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.
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.
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.
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