance, replacement, or safety checks for all equipment.

Free Weights and Simple Weight-Pulley Systems
Types of Free Weights
Free weights are graduated weights that are handheld or applied to the upper and lower extremities or trunk. They include commercially available dumbbells, barbells, weighted balls, cuff weights, weighted vests, and even sandbags. Free weights can also be fashioned for a home exercise program from readily available materials and objects found around the home.

Simple Weight-Pulley Systems
Free-standing or wall-mounted simple weight-pulley systems with weight-plates are commonly used for resisted upper and lower extremity or trunk exercises. Permanent or interchangeable weights are available. Permanent weights are usually stacked with individual weight plates of 5- to 10-pound increments that can be easily adjusted by changing the placement of a single weight key.

NOTE: The simple weight-pulley systems described here are those that impose a relatively constant (fixed) load. Variable resistance weight machines, some of which incorporate pulleys into their designs, are discussed later in this section.

Characteristics of Free Weights and Simple Weight-Pulley Systems
Free weights and weight-pulley systems are resistance equipment that impose a fixed (constant) load. The weight selected, therefore, maximally challenges the contacting muscle at only one portion of the ROM when a patient is in a particular position. The weight that is lifted or lowered can be no greater than what the muscle can control at the point in the ROM where the load provides the maximum torque. In addition, there is no accommodation for a painful arc.

When using free weights, it is possible to vary the point in the ROM at which the maximum resistance load is experienced by changing the patient’s position with respect to gravity or the direction of the resistance load. For example, shoulder flexion may be resisted with the patient standing or supine and holding a weight in the hand.
• Patient position: standing: Maximum resistance is experienced and maximum torque is produced when the shoulder is at 90° of flexion. Zero torque is produced when the shoulder is at 0° of flexion. Torque again decreases as the patient lifts the weight from 90°to 180° of flexion. In addition, when the weight is at the side (in the 0° position of the shoulder), it causes traction force on the humerus; and when overhead, it causes compression force through the upper extremity.
• Patient position: supine: Maximum resistance is experienced and maximum torque is produced when the shoulder is at 0° of flexion. Zero torque is produced at 90° of shoulder flexion. In this position the entire load creates a compression force. The shoulder flexors are not active between 90° and 180° of shoulder flexion. Instead, the shoulder extensors must contract eccentrically to control the descent of the arm and weight.

The therapist must determine at which portion of the patient’s ROM maximum strength is needed and must choose the optimum position in which the exercise should be performed to gain maximum benefit from the exercise.

Simple weight-pulley systems provide maximum resistance when the angle of the pulley is at right angles to the moving bone. As the angle of the pulley becomes more acute, the load creates more compression through the moving bones and joints and less effective resistance.

Unlike many weight machines, neither free weights nor pulleys provide external stabilization to guide the moving segment or restrict ROM. When a patient lifts or lowers a weight to an overhead position, muscles of the scapula and shoulder abductors, adductors, and rotators must synergistically contract to stabilize the arm and keep it aligned in the correct plane of motion. The need for concurrent contraction of adjacent stabilizing muscle groups can be viewed as an advantage or disadvantage. Because muscular stabilization is necessary to control the plane or pattern of movement, less resistance can be controlled with free weights than with a weight machine during the same movement pattern.

Advantages and Disadvantages of Free Weights and Simple Weight-Pulley Systems
• Exercises can be set up in many positions, such as supine, side-lying, or prone in bed or on a cart, sitting in a chair or on a bench, or standing. Many muscle groups in the extremities and trunk can be strengthened by simply repositioning the patient.
• Free weights and simple weight-pulley systems typically are used for dynamic, non-weight-bearing exercises but also can be set up for isometric exercise and resisted weight-bearing activities.
• Stabilizing muscle groups are recruited; however, because there is no external source of stabilization and movements must be controlled entirely by the patient, it may take more time for the patient to learn correct alignment and movement patterns.
• A variety of movement patterns is possible, incorporating single plane or multiplanar motions. An exercise can be highly specific to one muscle or generalized to several muscle groups. Movement patterns that replicate functional activities can be resisted.
• If a large enough assortment of graduated free weights is available, resistance can be increased by very small increments, as little as 1 pound at a time. The weight plates of pulley systems have larger increments of resistance, usually a minimum of 5 pounds per plate.
• Most exercises with free weights and weight-pulley systems must be performed slowly to minimize acceleration and momentum and prevent uncontrolled, end-range movements that could compromise patient safety. It is thought that the use of exclusively slow movements during strengthening activities has less carryover to many daily living activities than the incorporation of slow- and fast-velocity exercises into a rehabilitation program. However, a weighted ball can be used with catching and throwing exercises as part of plyometric training during the advanced phase of upper extremity rehabilitation. • Free weights with interchangeable disks, such as a barbell, are versatile and can be used for patients with many different levels of strength, but they require patient or personnel time for proper assembly.
• Bilateral lifting exercises with barbell weights often require the assistance of a spotter to ensure patient safety, thus increasing personnel time.

Variable-Resistance Machines
Variable-resistance exercise equipment falls into two broad categories: specially designed weight-cable (weight-pulley) machines and hydraulic and pneumatic units. Both categories of equipment impose a variable load on the contracting muscles consistent with the changing torque-producing capabilities of the muscles throughout the available ROM.

Variable Resistance Weight-Cable Systems
Variable-resistance weight-cable machines use a cam in their design. The cam (an elliptical or kidney-shaped disk) in the weight-cable system is designed to vary the load (torque) applied to the contracting muscle even though the weight selected remains the same. In theory, the cam is configured to replicate the length-tension relationship and resultant torque curve of the contracting muscle with the greatest amount of resistance applied in the mid-range. This system varies the external load imposed on the contracting muscle based on the physical dimensions of the “average” individual. How effectively this design provides truly accommodating resistance throughout the full ROM is debatable.

With each repetition of an exercise, the same muscle group contracts and is resisted concentrically and eccentrically. As with simple weight-pulley systems and free weights, exercises must be performed at relatively slow velocities, thus compromising carryover to many functional activities.

Hydraulic and Pneumatic Variable-Resistance Units
Other variable-resistance machines employ hydraulic or pressurized pneumatic resistance to vary the resistance throughout the ROM. These units allow concentric, reciprocal muscle work to agonist and antagonist muscle groups but no eccentric work. Patients can safely exercise at fast velocities with these units. These units also allow a patient to accommodate for a pain-free arc.

Advantages and Disadvantages of Variable-Resistance Machines
• The obvious advantage of these machines compared to constant load equipment is that the effective resistance is adjusted, at least to some extent, to a muscle’s tension-generating capabilities throughout the ROM. The contracting muscle is loaded maximally at multiple points in the ROM, rather than just one small portion of the range.
• Most pieces of equipment are designed to isolate and exercise a specific muscle group. For example, resisted squats are performed on one machine and hamstring curls on another. Some units, such as a leg press or shoulder press, strengthen multiple muscle groups simultaneously.
• Unlike functional movement, most machines allow only single-plane movements, although some newer units now offer a dual-axis design allowing multiplanar motions that strengthen multiple muscle groups and more closely resemble functional movement patterns.
• The equipment is adjustable to a certain extent to allow individuals of varying heights to perform each exercise in a well aligned position.
• Each unit provides substantial external stabilization to guide or limit movements. This makes it easier for the patient to learn how to perform the exercise correctly and safely and helps the patient maintain appropriate alignment without assistance or supervision.
• One of the main disadvantages of weight machines is the initial expense and ongoing maintenance costs. Multiple machines, usually 8 to 10 or more, must be purchased to target multiple major muscle groups. Multiple machines also require a large amount of space in a facility.

Elastic Resistance Bands and Tubing
The use of elastic resistance products in therapeutic exercise programs has become widespread in rehabilitation and has been shown to be an effective method of providing resistance and improving muscle strength.146 Despite the popularity of these products, not until the past 10 years has quantitative information been reported on the actual or relative resistance supplied by elastic products or the level of muscle activation during use. These studies suggest that the effective use of elastic products for resistance training requires not only the application of biomechanical principles but also an understanding of the physical properties of elastic resistance material.

Types of Elastic Resistance
Elastic resistance products, specifically designed for use during exercise, fall into two broad categories: elastic bands and elastic tubing. Elastic bands and tubing are produced by several manufacturers under different product names, the most familiar of which is Thera-Band® Elastic Resistance Bands and Tubing (Hygenic Corp., Akron, OH). Elastic bands are available in an assortment of grades or thicknesses. Tubing comes in graduated diameters and wall thickness that provide progressive levels of resistance. Color-coding denotes the thickness of the product and grades of resistance.

Properties of Elastic Resistance—Implications for Exercise
A number of studies describing the physical characteristics of elastic resistance have provided quantitative information about its material properties. Knowledge of this information enables a therapist to use elastic resistance more effectively for therapeutic exercise programs.
Effect of elongation of elastic material. Elastic resistance provides a form of variable resistance because the force generated changes as the material is elongated. Specifically, as it is stretched, the amount of resistance (force) produced by an elastic band or tubing increases depending on the relative change in the length of the material (percentage of elongation/deformation) from the start to the end of elongation. There is a relatively predictable and linear relationship between the percentage of elongation and the tensile force of the material.

To determine the percentage of elongation, the stretched length must be compared to the resting length of the elastic material. The resting length of a band or tubing is its length when it is laid out flat and there is no stretch applied. The actual length of the material before it is stretched has no effect on the force imparted. Rather, it is the percentage of elongation that affects the tensile forces.

The formula for calculating the percentage of elongation/deformation is:

Percent of elongation = (stretched length - resting length) ÷ resting length × 100

Using this formula, if a 2-foot length of red tubing, for example, is stretched to 4 feet, the percentage of elongation is 100%. With this in mind, it is understandable why a 1-foot length of the same color tubing stretched to 2 feet (100% elongation) generates the same force as a 2-foot length stretched to 4 feet.

Furthermore, the rate at which elastic material is stretched does not seem to have a significant effect on the amount of resistance encountered. Consequently, when a patient is performing a particular exercise, so long as the percentage of elongation of the tubing is the same from one repetition to the next, the resistance encountered is the same regardless of whether the exercise is performed at slow or fast velocity.

Determination and quantification of resistance. In order to make decisions based on evidence, rather than solely on clinical judgment, about the grade (color) of elastic material to select for a patient’s exercise program, a number of studies have been done to quantify the resistance imparted by elastic bands or tubing. These studies measured and compared the tensile forces generated by various grades of elastic bands or tubing in relation to the percentage of elongation of the material. The forces expected at specific percentages of elongation of each grade of tubing or bands can be calculated by means of linear regression equations. Detailed specifications about the material properties of one brand of elastic resistance products, Thera-Band,® are available at www.thera-bandacademy.com/.

During exercise, the percentage of deformation and resulting resistance (force) from the material is not the only factor that must be considered. The amount of torque (force × distance) imposed by the elastic on the bony lever is also an important consideration. Just because the tension produced by an elastic band or tubing increases as it is stretched, it does not mean that the imposed torque necessarily increases from the beginning to the end of an exercise. In addition to the resistance (force) imposed by the elastic material as it is stretched, the factor of the changing length of the moment arm as the angle of the elastic changes with respect to the moving limb affects the torque imparted by the elastic material. Studies have indicated that bell-shaped torque curves occur, with the peak torque near mid-range during exercises with elastic material. Careful scrutiny of these studies is necessary to determine if the elastic resistance is at a 90° angle to the moving limb at mid-range. As in all forms of dynamic resistance exercise, the length-tension relationship of the contracting muscle also affects its ability to respond to the changing load.

Fatigue characteristics. It has been suggested that elastic resistance products tend to fatigue over time, which causes the material to lose some of its force-generating property. That being said, the extent of material fatigue is dependent on the number of times the elastic band or tubing has been stretched (number of stretch cycles) and the percentage of deformation with each stretch.

Studies have shown that the decrease in tensile force is significant but small, with much of the decrease occurring within the first 20 or 50 stretch cycles. However, in the former study, investigators found that after this small initial decrease in tensile force occurred there was no appreciable decrease in the force-generating potential of the tubing after more than 5000 cycles of stretch. In other words, a patient could perform 10 repetitions each of four different exercises, three times a day on a daily basis for 6 weeks with the same piece of tubing before needing to replace it.

Elastic materials also display a property called viscoelastic creep. If a constant load is placed on elastic material, in time it becomes brittle and eventually ruptures. Environmental conditions, such as heat and humidity, also affect the force-generating potential of elastic bands and tubing.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

PRECAUTIONS: As with other forms of high-intensity resistance training, special precautions must be followed to ensure patient safety. These precautions are listed below.

Isokinetic Regimens
It is well established that isokinetic training improves muscle performance. Its effectiveness in carryover to functional tasks is less clear. Studies support and refute that isokinetic training improves function. Ideally, when isokinetic training is implemented in a rehabilitation program, to have the most positive impact on function it should be performed at velocities that closely match or at least approach the expected velocities of movement of specific functional tasks. Because many functional movements occur at a variety of medium to fast speeds, isokinetic training is typically performed at medium and fast velocities.

Sample Plyometric Sequence for the Upper Extremities
• Warm-up activities
• Trunk exercises holding lightweight ball: rotation, side-bending, wood-chopping
• Upper extremity exercises in anatomical and diagonal planes of motion with light-grade elastic tubing
• Prone push-ups
• Throwing motions with a weighted ball to and from a partner: bilateral chest press; bilateral overhead throw; bilateral side throw
• ER/IR against elastic tubing (90/90 position of shoulder and elbow)
• Diagonal patterns against elastic resistance
• Unilateral throwing motions with weighted ball: baseball throw; side throws
• Additional exercises
• Trunk exercises holding weighted ball: abdominal curl-ups; back extension; sit-up and bilateral throw; long sitting throws
• Clap push-ups
• Prone push-ups from box to floor and back to box

Precautions for Plyometric Training
• If high-stress, shock-absorbing activities are not permissible, do not incorporate plyometric training into a patient’s rehabilitation program.
• If a decision is made to include plyometric activities in a rehabilitation program for children or elderly patients, select only beginning-level stretch-shortening drills against light resistance. Do not include high-impact, heavy-load activities—such as drop jumps or weighted jumps—that could place excessive stress on joints.
• Be sure the patient has adequate flexibility and strength before initiating plyometric exercises.
• Wear shoes that provide support for lower extremity plyometrics.
• Always warm-up prior to plyometric training with a series of active, dynamic trunk and extremity exercises.
• During jumping activities, emphasize learning techniques for a safe landing before progressing to rebounding.
• Progress repetitions of an exercise before increasing the level of resistance used or the height or length of jumps.
• For high-level athletes who progress to high-intensity plyometric drills, increase the rest intervals between sets and decrease the frequency of drills as the intensity of the drills increases.
• Allow adequate time for recovery with 48 to 72 hours between sessions of plyometric activities.
• Stop an exercise if a patient can no longer perform the plyometric activity with good form and landing technique because of fatigue.

Current isokinetic technology makes it possible to approximate training speeds to velocities of movement during some lower extremity functions, such as walking. In the upper extremities this is far less possible. Some functional movements in the upper extremities occur at exceedingly rapid velocities (e.g., more than 1000° per second for overhead throwing), which far exceed the capabilities of isokinetic dynamometers.
It is also widely accepted that isokinetic training is relatively speed-specific, with only limited transfer of training (physiological overflow causing improvements in muscle performance at speeds other than the training speed). Therefore, speed-specific isokinetic training, similar to the velocity of a specific functional task, is advocated.

Velocity Spectrum Rehabilitation
To deal with the problem of limited physiological overflow of training effects from one training velocity to another, a regimen called velocity spectrum rehabilitation (VSR) has been advocated. With this system of training, exercises are performed across a range of velocities.

NOTE: The guidelines for VSR that follow are for concentric isokinetic training. General guidelines for eccentric isokinetics are identified at the conclusion of this section.

Selection of training velocities. Typically, medium (60° or 90° to 180°/sec) and fast (180° to 360°/sec) angular velocities are selected. Although isokinetic units are designed for testing and training at velocities faster than 360° per second, the fastest velocities usually are not used for training. This is because the limb must accelerate to the very fast, preset speed before encountering resistance from the torque arm of the dynamometer. Hence, the contracting muscles are resisted through only a small portion of the ROM.
It has been suggested that the effects of isokinetic training (improvements in muscle strength, power, or endurance) carry over only 15° per second from the training velocity. Therefore, some VSR protocols use 30° per second increments for medium and fast velocity training. Of course, if a patient trains at medium and fast velocities (from 60° or 90° to 360°/sec) in one exercise session, this strategy necessitates nine different training velocities, giving rise to a time-consuming exercise session for one agonist/antagonist combination of muscle groups. A more common protocol is to use as few as three training velocities.

Repetitions, sets, and rest. A typical VSR protocol might have the patient perform one or two sets of 8 to 10 or as many as 20 repetitions of agonist/antagonist muscle groups (reciprocal training) at multiple velocities. For example, at medium velocities (between 90° and 180°/sec) training could occur at 90°, 120°, 150°, and 180° per second. A second series would then be performed at decreasing velocities: 180°, 150°, 120°, and 90° per second. Because many combinations of repetitions, sets, and different training velocities lead to improvement in muscle performance, the therapist has many options when designing a VSR program. A 15- to 20-second rest between sets and a 60-second rest between exercise velocities has been recommended. The recommended frequency for VSR is a maximum of three times per week.

Intensity. Submaximal effort is used for a brief warm-up period on the dynamometer. This is not a replacement for a more general form of upper or lower body warm-up exercises, such as cycling or upper-extremity ergometry. When training to improve endurance, exercises are carried out at a submaximal intensity (effort) but at a maximal intensity to improve strength or power.

During the early stages of isokinetic training, it is useful to begin with submaximal isokinetic exercise at intermediate and slow velocities so the patient gets the “feel” of the isokinetic equipment and at the same time protects the muscle. As the program progresses, maximum effort can be exerted at intermediate speeds. Slow-speed training is eliminated when the patient begins to exert maximum effort. During the advanced stage of rehabilitation, maximum-effort, fast-velocity training is emphasized, so long as exercises are pain-free. Additional aspects to a progression of isokinetic training regimens include short-arc to full-arc exercises (if necessary) and concentric to eccentric movements.

PRECAUTION: Maximum-effort, slow-velocity training is rarely indicated because of the excessive shear forces produced across joint surfaces.

Eccentric Isokinetic Training: Special Considerations
As isokinetic technology evolved over several decades, eccentric isokinetic training became possible, but few guidelines for eccentric isokinetic training and evidence of their efficacy are available. Guidelines developed to date are primarily based on clinical opinion or anecdotal evidence. Key differences in eccentric versus concentric isokinetic guidelines (intensity, repetitions, frequency, rest) are listed below. Several resources describe pathology-specific guidelines for eccentric isokinetic training based on clinical experience.

PRECAUTIONS: Eccentric isokinetic training is appropriate only during the final phase of a rehabilitation program to continue to challenge individual muscle groups when isolated deficits in strength and power persist. Because of the robotic nature of eccentric isokinetic training, medium rather than fast training velocities are considered safer. A sudden, rapid, motor-driven movement of the dynamometer’s torque arm against a limb could injure healing tissue.

Key Differences in Eccentric Versus Concentric Isokinetic Training
Eccentric isokinetic exercise is:
• Introduced only after maximal effort concentric isokinetic exercise can be performed without pain
• Implemented only after functional ROM has been restored
• Performed at slower velocities across a narrower velocity spectrum than concentric isokinetic exercise: usually between 60° and 120° per second for the general population and up to 180° per second for athletes
• Carried out at submaximal levels for a longer time frame to avoid extensive torque production and lessen the risk of DOMS
• Most commonly performed in a continuous concentric-eccentric pattern for a muscle group during training

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

For the past 50 to 60 years practitioners and researchers alike in rehabilitation and fitness settings have taken great interest in resistance exercise and functional training. As a result, many systems of exercise have been developed to improve muscle strength, power, and endurance. All of these systems are based on the overload principle, and most use some form of mechanical resistance to load the muscle. The driving force behind the development of these regimens seems to be to design the “optimal”—that is, the most effective and efficient—method to improve muscular performance and functional abilities.

Resistance Training for Older Adults (≥ 60-65 Years): Guidelines and Special Considerations

• Secure approval to initiate exercise from the participant’s physician.

• Institute close supervision during the early phases of training to ensure safety.

• Monitor vital signs, particularly when the program is progressed.

• Perform at least 5 to 10 minutes of warm-up activities before each session of resistance exercises.

• Begin with low-resistance, low-repetition exercises, especially for eccentric exercises, to minimize loads on joints and to allow time for connective tissue as well as muscle to adapt.

• Emphasize low to moderate levels of resistance (at a level that permits 10-12 repetitions) for 6 to 8 weeks. Progress the program during this time by increasing repetitions. Later, increase resistance by small increments.

• Throughout the program avoid high-resistance exercises to avoid excessive stresses on joints.

• Perform resistance training two to three times weekly, allowing a 48-hour rest interval between sessions.

• Modify exercises for age-related postural changes, such as excessive kyphosis, that can alter the biomechanics of an exercise.

• Avoid flexion-dominant resistance training that could emphasize postural changes.

• When possible, use weight machines that allow the participant to perform exercises in a seated position to avoid loss of balance.

• Reduce the intensity and volume of weight training by 50% after a 1- to 2-week layoff.

Several frequently used regimens of resistance training for the advanced phase of rehabilitation and for conditioning programs have been selected for discussion in this section. They are progressive resistive exercise (PRE), circuit weight training, plyometric training (stretch-shortening drills), and isokinetic training regimens.

Progressive Resistance Exercise

Progressive resistance exercise (PRE) is a system of dynamic resistance training in which a constant external load is applied to the contracting muscle by some mechanical means (usually a free weight or weight machine) and incrementally increased. The repetition maximum (RM) is used as the basis for determining and progressing the resistance.

Delorme and Oxford Regimens

The concept of PRE was introduced almost 60 years ago by DeLorme, who originally used the term heavy resistance training and later load-resisting exercise to describe a new system of strength training. DeLorme proposed and studied the use of three sets of a 10 RM with progressive loading during each set. Other investigators developed a regimen, the Oxford technique, with regressive loading in each set.

The DeLorme technique builds a warm-up period into the protocol, whereas the Oxford technique diminishes the resistance as the muscle fatigues. Both regimens incorporate a rest interval between sets; both incrementally increase the resistance over time; and both have been shown to result in training-induced strength gains over time. In a randomized study comparing the DeLorme and Oxford regimens, no significant difference was found in adaptive strength gains in the quadriceps muscle group in older adults after a 9-week exercise program.

Since the DeLormer and Oxford systems of training were first introduced, numerous variations of PRE protocols have been proposed and studied to determine an optimal intensity of resistance training, optimal number of repetitions and sets, optimal frequency, and optimal progression of loading. In reality, an ideal combination of these variables does not exist. Extensive research has shown that many combinations of exercise load, repetitions and sets, frequency, and rest intervals significantly improve strength. In general, training-induced strength gains occur with two to three sets of 6 to 12 repetitions of a 6 to 12 RM. This gives a therapist wide latitude when designing an effective weight-training program.

DAPRE Regimen

Knowing when and by how much to increase the resistance in a PRE program to overload the muscle progressively is often imprecise and arbitrary. A common guideline is to increase the weight by 5% to 10% when all prescribed repetitions and sets can be completed easily without significant fatigue. The Daily Adjustable Progressive Resistive Exercise (DAPRE) technique is more systematic and takes into account the different rates at which individuals progress during rehabilitation or conditioning programs. The system is based on a 6 RM working weight. The adjusted working weight, which is based on the maximum number of repetitions possible using the working weight in Set #3 of the regimen, determines the working weight for the next exercise session.

NOTE: It should be pointed out that the recommended increases or decrease in the adjusted working weight are based on progressive loading of the quadriceps muscle group.

Circuit Weight Training

Another system of training that employs mechanical resistance is circuit weight training. A pre-established sequence (circuit) of continuous exercisesis performed in succession at individual exercise stations that target a variety of major muscle groups (usually 8 to 12) as an aspect of total body conditioning.

Each resistance exercise is performed at an exercise station for a specified number of repetitions and sets. Typically, repetitions are higher and intensity (resistance) is lower than in other forms of weight training. For example, two to three sets of 8 to 12 repetitions at 90% to 100% 10 RM or 10 to 20 repetitions at 40% to 50% 1 RM are performed, with a minimum amount of rest (15 to 20 seconds) between sets and stations. The program is progressed by increasing the number of sets or repetitions, the resistance, the number of exercise stations, and the number of circuit revolutions.

Exercise order is an important consideration when setting up a weight training circuit. Exercises with free weights or weight machines should alternate among upper extremity, lower extremity, and trunk musculature and between muscle groups involved in pushing or pulling actions. This enables one muscle group to rest and recover from exercise while exercising another group and, therefore, minimizes muscle fatigue. Ideally, larger muscle groups should be exercised before smaller muscle groups. Multijoint exercises that recruit multiple muscle groups should be performed before exercises that recruit an isolated muscle group to minimize the risk of injury from fatigue.

Plyometric Training—Stretch-Shortening Drills

High-intensity, high-velocity exercises emphasize the development of muscular power and coordination. Reactive bursts of force in functional movement patterns are often necessary if a patient is to return to high-demand occupational, recreational, or sport-related activities. Plyometric training is integrated into the advanced phase of rehabilitation as a mechanism to train the neuromuscular system to react quickly in order to prepare for activities that require rapid starting and stopping movements. This form of training is appropriate only for carefully selected patients.

Definitions and Characteristics

Plyometric training, also called stretch-shortening drills or stretch-strengthening drills, employs high-velocity eccentric to concentric muscle loading, reflexive reactions, and functional movement patterns. Plyometric training is defined as a system of high-velocity resistance training characterized by a rapid eccentric contraction during which the muscle elongates, immediately followed by a rapid reversal of movement with a resisted shortening contraction of the same muscle. The rapid eccentric loading phase is the stretch cycle, and the concentric phase is the shortening cycle. The period of time between the stretch and shortening cycles is known as the amortization phase. It is important that the amortization phase is kept very brief by a rapid reversal of movements to capitalize on the increased tension in the muscle.

Body weight or an external form of loading, such as elastic bands or tubing or a weighted ball, are possible sources of resistance.

Plyometric Activities for the Upper and Lower Extremities

Upper Extremities

• Catching and throwing a weighted ball with a partner or against a wall: bilaterally then unilaterally

• Stretch-shortening drills with elastic tubing using anatomical and diagonal motions

• Dribbling a ball on the floor or against a wall

• Drop push-ups: from boxes to floor and back to boxes

• Clap push-ups

Lower Extremities

• Repetitive jumping on the floor: in place; forward/backward; side to side; diagonally to four corners; jump with rotation; zigzag jumping; later, jump on foam

• Vertical jumps and reaches

• Multiple jumps across a floor (bounding)

• Box jumping: initially off and freeze; then off and back on box increasing speed and height

• Side to side jumps (box to floor to box)

• Jumping over objects on the floor

• Hopping activities: in place; across a surface; over objects on the floor

• Depth jumps (advanced): jump from a box, squat to absorb shock, and then jump and reach as high as possible

Neurological and Biomechanical Influences

Plyometric training is thought to utilize the series-elastic properties of soft tissues and the stretch reflex of the neuromuscular unit. The spring-like properties of the series-elastic components of muscle-tendon units create elastic energy during the initial phase (the stretch cycle) as the muscle contracts eccentrically and lengthens while loaded. This energy is briefly stored and then retrieved for use during the concentric contraction (shortening cycle) that follows. The storage and release of this elastic energy augments the force production of the concentric muscle contraction.

Furthermore, the stretch-shortening cycle is thought to stimulate the proprioceptors of muscles, tendons, ligaments, and joints, increase the excitability of the neuromuscular receptors, and improve the reactivity of the neuromuscular system. The term reactive  neuromuscular training has also been used to describe this approach to exercise. More specifically, the loaded, eccentric contraction (stretch cycle) is thought to prepare the contractile elements of the muscle for a concentric contraction (shortening cycle) by stimulation and activation of the monosynaptic stretch reflex. Muscle spindles, the receptors that lie in parallel with muscle fibers, sense the length of a muscle and the velocity of stretch applied to a muscle and transmit this information to the CNS via afferent pathways. Impulses are then sent back to the muscle from the CNS, which reflexively facilitates activation of a shortening contraction of the stretched muscle (the shortening cycle). Therefore, the more rapid the eccentric muscle contraction (the stretch), the more likely it is that the stretch reflex will be activated.

It has been suggested that the ability to use this stored elastic energy and neural facilitation is contingent on the velocity and magnitude of the stretch and the transition time between the stretch and shortening phases (the amortization phase). During the amortization phase the muscle must reverse its action, switching from deceleration to acceleration of the load. A decrease in the amortization phase theoretically increases the force output during the shortening cycle.

Effects of Plyometric Training

The evidence to support the effectiveness of plyometric training to enhance physical performance is somewhat limited, with many resources citing opinion and anecdotal evidence. However, there is evidence indicating that plyometric training is associated with an increase in a muscle’s ability to resist stretch, which may enhance the muscle’s dynamic restraint capabilities. There is also promising evidence to suggest that plyometric training is associated with a decreased incidence of lower extremity injury.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

Mechanical resistance exercise is any form of exercise in which resistance (the exercise load) is applied by means of some type of exercise equipment. Frequently used terms that denote the use of mechanical resistance are resistance training, weight training, and strength training.

Mechanical resistance exercise is an integral component of rehabilitation and conditioning programs for individuals of all ages. However, use of mechanical resistance in an exercise program has some advantages and disadvantages. The positive and negative qualities of specific types of exercise equipment are described in the last section of this chapter.

Advantages

• Establishes a quantitative baseline measurement of muscle performance against which improvement can be judged.

• Most appropriate during intermediate and advanced phases of rehabilitation when muscle strength is 4/5 or greater or when the strength of the patient exceeds the therapist’s strength.

• Heavy exercise loads, far beyond that which can be applied manually by a therapist, can be used to induce a training effect for already strong muscle groups.

• Increases in level of resistance can be incrementally and quantitatively documented.

• Quantitative improvement is an effective source of motivation for the patient.

• Useful for improving dynamic or static muscular strength.

• Adds variety to a resistance training program.

• Practical for improving muscular endurance.

• Some equipment provides variable resistance through the ROM.

• High-velocity resistance training is possible and safe with some forms of mechanical resistance (hydraulic and pneumatic variable resistance machines, isokinetic units, elastic resistance). Potentially better carryover to functional activities than relatively slow-velocity manual resistance exercises.

• Appropriate for independent exercise in a home program after careful patient education and a period of supervision.

Disadvantages

• Not appropriate when muscles are very weak or soft tissues are in the very early stages of healing, with the exception of some equipment that provides assistance, support, or control against gravity.

• Equipment that provides constant external resistance maximally loads the muscle at only one point in the ROM.

• No accommodation for a painful arc (except with hydraulic, pneumatic, or isokinetic equipment).

• Expense for purchase and maintenance of equipment.

• With free weights and weight machines, gradation in resistance is dependent on the manufacturer’s increments of resistance.

Use in Rehabilitation

Mechanical resistance exercise is commonly implemented in rehabilitation programs to eliminate or reduce deficits in muscular strength, power, and endurance caused by an array of pathological conditions and to restore or improve functional abilities.

Use in Conditioning Programs

There is a growing awareness through health promotion and disease prevention campaigns that training with weights or other forms of mechanical resistance is an important component of comprehensive conditioning programs to improve or maintain physical fitness and health throughout most of the life span. As in rehabilitation programs, resistance training complements aerobic training and flexibility exercises in conditioning programs. Guidelines for a balanced resistance training program for the healthy, but untrained adult (less than 50 to 60 years of age) recommended by the American College of Sports Medicine and other resources are summarized below.

Special Considerations for Children and Older Adults

As noted previously, children and older adults often wish to, or may find it necessary to, engage in resistance training in a conditioning program to improve physical fitness, reduce health-related risk factors, or enhance physical performance. Resistance training can be safe and effective if exercise guidelines are modified to meet the unique needs of these two groups.

Summary of Guidelines for Resistance Training in Conditioning Programs for Healthy Adults (< 50-60 years old)

• Prior to resistance training, perform warm-up activities followed by flexibility exercises.

• Perform dynamic exercises that target the major muscle groups of the body (approximately 8-10 muscle groups of the upper and lower extremities and trunk) for total body muscular fitness.

• Balance flexion-dominant (pulling) exercises with extension-dominant (pushing) exercises.

• Move through the full, available, and pain-free ROM.

• Include both concentric (lifting) and eccentric (lowering) muscle actions.

• Use moderate-intensity exercises: at least 8 to 12 repetitions per set.

• Perform 1 to 3 sets of each exercise for 8 to 12 repetitions per set.

• Use slow to moderate speeds of movement.

• Use rhythmic, controlled, nonballistic movements.

• Exercises should not interfere with normal breathing.

• Include rest intervals of 2 to 3 minutes between sets. While resting one muscle group, exercise a different muscle group.

• Frequency: two to three times per week.

• Increase intensity gradually (increments of approximately 5%) to progress the program as strength and muscular endurance improve.

• Whenever possible, train with a partner for feedback and assistance.

• Cool down after completion of exercises.

• After a layoff of more than 1 to 2 weeks, reduce the resistance and volume when reinitiating weight training.

Children and Resistance Training

Until the past decade or two, health professionals have been reluctant to support preadolescent youth participation in resistance training as a part of fitness programs because of concerns about possible adverse stress and injury to the immature musculoskeletal system, in particular, growth-plate injuries and avulsion fractures. Furthermore, a common assumption was that the benefits of resistance training were questionable in children.

There is now a growing body of evidence that demonstrates that children do achieve health-related benefits from resistance training and can safely engage in closely supervised weight-training programs. Use of body weight as a source of resistance and equipment specifically designed to fit a child contributes to program safety. Training-induced strength gains in prepubescent children have been documented, but sports related injury prevention remains of questionable benefit. As with adults, information on the impact of strength training on the enhancement of functional motor skills is limited.

Focus on Evidence

Research has shown that, although some acute and chronic responses of children to exercise are similar to those of adults, other responses are quite different. For example, children dissipate body heat less easily, fatigue more quickly, and may need more time to recover from exercise than young adults. Such differences in response to resistance exercise must be addressed when designing and implementing strength training programs for children.

Accordingly, the American Academy of Pediatrics, the American College of Sports Medicine, and many health professionals support youth involvement in resistance training—but only if a number of special guidelines and precautions are consistently followed.

Although the risk of injury from resistance training is quite low, exercise-induced soft tissue or growth-plate injuries have been noted if guidelines and precautions are not followed. Special guidelines are summarized below. Consistent with adult guidelines, a balanced program of dynamic exercise for major muscle groups includes warm-up and cool-down periods.

Older Adults and Resistance Training

It is well known that muscle performance diminishes with age, and deficits in muscle strength, power, and endurance are associated with a higher incidence of functional limitations and disability. The extent to which decreasing muscle strength is caused by the normal aging process versus a sedentary lifestyle or an increasing incidence of age-related diseases, such as hypertension and osteoarthritis, is not clear.

Resistance Training for Children: Special Guidelines and Special Considerations

• No formal resistance training for children less than 6 to 7 years of age.

• At age 6 to 7, introduce the concept of an exercise session initially using exercises without weights, then with light (only 1- or 2-pound) weights.

• Maintain close and continuous supervision by trained personnel or a parent who has received instruction.

• Focus on proper form, exercise technique, and safety (alignment, stabilization, controlled motion).

• Emphasize low intensity throughout childhood to avoid potential injury to a child’s growing skeletal system and to joints and supportive soft tissues.

• Emphasize a variety of short-duration, play-oriented exercises to prevent boredom, overheating, and muscle fatigue.

• Perform warm-up activities for at least 5 to 10 minutes before initiating resistance exercises.

• Select low exercise loads that allow a minimum of 8 to 12 or 12 to 15 repetitions. Emphasize multijoint, combined movements.

• Perform only one to two sets of each exercise; rest at least 3 minutes between sets of exercises.

• Initially progress resistance training by increasing repetitions, not resistance, or by increasing the total number of exercises. Later, increase weight by no more than 5% at a time.

• Limit the frequency to two sessions per week.

• Use properly fitting equipment that is designed or can be adapted for a child’s size. Many weight machines cannot be adequately adjusted to fit a child’s stature.

A major goal of resistance training in older adults is to maintain or improve their levels of functional independence and reduce the risk of age-related diseases. As with young and middle-aged adults, older adults (less than age 60 to 65) benefit from regular exercise that includes aerobic activity, flexibility exercises, and resistance training. Even in previously sedentary older adults or frail elderly patients, a program of weight training has resulted in training-induced gains in muscle strength – and improvements in a number of parameters of physical function, such as balance, speed of walking, and the ability to rise from a chair. It also has been suggested that strength training in the elderly population may minimize the incidence of falls.

Although many of the guidelines for resistance training that apply to young and middle-aged adults are applicable to healthy older adults, in general, resistance training for older adults should be more closely supervised and initially less rigorous than for younger populations of adults. Accordingly, impaired balance, age-related postural changes, and poor vision that can compromise safety must be addressed if present. Also, because of age-related changes in connective tissue, there is a higher incidence of DOMS and greater muscle fiber damage in older versus young adults after heavy-resistance, high-volume strength training.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

Isokinetic exercise is also called accommodating resistance exercise. Theoretically, if an individual is putting forth a maximum effort during each repetition of exercise, the contracting muscle produces variable but maximum force output, consistent with the muscle’s variable tension-generating capabilities at all portions in the range of movement, not at only one small portion of the range as occurs with DCER training. Although early advocates of isokinetic training suggested it was superior to resistance training with free weights or weight-pulley systems, this claim has not been well supported by evidence. Today, use of isokinetic training is regarded as one of many tools that can be integrated into the later stages of rehabilitation.

Characteristics of Isokinetic Training

A brief overview of the key characteristics of isokinetic exercise are addressed in this section. For more detailed information on isokinetic testing and training, a number of resources are available.

Constant velocity. Fundamental to the concept of isokinetic exercise is that the velocity of muscle shortening or lengthening is preset and controlled by the unit and remains constant throughout the ROM.

Range and selection of training velocities. Isokinetic training affords a wide range of exercise velocities in rehabilitation from very slow to fast velocities. Current dynamometers manipulate the speed of limb movement from 0°/sec up to 500°/sec. As shown in these training velocities are classified as slow, medium, and fast. This range theoretically provides a mechanism by which a patient can prepare for the demands of functional activities that occur at a range of velocities of limb movement.

Selection of training velocities should be as specific as possible to the demands of the anticipated functional tasks. The faster training velocities appear to be similar to or approaching the velocities of limb movements inherent in some functional motor skills such as walking or lifting. For example, the average angular velocity of the lower extremity during walking has been calculated at 230° to 240°/sec. Nevertheless, the velocity of limb movements during many functional activities far exceeds the fastest training velocities available.

The training velocities selected may also be based on the mode of exercise (concentric or eccentric) to be performed.

Reciprocal versus isolated muscle training. Use of reciprocal training of agonist and antagonist muscles emphasizing quick reversals of motion is possible on an isokinetic dynamometer. For example, the training parameter can be set so the patient performs concentric contraction of the quadriceps followed by concentric contraction of the hamstrings. An alternative approach is to target the same muscle in a concentric mode, followed by an eccentric mode, thus strengthening only one muscle group at a time.Both of these approaches have merit.

Specificity of training. Isokinetic training for the most part is speed-specific, with only limited evidence of significant overflow from one training speed to another. Evidence of mode-specificity (concentric vs. eccentric) with isokinetic exercise is less clear. Because isokinetic exercise tends to be speed-specific, patients typically

Compressive forces on joints. During concentric exercise, as force output decreases, the compressive forces across the moving joint are less at faster angular velocities than at slow velocities.

Accommodation to fatigue. Because the resistance encountered is directly proportional to the force applied to the resistance arm of the isokinetic unit, as the contracting muscle fatigues, a patient is still able to perform additional repetitions even though the force output of the muscle temporarily diminishes.

Accommodation to a painful arc. If a patient experiences transient pain at some portion of the arc of motion during isokinetic exercise, this form of training accommodates for the painful arc. The patient simply pushes less vigorously against the resistance arm to move without pain through that portion of the range. If a patient needs to stop a resisted motion because of sudden onset of pain, the resistance is eliminated as soon as the patient stops pushing against the torque arm of the dynamometer.

Training Effects and Carryover to Function

Numerous studies have shown that isokinetic training is effective for improving one or more of the parameters of muscle performance. In contrast, only a limited number of studies have investigated the relationship between isokinetic training and improvement in the performance of functional skills. Two such studies indicated that the use of high-velocity concentric and eccentric isokinetic training was associated with enhanced performance (increased velocity of serving in tennis and throwing a ball).

Several factors inherent in the design of most types of isokinetic equipment may limit the extent to which isokinetic training carries over to improvements in functional performance. Although isokinetic training affords a spectrum of velocities for training, the velocity of limb movement during many daily living and sport-related activities far exceeds the maximum velocity settings available on isokinetic equipment. In addition, limb movements during most functional tasks occur at multiple velocities, not at a constant velocity, depending on the conditions of the task.

Furthermore, isokinetic exercise usually isolates a single muscle or opposite muscle groups, involves movement of a single joint, is uniplanar, and does not involve weight bearing. Although isolation of a single muscle can be beneficial in remediating strength deficits in specific muscle groups, most functional activities require contractions of multiple muscle groups and movement of multiple joints in several planes of motion, some in weight-bearing positions. However, it is important to note that some of these limitations can be addressed by adapting the setup of the equipment to allow multiaxis movements in diagonal planes or multijoint resisted movements with the addition of an attachment for closed-chain training.

Special Considerations for Isokinetic Training

Availability of Equipment

From a pragmatic perspective, one limitation of isokinetic exercise is that a patient can incorporate this form of exercise into a rehabilitation program only by going to a facility where the equipment is available. In addition, a patient must be given assistance to set up the equipment and often requires supervision during exercise. These considerations contribute to high costs for the patient enrolled in a long-term rehabilitation program.

Appropriate Setup

The setups recommended in the product manuals often must be altered to ensure that the exercise occurs in a position that is safe for a particular joint. For example, even though a manufacturer may describe a 90°/90° position of the shoulder and elbow for strengthening the shoulder rotators, exercising with the arm at the side may be a safer, more comfortable position

Initiation and Progression of Isokinetic Training During Rehabilitation

Isokinetic training is begun in the later stages of rehabilitation, when active motion through the full (or partial) ROM is pain-free.

Buy the Book that holds this excerpt: Therapeutic Exercise: Foundations and Techniques (Therapeutic Exercise: Foundations & Techniques)

NOTE: All descriptions for hand placements are for the patient’s right (R) upper extremity. During each pattern tell the patient to watch the moving hand. Be sure that rotation shifts gradually from internal to external rotation (or vice versa) throughout the range. By mid-range, the arm should be in neutral rotation. Manual contacts (hand placements) may be altered from the suggested placements as long as contact remains on the appropriate surfaces. Resist all patterns through the full, available ROM.

D₁Flexion

Starting Position. Position the upper extremity in shoulder extension, abduction, and internal rotation; elbow extension; forearm pronation; and wrist and finger extension with the hand about 8 to 12 inches from the hip.

Hand Placement. Place the index and middle fingers of your (R) hand in the palm of the patient’s hand and your left (L) hand on the volar surface of the distal forearm or at the cubital fossa of the elbow.

Verbal Commands. As you apply a quick stretch to the wrist and finger flexors, tell the patient “Squeeze my fingers, turn your palm up; pull your arm up and across your face,” as you resist the pattern.

Ending Position. Complete the pattern with the arm across the face in shoulder flexion, adduction, external rotation; partial elbow flexion; forearm supination; and wrist and finger flexion.

D₁Extension

Starting Position. Begin as described for completion of D₁Flexion.

Hand Placements. Grasp the dorsal surface of the patient’s hand and fingers with your (R) hand using a lumbrical grip. Place your (L) hand on the extensor surface of the arm just proximal to the elbow.

Verbal Commands. As you apply a quick stretch to the wrist and finger extensors, tell the patient, “Open your hand” (or “Wrist and fingers up”); then “Push your arm down and out.”

Ending Position. Finish the pattern in shoulder extension, abduction, internal rotation; elbow extension; forearm pronation; and wrist and finger extension.

D₂Flexion

Starting Position. Position the upper extremity in shoulder extension, adduction, and internal rotation; elbow extension; forearm pronation; and wrist and finger flexion. The forearm should lie across the umbilicus.

Hand Placement. Grasp the dorsum of the patient’s hand with your (L) hand using a lumbrical grip. Grasp the dorsal surface of the patient’s forearm close to the elbow with your (R) hand.

Verbal Commands. As you apply a quick stretch to the wrist and finger extensors, tell the patient, “Open your hand and turn it to your face”; “Lift your arm up and out”; “Point your thumb out.”

Ending Position. Finish the pattern in shoulder flexion, abduction, and external rotation; elbow extension; forearm supination; and wrist and finger extension. The arm should be 8 to 10 inches from the ear; the thumb should be pointing to the floor.

D₂Extension

Starting Position. Begin as described for completion of D₂Flexion.

Hand Placement. Place the index and middle fingers of your (R) hand in the palm of the patient’s hand and your (L) hand on the volar surface of the forearm or distal humerus.

Verbal Commands. As you apply a quick stretch to the wrist and finger flexors, tell the patient, “Squeeze my fingers and pull down and across your chest.”

Ending Position. Complete the pattern in shoulder extension, adduction, and internal rotation; elbow extension; forearm pronation; and wrist and finger flexion. The forearm should cross the umbilicus.

LOWER EXTREMITY DIAGONAL PATTERNS

NOTE: Follow the same guidelines with regard to rotation and resistance as previously described for the upper extremity. All descriptions of hand placements are for the patient’s (R) lower extremity.

D₁Flexion

Starting Position. Position the lower extremity in hip extension, abduction, and internal rotation; knee extension; plantar flexion and eversion of the ankle; and toe flexion.

(NOTE: This pattern may also be initiated with the knee flexed and the lower leg over the edge of the table.)

Hand Placement. Place your (R) hand on the dorsal and medial surface of the foot and toes and your (L) hand on the anteromedial aspect of the thigh just proximal to the knee.

Verbal Commands. As you apply a quick stretch to the ankle dorsiflexors and invertors and toe extensors, tell the patient, “Foot and toes up and in; bend your knee; pull your leg over and across.”

Ending Position. Complete the pattern in hip flexion, adduction, and external rotation; knee flexion (or extension); ankle dorsiflexion and inversion; toe extension. The hip should be adducted across the midline, creating lower trunk rotation to the patient’s (L) side.

D₁Extension

Starting Position. Begin as described for completion of D₁Flexion.