Strength Training for Disabled Athletes

Thomas P. Dompier, MS, ATC, CSCS, ©2001

Abstract

            People with disabilities can benefit from resistance exercise programs.  With awareness of disability specific considerations, fitness professionals can apply the same principles of resistance exercise used when working with able-bodied people.  The principles of specific adaptation to imposed demands (SAID), progression, overload, volume, frequency, intensity, documentation, motivation, and specificity used with able-bodied people should be applied similarly in disabled people.  Awareness of disability specific limitations may require modification of the application of these principles.  Disabilities should be considered as progressive neuromuscular, non-progressive neuromuscular, or physical disorders.  The efficacy of resistance exercise has been debated in people with progressive disorders such as muscular dystrophy, and non-progressive disorders such as post-polio syndrome.  Current research has demonstrated that resistance exercise may be beneficial by slowing progression of the disease or retraining the neuromuscular system following atrophy.  People with hearing loss, blindness, amputations or intellectual disabilities do not have neuromuscular impairment, and should be trained no differently than an able-bodied person.  The only disorders in which there are clear contraindications are the more severe forms of osteogenesis imperfecta (OI) and Duchenne muscular dystrophy (DMD).  In conclusion, people with most disabilities can and should benefit from resistance exercise programs with the proper modifications based on disability specific limitations. 

Introduction

            The inception of participation in sport by people with impairments began when Sir Ludwig Guttman opened the first spinal cord injury unit in the Stoke Mandeville Hospital in England in 1944 (Guttman, 1966).  Sport participation was routinely used as an adjunct to physical therapy and eventually lead to the first National Stoke Mandeville games for the paralyzed in 1948 (Guttman, 1966).  The number of participants and the number of opportunities for people to participate in sport has steadily increased since the first Stoke Mandeville Games, and this increase has lead amplification of research in the physical development of athletes with impairments.  The purpose of this paper is to describe basic strength and conditioning principles and how these principles can be applied when specific impairments are present.

            Over 38 million Americans, approximately 15%, are classified as having some form of disability that limits activity levels (Kaye, Laplante, Carlson and Wenger, 1996; LaPlante, 1996).  Disability has been described as the resulting limitation in social or physical activities that are caused by chronic mental or physical health disorders, injuries, and impairments (LaPlante, 1996).  Impairments can be further defined as congenital or acquired deficits in the structure and or function of the human body caused by a present or previous injury or health condition (LaPlante, 1996).  These figures present the magnitude of the population who have some form of impairment, and the magnitude of those who may benefit from a sound resistance exercise program.  Resistance exercise can help people with impairments overcome some of the physical challenges they face. 

These challenges may include activities of daily living, mobility, and other tasks that facilitate autonomy.  Resistance exercise has many benefits for people with impairments ranging from increasing self-esteem, making transfers easier, facilitating the use of prosthetics and increasing strength and endurance for sport competition.  Baring any disability specific contraindications, most people can benefit from resistance exercise. 

Principles of Resistance Exercise

            Resistance Exercise can take many forms.  Some of the reasons people strength train include improving health, maintaining muscular endurance, bodybuilding or weightlifting competitions, and recreation.  The most common forms of resistance exercise include using free or machine weights, surgical tubing, body weight exercises, manual resistance, or any other form of activity that follows basic strength training principles.  These include specific adaptations to imposed demands (SAID), progression, overload, intensity, volume, individualization, variation and specificity. 

SAID Principle

            The SAID principle describes the adaptation that occurs within tissue when it is progressively overloaded (Wathen & Roll, 1994).  If a person physically stresses the body tissues such that they fatigue while performing an exercise, they will adapt to that stress so next time it will be better able to respond to that physical stress.  If this physical stress is repeated and increased, the body will continue to increase strength by adapting neurological pathways (Chestnut and Dockerty, 1999; Moritani and De Vries, 1979; Sale, 1987; Sale, MacDougall, Upton, McComas, 1983), increasing muscle size (Frontera, Meredith, O’Reilly et al., 1988; Hakkinen, Pakarinen, Kraemer, et al., 2001; MacDougall, Sale, Always, Sutton, 1984; MacDougall, Ward, Sale, Sutton, 1977), and increasing the mineral content of bone (Colletti, Edwards, Conroy, Kraemer, Maresh, Dalsky, 1992; Gordon et al., 1989; Layne and Nelson, 1999; Pinary, Bodeux, Crielaard, Franchimont, 1987). 

            Moritani and De Vries (1979) demonstrated that neural adaptation accounted for the majority of strength gain during the first 3 to 5 weeks of a resistance exercise program conducted on 7 males and 8 females.  That study also demonstrated the phenomenon of cross education in which both sides increase strength while only training one side.  The cross education phenomenon may be of particular interest to those with hemiplegia or other unilateral impairments.  In another study, Sale et al. (1983) demonstrated an increased reflex response as a result of resistance exercise. This study measured the effects of resistance exercise in 2 untrained females and 12 untrained males by measuring the reflex response in the upper limb.  The authors concluded that the increased strength of the reflex response is indicative of increased motor unit recruitment, thus, neurologic adaptation.  Although the majority of strength gain early in strength training programs can be attributed to neurologic adaptation, longer periods of strength training will cause muscle hypertrophy. 

            Increased muscle strength is the result of both neurological adaptation and muscle hypertrophy.  Muscle hypertrophy is the increase in the size of a muscle, and hyperplasia is the increase in the number of muscle cells.  Increased strength gains have been attributed to hypertrophy, but not hyperplasia as it is thought the adult number of muscle cells is reached in early childhood. 

            Increases in cross-sectional area of 5-23% have been demonstrated in studies lasting from 3 to 6 months (Frontera et al., 1988; Hakkinen et al., 2001; MacDougall et al., 1977).  These increases were attributed to increased fiber size but not number.  The volume of activity intervention, previous level of training, and the length of the training regimen can explain the large variability in muscle size increases.   In addition, MacDougall, Sale, Always, Sutton (1984) demonstrated that the biceps brachii in body builders were over 75% greater in cross-sectional area than untrained control subjects.  However, that study may have been confounded by the use of steroids in the bodybuilding group.  Nonetheless, MacDougall et al., 1984 using muscle biopsies demonstrated that the cross-sectional area of the muscle fibers increased in the same proportion as the entire muscle.  The authors concluded that the proportional increases cross-sectional area were evidence that muscle demonstrates hypertrophy and not hyperplasia.  Potteiger, Lockwood, Haub et al., (1999) found a similar relationship using plyometric training techniques.  Two groups participated in an 8-week 3 day-a-week plyometric training program.  Group one was plyometric training only versus group two who also had the added intervention of aerobic training.  Both groups showed an improvement in muscular power but neither improved more significantly than the other.  It is interesting to note that these increases in muscle size have been positively correlated to increased bone mineral density. 

            Colletti et al., (1989) demonstrated increased bone mineral density in the long bones of young males who participated in a resistance exercise program.  A relationship between the amount of strength and bone mineral density was shown.  Other studies have reported a similar correlation between increases in muscle size, skeletal girth and mineral content (Conroy, et al., 1992; Pirnay, et al., 1987; Layne and Nelson, 1999).  These adaptations occur during strength training as a result of the SAID principle, however, the adaptations produced as a result of the SAID principle cannot occur without the application of progression and overload. 

Progression

            Progression involves increasing the demands placed on the muscle during each training session.  This may include increasing the weight or increasing the number of repetitions of a previously used weight.  Either method is a form of progression.  As previously mentioned, progression is based on the SAID principle.  If a person continually performs the same amount of repetitions with the same amount of weight day after day, the body will adapt to that amount of work, but will no longer need to adapt to facilitate that exercise.  Progression will cause the body to constantly adapt to the increased demands by recruiting more neurological pathways and increasing muscle fiber size.  The efficacy of progression has been demonstrated in numerous studies.

            Holster, Crill, Hagerman, and Staron (2001) demonstrated the effectiveness of progression in two groups of men and women of over a 16-week period.  The purpose was to compare the efficacy of small weight incremental progressions (0.5 lbs) versus a more traditional progression of higher weights (2.5 lbs). Both progressive resistance methods proved effective, but neither was significantly more effective than the other. This demonstrates that as long as the principle of progression is followed, improvements in strength will occur.  Sanborn, Boros, Hruby, et al., (2000) found progression to be effective in a study of 17 untrained females.  Over an 8-week period two groups trained 3-days a week performing either one set to muscular failure or three sets not to failure.  If a target number of repetitions were reached the subject would increase the weight on the bar by 2.5 or 5 lbs increments.  Both groups demonstrated the efficacy of progression, but he latter was thought superior.  The principle of overload allows progression to be effective, without overload progression would have diminished results.

Overload

            Overload is achieved by progressively placing more stress on the muscle than it is generally accustomed to doing (Delorme and Watkins, 1948).  This can be accomplished by increasing the number of repetitions done per set or by increasing the number of sets performed in an exercise session.  On example would be an athlete who can lift 100 lbs for 10 repetitions, he would have to attempt more repetitions at the same weight or increase the weight for the same number of repetitions to cause an overload.  This principle directly corresponds with progression and is also dependant on volume. 

Volume and Frequency

            Volume is the amount of work done over time.  Volume is often measured by the number of sets per exercise, the number of exercises, or the number of repetitions during an entire workout.  The number of days during a week that resistance exercise is performed the frequency. McLester and Bishop (2000) demonstrated that when volume is held constant, strength training is more effective if done more frequently.  They compared two groups of men and women randomly assigned to a 1 day a week or 3 day a week training group.  The volume was held constant meaning that the group that only trained once a week did the same amount of work as the 3 day a week group.  The multiple days a week group demonstrated significantly higher increase in strength, but the 1-day a week group did show strength increases.  Hunter (1985) found that a simple alternating day frequency was less effective than lifting for three consecutive days and resting three consecutive days.  This demonstrates the need for adequate recovery periods, which may need to be longer than those of able-bodied people.  Volume and frequency are most often manipulated to vary the workout, but another principle that should be considered is exercise intensity.

Intensity

            Intensity is defined by work over time.  The more work that is performed in a shorter period of time, the more intense the workout.  An example would be an athlete who typically takes a 3-minute break between sets of exercises, decreasing that break to 1-minute would increase the intensity substantially. Conversely, the same amount of work could be done over a longer period of time, but the intensity is decreased.  Generally, a common method of increasing intensity is shortening the period between sets of each exercise.  In addition, super-sets (alternating sets of push & pull exercises) allow a person to move from exercise set to exercise set with very little time between them.  Alternating bench press with seated rows and moving from one to the other with little rest would be an example of a super-set. 

            In a study examining maximal effort resistance training with different loads, Moss, Refsnes, Abildgaard, Nicolaysen, Jensen (1997) concluded that maximal effort resistance training was an effective method of increasing strength.  There were three groups of physical education students, and each group trained at different percentages of the measured one repetition maximum. This included 90%, 35% and 15% of each student’s one repetition maximum.  Each of the groups showed improvement, demonstrating that various intensities are effective, but this study also demonstrated that load specificity is another important resistance training principle.

Specificity

            Specificity involves training the muscles in a fashion similar to that which the performance is based.  If a power lifter is expected to bench press a one repetition maximum in a competition than they should train with loads and intensities that are similar to those used in competition.  Moss et al. (1997) concluded that greater increases in a one repetition maximum in the group that trained at 90% of their one repetition maximum was the result of load specificity. However, improper application of specificity, and other principles, can also have negative effects on performance parameters. 

            If care is not taken to properly manage progression, volume, frequency and intensity, negative affects can occur.  Fry, Webber, Weiss, et al. (2000) demonstrated decreased performance in various activities following the application of a high intensity resistance exercise program.  Although a positive increase in strength was shown, performance decreased in activities not specific to the type and method of resistance training administered.  Care should be taken to assure that the resistance exercise program is not only specific to the person’s needs, but also to their disability.

Documentation and Motivation

            Documentation not only provides a record of a weight lifter’s accomplishments, it is also a source of motivation.  Documentation of sets and repetitions performed provides a record of the proper weight, the number of repetitions, and the number of sets performed from day to day for each exercise.  Documentation is also an important source of motivation because it illustrates improvements over time.  Motivation is important because it keeps people interested in achieving the goals they set out to accomplish.  Using a variety of exercises, sets and repetitions also helps to maintain motivation.  Resistance-training programs will be disorganized and frustrating without proper documentation and methods to maintain motivation.  Employing the principle of specificity is another method of maintaining motivation, but is also important in achieving the proper goals of a resistance exercise program.

Disability Specific Considerations

            People with disabilities can achieve the same benefits from resistance exercise that most other individuals can.  However, care must be taken to recognize specific considerations that people with each condition face.  These considerations range from simple logistical difficulties to life threatening conditions such as autonomic dysreflexia.  With these considerations, and others in mind, individuals with disabilities can achieve the same benefits and enjoyment from resistance training that their able bodies counterparts can. 

Vision and Hearing Disabilities

            People can have limited eyesight and hearing due to congenital or acquired conditions.  However, these same people have the same physical capacity as able-bodied individuals.  A few simple modifications should be considered when working with these populations.  When working with blind athletes it is important for fitness professionals to make sure no weights, bars or other objects a person may trip over are left on the ground.  Blind people may also need initial orientation to the layout of the facility and instruction on proper hand placement or body position during some of the exercises.  Verbal descriptions of the exercises and proper techniques will facilitate instruction.  No equipment modifications or modifications to exercise principles are needed with this population, but good communications skills on part of the fitness professional will aid in the enjoyment and efficacy of the program.  Similarly, deaf people do not have any physiological or physical limitations and can also benefit from resistance exercise programs.  

            People who are deaf are also able-bodied and do not need modifications to the resistance training principles.  However, some basic accommodations should be considered.  Fitness professionals should cooperate with the individual in developing hand signals for the purposes of instruction, safety, and motivation.  Demonstration of technique may be the most efficient way of instructing deaf people, and hand signals can express encouragement or directions.  With these simple considerations in mind, deaf people can benefit from and enjoy resistance exercise. 

Through simple tasks such as keeping the fitness area tidy and developing hand signals, blind people, deaf people and fitness professionals can have a productive and rewarding exercise experience.  Both of these populations can follow the same resistance exercise principles that able-bodied people do, and no modifications of existing equipment or philosophies are necessary.  However, this may not be the case with specific non-progressive and progressive disabilities of the neuromuscular system. 

Non-progressive Disabilities to the Central Nervous System

            The central nervous system (CNS) monitors and controls all bodily functions including movement.  The CNS is the most complex and least understood component of human anatomy, and includes the spinal cord, brain and related structures.  Non-progressive disorders that can affect the CNS include intellectual disability (ID), cerebral palsy (CP), stroke, traumatic brain injury (TBI), spinal cord injury (SCI), spina bifida (SB), post-polio syndrome (PPS), and myasthenia gravis (MG).  Disabilities of the CNS can take many forms, but most individuals with a moderate to high functional capacity can benefit from resistance exercise. 

            Intellectual disabilities. Two of the most commonly recognized intellectual disabilities include autism and downs syndrome, but ID can also be present in other forms.  People with ID can benefit from resistance training for a couple of reasons.  First, people with ID have a higher prevalence of obesity than do non-ID people (Burkart, Fox, Rotatori, 1995).  People with ID have also been shown to age faster causing a more rapid decline in physical abilities (Pitetti, Campbell, 1991).  These two reasons alone warrant physical activity as an intervention needed in people with ID.  However, even though physical activity is warranted, the method or degree of improvement in this population has been debated (Chanias, Reid, Hoover, 1998).  

            In a meta-analysis of 21 studies involving ID subjects, Chanias et al. (1998) found that there was no significant effect size (ES) for changes in body composition, small ES for flexibility, only moderate ES in strength, and large ES in muscular and cardiovascular endurance.  Chanias et al. (1998) noted the weakness of the previous studies and concluded that further research must be conducted on each of these fitness parameters in people with ID.  It is important to note that the studies examined in the Chanias et al. (1998) analysis varied greatly in methodology and protocol, but most showed some improvement in the fitness parameters measured.  Therefore, it is reasonable to conclude that people with ID can benefit from resistance training, although the most effective means and methods have yet to be determined. 

            Cerebral palsy. Cerebral Palsy (CP) is caused by damage to the motor neurons within the brain, and can be congenital or acquired.   There are several forms of CP, each with different symptoms, but similar characteristics.  Symptoms include chronic muscle spasm, hypotonicity, weakness, and impaired movement control (DiRocco, 1995).  The six forms of CP include spastic, athetoid, ataxia, rigidity, tremors, and mixed.  Spastic CP is the most common and affects approximately 60-70% of all people with CP (DiRocco, 1995).  This form of CP causes chronic muscle spasm of the flexor muscles primarily, and can severely limit movement.  Athetoid CP is characterized by involuntary fluctuations in muscle tone and movement patterns, and is the second most common form (DiRocco, 1995).  Ataxia is characterized by impaired balance and gait patterns, people with ataxia have little muscle tonicity.  A rare form of CP is characterized by rigidity and tremors.  People with this form often have severe postural limitations and may have severe mental retardation (DiRocco, 1995).  There is no cure for CP. Therefore, treatment is designed to improved quality of life by reducing symptoms and avoiding complications.  

            People with CP have impaired neurological control of movement, but the muscle itself is unaffected by CP.  Therefore, people with CP can obtain the same benefits from resistance exercise as able-bodied people.  The specific disorder and level of severity will determine the amount of movement restriction that exists and each resistance exercise program should be tailored to the specific individual needs of each patient. 

DiRocco (1995) recommends avoiding excessive fatigue to avoid causing further deterioration of movement patterns.  This can be done by using longer rest periods between sets, avoiding fast movements and avoiding unexpected excitement (DiRocco, 1995).  DiRocco (1995) also recommends allowing people with CP to have an exaggerated warm-up of 15-20 minutes utilizing large, slow and rhythmical movements.  Stretching is also an integral part of warm-up for people with CP.  Because of the spastic tonicity present in many forms of CP, patients will benefit from stretching before and after resistance training.  Stretching should be used to help facilitate normal ROM and function.  People with athetoid CP should be encouraged to focus on relaxation because they are constantly in spasm and will benefit from the reduction of stress.  Those with ataxia should be monitored carefully because of the difficulties with coordination and movement patterns. 

Damiano, Vaughan, Abel, (1995) studied the effects of heavy resistance exercise in 14 children with spastic cerebral palsy.  These results were compared to a control group of 25 able-bodied children.  Both groups performed knee extension exercises three times a week for six weeks.  The results demonstrated that quadriceps strength increased in both the CP and control groups.  The authors concluded that resistance training is beneficial in restoring or maintaining mobility in people with CP.  This study demonstrates that those with CP can benefit similarly to those without, but nevertheless, consideration must be given to each individual’s impairments and abilities.

As mentioned, care should be taken to avoid excessively fatiguing people with CP.  Modification of workout intensity should be performed to avoid excessive fatigue initially, but more typical intensities may be implemented after a period of neuromuscular adaptation.  Excessive spasticity may also require that stretching exercises be performed after each exercise or set.  Resistance exercise may increase spasticity, therefore, efforts should be made through stretching and modification of workout intensity to decrease the chances of this from happening.  The principles of volume and frequency may also require modification.  Those with CP may require longer recovery periods initially to alleviate fatigue and soreness.  Nevertheless, the principles of progression, overload, specificity, motivation and documentation should be followed to ensure a beneficial effect in people with CP. 

Stroke and traumatic brain injury. People who suffer a stroke or traumatic brain injury can have a wide range of post event impairments depending on the location of the brain damage.  This damage may be permanent or temporary.  Impairments can include brain centers that control language, spatial orientation, behavior, paralysis, speech, and memory (DiRocco, 1995).  Strokes occur because of hemorrhage or lack of oxygen to the brain.  Similarly, head injuries can also cause brain damage due to oxygen deprivation or hemorrhage. 

            The nature of such conditions requires that people who suffer a stroke or traumatic brain injury have a complete physical and a physician’s approval to begin a resistance exercise program.  However, if resistance exercise is indicated as an adjunct to rehabilitation, then care must be taken not to excessively increase blood pressure.  It is the responsibility of the fitness professional to make sure the patient understands proper technique and breathing principles.  Other considerations include memory problems, paralysis and difficulties with spatial orientation.  People with memory deficits may require extra time be spent retraining them to perform various exercise.  People who have paralysis may need assistance with transfers from a wheel chair to the bench, and people with spatial orientation problems should be closely spotted.  These same issues should be considered in a spinal cord injured population. 

            Spinal cord injury and spinal bifida. Injury to the spinal cord can affect a person’s mobility and autonomy.  Inactivity that often accompanies spinal cord injury can also lead to secondary health problems such as cardiovascular disease.  Resistance exercise is important in maintaining and regaining strength following spinal cord injury, but also helps to regain mobility, autonomy and to maintain fitness levels.  Regaining mobility, autonomy and fitness levels can be facilitated with the incorporation of resistance exercise.  Resistance training has been shown to have positive effects in people with spinal cord injuries (SCI) and spina bifida.

            O’Connell and Barnhart (1995) examined the effects of resistance exercise in 3 children with cerebral palsy and 3 children with myelomeningocele, a form of spina bifida.  Subjects exercised their upper bodies 3-days a week, and completed three sets of six repetitions at each session.  This program was followed for a period of 8-weeks and consisted of circuit type training regimen with little rest between sets.  Each child performed wheelchair propulsion tests consisting of a 50-meter sprint test and a 12-minute distance test before and after the training intervention.  Subjects also participated in a 6 repetition max test for each of the strength measures.  Subjects significantly improved the 12-minute distance test and strength tests, but non-significantly improved in the 50-meter sprint test.  O’Connell and Barnhart (1995) concluded that resistance exercise is beneficial for people with cerebral palsy and myelomeningocele who use wheelchairs. 

            In another study, Davis and Shephard (1990) investigated the effects of resistance exercise in 15 sedentary adult males with SCI.  Participants were randomly assigned to one of four exercise regimens using an upper body ergometer.  These regimens included intensities of 70 or 40 percent of maximal oxygen uptake and training sessions of either 40 or 20 minutes in length.  Peak power, average power, total work, and muscular endurance were measured before and after the 16-week intervention using a Cybex II dynamometer.  The results demonstrated that power increased in both shoulder extension and elbow flexion, and these gains were higher in the group that exercised at the highest intensities and length.  These results should be considered carefully however, as the results were not significant and the subject pool was small with 11 subjects and 4 controls.  Invariably, some of the initial increase in power measured in these subjects was the result of neuromuscular adaptation as seen in the early stages of resistance exercise programs, and would therefore weaken the results of this study further.  Another shortcoming is the lack of specificity in the training regimen.  The upper body ergometer is not specific for developing power at the intensities and length of workouts prescribed.   Although this study has shortcomings, it demonstrates a non-significant increase in power in individuals with SCI. 

            Other studies examining resistance exercise in person with SCI and spina bifida vary in methodology and quality, but the evidence that does exist demonstrates that this population can and should benefit from resistance exercise programs (Billow, 2001; Davis, Kofsky, Kelsey Shephard, 1981).  Care must be taken to have an awareness of possible complications in this population as with all disabilities.  Spinal cord injured people with injuries above thoracic vertebra 6 (T-6) can be at risk for developing a condition known as autonomic dysreflexia (DiRocco, 1995).  This condition is marked by a sudden and rapid increase in blood pressure, and can lead to cardiovascular complications if medical attention is not sought immediately at the onset of symptoms.  Symptoms include impaired sweating, headache, nasal constriction, goose bumps, and splotching of the skin, and is spurred by failing to empty the bladder at appropriate intervals (DiRocco, 1995).  As will all physical impairments, care must be taken to assess each person’s limitations and possible complications before engaging in a resistance exercise program.  

            Post-polio syndrome. Post-polio syndrome follows a bout of polio caused by a virus that attacks the neuromuscular system.  Symptoms of polio often include respiratory disorders, cardiovascular disorders, paralysis, muscle atrophy, structural deformities, or any grouping of these conditions (DiRocco, 1995).  People with polio often use leg braces or wheelchairs for mobility.  Post-polio syndrome has symptoms that include muscle fatigue, pain, decreased workload, and decreased strength (DiRocco, 1995).  DiRocco (1995) recommends resistance exercise only for muscles with no clinical symptomology, but does stress the need for muscular balance.  Conservative exercise programs with gentle stretching exercises were also recommended for people with post-polio syndrome.  However, this recommendation has been challenged in recent studies, and more intensive exercise programs may have benefits for post-polio survivors. 

            A study by Klein, Whyte, Keenan, et al., (2000) demonstrated an increased rate of strength loss in post-polio survivors.  In that study, one hundred and twenty men and women with post-polio syndrome were followed longitudinally for 9-months.  After 9-months, the post-polio survivors had lost strength at a rate faster than that expected with normal aging.  This increased rate in deterioration was not related to age, time since polio, gender, symptoms, or history of residual weakness.  It is unclear if the faster rate is the product of the polio itself, or the sedentary habits that are often present in post-polio survivors.  One indication of a sedentary lifestyle is the fact that there was little or no strength loss in the postural muscles of the survivors.  This would indicate that muscle strength could be maintained as long as the muscle is stressed, and the strength loss that does occur is the result of little use.  These results suggest that resistance training is indicated as a therapy for post-polio survivors, and other studies have sought to demonstrate the beneficial effects.

            Agre, Rodriquez, Franke, (1997) studied the effects of a 12-week home resistance exercise program in 7 subjects with post-polio syndrome.  Subjects performed 3 sets of 4 repetitions of maximal isometric quadriceps contractions 2-days a week for the duration of the study.  The results demonstrated that a home resistance exercise program could significantly improve strength in post-polio survivors without causing adverse effects.  It should be noted however, that there was no follow-up and it is uncertain if there were any long-term negative effects as a result of this program.  Nevertheless, this study does highlight the fact that resistance exercise can be beneficial in post-polio survivors.           

            As with CP, post-polio survivors may experience excessive fatigue initially, but there is not sufficient evidence to determine if this is the result of a sedentary lifestyle or a long-term complication exacerbated by resistance exercise.  Control of workout intensity, volume and frequency may help to diminish some of this effect. 

Myasthenia gravis. Myasthenia gravis (MG) is a disorder of the autoimmune system.  The antibodies of the person affected with MG attack the neuromuscular junction at the motor endplate and affect neuromuscular transmission.  The disease is characterized by muscle weakness and fatigue, and may affect any muscle in the body.  Recently, studies have shown that people with MG can benefit from resistance exercise programs.

            Stout, Eckerson, May et al. (2001) reported a case study on the effects of resistance exercise and creatine supplementation in a single subject with MG.  The subject self-administered 5 grams of creatine per day and performed resistance exercises 3 times a week for 15 weeks.  After the 15-week intervention, the subject increased leg extension and leg flexion strength by 37% and 12.5% respectively.  Although the authors conclude that resistance exercise in combination with creatine supplementation increased strength, there were no controls for comparison.  A control comparison would likely have shown that strength would increase following a resistance exercise program even in the absence of creatine supplements.  Any difference between the two groups could then be compared for statistical significance.  The research concerning creatine supplementation is lacking, and sufficient longitudinal studies demonstrating the long term health effects of creatine supplementation do not exist in able bodied people, much less those with neuromuscular disorders. 

            One of the symptoms of MG is fatigue and modification of workout intensities and frequencies may be necessary.  However, muscle weakness is also a symptom and therefore, warrants resistance exercise as an adjunct to rehabilitation.  Following the basic principles and modifying the intensity as necessary will allow people with MG to enjoy the benefits of resistance exercise.  

            Individuals with non-progressive neuromuscular disorders can benefit from resistance exercise programs.  Consideration must be given to each person and condition on an individual basis, and people with non-progressive neuromuscular disorders should always consult their physician before beginning any resistance exercise program.  Fatigue must be a consideration when working with individuals with CP, MG, and post-polio syndrome.  Modification of workout intensity, duration and frequency may be necessary, but should not exclude them from participation.  Although resistance exercise is thought beneficial for non-progressive disorders, the research surrounding progressive neuromuscular disorders is not as clear.

Progressive Neuromuscular Disorders

            Progressive neuromuscular disorders are those diseases that have symptoms that worsen overtime at varying degrees and rates.  The two most prevalent forms are multiple sclerosis (MS) and muscular dystrophy (MD).  Both disorders involve the neuromuscular system, but MS specifically involves the white matter of the nervous system and MD involves destruction of muscle cells.  Resistance exercise as an adjunct to physical therapy for MS and MD patients has been debated. 

            Multiple Sclerosis. Multiple sclerosis (MS) is a progressive disease that causes demyelination of nerve axons.  In the United States, MS affects nearly 250,000 people (Ponichtera-Mulcare, 1993).  Demyelination causes degenerative neuromuscular control and symptoms that can include ataxia, weakness, fatigue, spasticity, hypersensitivities to heat and cold, sensory disturbances and others.  People with MS can benefit from resistance exercise, but the exercises that will be the most beneficial will be based on the symptomology they present. 

            Lambert, Archer, Evens, (2001) demonstrated that people with MS have less muscular strength and fatigue quicker than able-bodied controls.  Two groups of 15 subjects were compared for knee muscular strength and endurance.  Individuals with MS demonstrated less muscular strength and greater fatigability.   The results of this study were likely confounded by the more sedentary habits of the people with MS prior to the study, but demonstrate the need for resistance training in this population.  

            Gehlsen, Grigsby, Winant, (1984) measured the effects of resistance training in people with MS.  Ten subjects performed aquatic based resistance exercises 3 days a week for 1 hour over a 10-week period.  Pre, mid and post measurements were taken, but no control group was used for comparison.  Subjects showed improved strength in both the upper and lower body during the mid intervention measures, but only the upper body strength improved significantly more from mid to post measure.  From this investigation, the authors conclude that people with MS can benefit from a resistance exercise program.  However, the efficacy of the intervention used in this study cannot be determined without the existence of a control group, and long-term effects that this intervention may have had are also unknown.  

            People with MS have a need for and can benefit from resistance exercise, but little research exists on the mode, frequency and efficacy.  The progressive nature of MS cannot be stopped or reversed, but resistance training can help to maintain function for a longer period of time and prevent complications associated with sedentary lifestyles (DiRocco, 1995).  Little research exists on the long-term effects of resistance training in people with MS, and future research should seek to validate training regimens and examine positive and negative long-term effects in people with MS.  In addition, modification of existing conditioning principles may be necessary to avoid initial fatigue and soreness.

            Muscular Dystrophy.  The use of resistance exercise as an adjunct to physical therapy in people with MD has also been debated.  The matter is complicated by the existence of multiple forms of the disorder.  Two of the most prevalent forms include Becker muscular dystrophy (BMD) and Duchenne muscular dystrophy (DMD).  The latter is considered the more severe form of MD, and resistance exercise has been contraindicated.  People with DMD rarely live beyond the mid-twenties.  In both BMD and DMD, the use of resistance exercise has been debated based on assumption that resistance exercise would exacerbate symptoms.

            Current research has supported the use of resistance exercise in patients with various forms of DMD.  Kilmer, Aitkens, Wright, McCrory, (2001) demonstrated a similar response to eccentric exercise in people with MD compared to those without the disorder.  These studies investigated these effects in nine subjects with myotonic MD, two with fascioscapulohumeral MD, and one with Becker MD, and were compared against eighteen able-bodied controls.  Physiologic responses were found to be similar in subjects and controls, but the soreness response was non-significantly better in the control group.  Although similar results were found, the authors concede that no long-term effects were measured, and the increased soreness in the intervention group could be attributed to a prior sedentary lifestyle. 

In a case-report of a single female with Duchenne muscular dystrophy, Bohannon and Jones (1986) reported a 28% increase in strength bilaterally following a 12-week resistance exercise program.  No long-term effects were reported and it is unclear if the authors performed a long-term follow-up to assess possible negative consequences of the intervention.   Milner-Brown and Miller (1988) also demonstrated increases in strength following resistance exercise with up to 3-4 years of follow-up measures.  In that study, 16 patients significantly improved their strength over the course of the study, and did not demonstrate long-term negative affects sometimes attributed to resistance training.  It should be noted, however, that none of those patients were classified as having Duchenne MD. 

New evidence demonstrates that previously contraindicated resistance exercise may be beneficial in people with MD. Nevertheless, care should be taken to consult each person’s physician prior to beginning any exercise program.

Bone and Joint Disabilities

             Osteogenesis Imperfecta. Osteogenesis imperfecta (OI), or brittle bone disease, is a congenital condition that affects individuals of all races, genders and ethnic origin (Byers and Steiner, 1992).  It is a very rare disease affecting only 1 in 5000 to10, 000 individuals (Byers and Steiner, 1992).  Osteogenesis imperfecta can be classified into six different subtypes, all of which are of the non-lethal variety (Engelbert, van der Graaf, van Empelen, et al., 1997).  The most common and least serious form is type I.  This group is characterized by osteopenia (bone mineral deficit).  Osteopenia causes them to suffer multiple bone fractures, joint laxity, and dental cavities.  More severe subgroups of the disease are marked by multiple fractures, progressive deformity of the bones, joint laxity, and severely reduced height.  These symptoms would require special consideration when considering a resistance exercise program.  DiRocco, (1995) advocates resistance training for people with OI to improve joint stability, but warns to prevent excessive stress or impact on the bones as these may cause further impairment or fractures.  DiRocco, (1995) further recommends water aerobics or exercise to help maintain fitness, but this would only apply to those most functional and tolerant of that amount of stress.  Special consideration must be give to people with OI, but people with milder forms of the disease can tolerate and benefit from low stress and low impact conditioning programs such as water aerobics.

            Amputation. People with an amputation are able-bodied people with the absence of a limb.  Therefore, there is no physical or physiological reason this population cannot enjoy the benefits of a resistance exercise program.  Many amputees are routinely involved in sport, and with the advance in prosthetic technologies; more amputees are becoming increasingly involved in sport.  Simple modification may be necessary depending on the level and location of the amputation, but may also require special equipment or modifications.  People with multiple amputations may need added assistance of fastening devices to either hold on to the bar or keep the person stabilized on the bench or rack.  Although the muscle physiology of amputees is normal, those with multiple amputations may have impaired thermoregulation. 

Care should be taken to make sure the amputee does not suffer from heat illness.  The facility in which the amputee is exercising should be well ventilated and kept at a moderate temperature.  Water should also be readily available and extended rest may be required between sets to allow the person’s body temperature to lower.  The principles of resistance exercise can be applied in programs which amputees participate, but considerations for equipment and thermoregulation should be kept in mind.  Intensity level should be monitored, but not modified unless the person has prior history of heat illness or begins to develop symptoms. 

Arthritis. Resistance training and other forms of exercise are at the center of debate amongst professionals researching the effects of exercise in people suffering from arthritis.  Arthritic conditions are any disorder that causes inflammation within the joints.  There are nearly 100 different types or arthritis (DiRocco, 1995).  The most common forms of arthritis are osteoarthritis and rheumatoid arthritis.  Rheumatoid arthritis is an autoimmune disease that causes the destruction of articular structure and thickening of the articular capsule.  Osteoarthritis is a degenerative joint disease in which overuse causes a breakdown of the articular cartilage.  Osteoarthritis is common among those who use wheelchairs, crutches or walkers to ambulate.  Only recently have healthcare professionals begun to realize the benefits of exercise for people with arthritis. 

            The disability associated with arthritis is usually a result of the inflammation within the joint.  The inflammation causes pain and joint stiffness, which in turn, leads to muscle tightness surrounding the joint.  Inactivity leads to further stiffness and disability because the inflammation will tend to accumulate within the joint without the muscle pumping action of movement.  In a comparison of high and low intensity training regimens in 100 rheumatoid arthritis patients, van den Ende, Hazes, Cessie et al. (1996) found that intensive dynamic activity lead to greater increases in aerobic capacity, joint mobility, and muscle strength.  In another study, Deyle, Henderson, Matekel, et al. (2000) found that osteoarthritis patients that exercise were 15% less likely to have knee surgery than the non-intervention group who did not exercise.  These studies support the assertion that even resistance and other forms of exercise are beneficial in arthritis patients. 

Conclusions

            Current research has shown the beneficial effects of resistance exercise in people with disabilities.  These benefits have even been demonstrated in people with disabilities in which resistance exercise was previously contraindicated.  However, it should be noted that long-term effects of resistance exercise in some disabilities have not been studied adequately and care should be taken to consult a physician prior to beginning any form of exercise. 

            Fitness professionals should be aware of each disability specific limitations, and should work with each person on an individual basis.  The person with the disability is often the best source of disability specific information.  However, if the person is also unsure of specific limitations, their physician should be consulted.      

            People who are visually and hearing disabled are able-bodied and have no physical limitations.  These populations can participate in all forms of resistance exercise programs.  Those with non-progressive disabilities can also benefit from resistance exercise, but individual consideration must be given to each specific disability.  Of the progressive disability types, muscular dystrophy is the disability in which the research is inconclusive.  Although current research has demonstrated the positive effects of resistance exercise in people with muscular dystrophy, there is not sufficient research of possible long-term effects of such programs.  Also, people with CP, MG, or post-polio syndrome may experience undue fatigue and intensity levels should be modified.  However, it remains unclear if resistance exercise has any long-term negative effects in progressive or non-progressive disorders, and care should be taken to consult the appropriate physician when there is any uncertainty.

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