Application of Elastic Resistance
Selecting the appropriate grade of material. The thickness (stiffness) of the material affects the level of resistance. A heavier grade of elastic generates greater tension when stretched and therefore imparts a greater level of resistance. As already noted, corresponding levels of resistance have been published for the different grades of bands and tubing.

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.

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