Strength and age
IntroAging is inevitable. At a certain point, we all reach our physical plateau, and everything is downhill until we hit the bottom. However, we can do things to slow the rate of deterioration and we can still do a lot of the things we have always done; we just must make a few changes in the way do them.
Deterioration of skeletal muscle and its neural inputs begins between the ages of 50 and 60 years. Much of deterioration of skeletal muscle observed may be a result of inactivity, rather than age itself.
AnatomyLimitation in the range of motion of different joints is a problem in older persons due to many factors, such as joint misalignment, shortening of ligaments, or loss of elasticity in tendons. All these processes may affect strength since they change the leverage component of the joints.
Muscle strengthMuscle strength appears to be relatively stable through 50 years of age. A 15% loss in muscle strength per decade occurs between the ages of 50 and 70 years of age. From the ages of 70 to 80 years, a 30% loss in muscle strength can occur. Postural muscles, such as the quadriceps and soleus, show age-related atrophy to a greater extent than non-postural muscles. This decrease in muscle strength leads to a decreased ability to engage in physical activity.
The decline in muscle strength may have important functional consequences. The decline in strength in muscles of the lower extremities may be associated with gait disorders, falls, and hip fractures. A reduction in upper body strength increases the risk of accidents in activities that require lifting, pushing, or pulling maneuvers (such as housekeeping, cooking, and eating). A weakness of low back muscles may be related to problems such as disk herniation and chronic low back pain of soft tissue origin.
The prevalence of common chronic diseases in the elderly population is high. Illnesses affecting the musculoskeletal system, the heart and circulation, and the kidneys may be associated with muscle atrophy and weakness.
Older persons who remain physically active have only moderate losses in skeletal muscle mass, but exactly how much of the decrease in muscle is a consequence of aging or a reduction in physical activity or specific types of activity, or both, is currently unknown.
Training has effects on the physical capacity of older persons irrespective of whether they trained in youth. Older adults have much to gain by exercising. Martial arts instructors can teach their older students how to safe and effective train.
Strength trainingAging affects almost all the factors of muscle strength. Since these age-related changes are like some of the effects of inactivity, it has been postulated that they are partly due to lack of physical activity and not to the aging process itself. If this is true, it can be suggested that strength training may slow down or reverse some of these alterations.
Muscle can only contract three ways:
- Concentric contraction. A muscle can do the obvious and contract to shorten the distance between joints, such as when doing a bicep curl. This is called a concentric contraction, where the muscle tenses while shortening.
- Eccentric contraction. A muscle can also tense while lowering a load, or resisting it, such as when lowering the weight in a curl. This type of contraction is known as eccentric contraction and occurs when the muscle tenses while lengthening.
- Isometric contraction. A final type of contraction is called an isometric contraction. It occurs when the muscle tenses while not changing length. Examples of this are poses in bodybuilding or pushing against an immovable object such as a wall.
Types of strength training
ResistanceResistance training is any form of exercise that forces your skeletal muscles to contract. An external resistance (such as a heavy weight) is used to cause the contractions A program of regular resistive training, carried out over an appropriate period, can lead to larger muscles, increases in strength, alterations in body composition, hormonal and neural adaptations, and changes in cardiovascular capacity.
IsometricIsometrics training is a form of static exercise. Examples include the plank, the wall sit, and many yoga poses such as chair and tree poses. The problem with isometrics is that since the joints aren’t moving, there can be a decrease in coordination and speed of movement and a decrease in muscle elasticity. The advantages of isometric exercise lie in its brevity, its lack of special equipment needs, and its effectiveness.
IsokineticIsokinetic training uses specialized exercise machines that produce a constant speed no matter how much effort you expend. These machines control the pace of an exercise by fluctuating resistance throughout your range of motion. It offers subjects the advantage of seeing an immediate display of their performance. However, this type of exercise has not been fully investigated for the elderly. A major disadvantage is a need for special equipment.
EccentricEccentric training refers to any movement that lengthens a muscle at the same time it is being contracted. It is a braking force that directly opposes the shortening of a muscle (known as a concentric contraction). For example, as you lower your arm in a biceps curl, that lengthening movement would be considered eccentric. The lifting of the weight would be concentric. The disadvantage of eccentric training is that muscle soreness in the early part of the program does not allow rapid and progressive increases in resistance.
Things to considerNo matter which training program is used, several training elements need to be considered. To obtain a training effect in muscle, an exercise overload must be applied. Adaptations of muscles to training are related to the type, intensity, and duration of the training and the type of muscle being exercised. The extent of training is, at least in part, a function of the pre-training state of the muscles being used in the exercise.
Adaptations to trainingSkeletal muscle adaptations to exercise training and the improvement in muscle force production can be related to changes that occur within the muscle and/or the nervous organization of muscle contraction. Specifically, improvements in muscular strength are the result of structural changes in muscle and are due to neural adaptations that typically account for strength gains during the early part of the training. Increases in skeletal contractile proteins and anaerobic capacity are examples of muscle structural changes that occur with resistive training.
Training responsesEarly studies involving the ability of older people to adapt to resistive exercise indicated that 12 to 26 weeks of resistive exercise training elicited only minimal improvements in muscle strength of men and women between the ages of 60 and 75 years. Recently, muscle rehabilitation programs for well, older populations have shown significant increases in muscle strength, muscle volume, and other parameters of muscle structure and function. Studies have documented that, given an adequate training stimulus, older men and women show similar or greater strength gains compared to young individuals after resistive training.
It has been suggested that lack of muscle loading could contribute to muscle atrophy in the aged since individuals aged 60-90 years can increase/maintain muscle mass with resistance training. Men, who are 70 years of age who have resistance-trained since 50 years of age, had muscle cross-sectional area and strength comparable to a group of 28-year-old sedentary subjects. These findings were also compared with three groups of 70-year-old subjects (sedentary controls, swimming trained, or running trained) who all had a 20-24% decrease in muscle cross-sectional area and strength.
RecommendationsThe first step in beginning an exercise program for older adults is to consult with your doctor. To be successful, any exercise program must be effective, safe, and have some motivational appeal for the participant. To be effective and to achieve the physiologic benefits, an exercise routine must be of appropriate mode, duration, frequency, and intensity.
The resistance training protocol that has been shown to produce the greatest increases in muscle strength and attenuated atrophy to the greatest extent in older adults is three sets of eight repetitions of exercise performed at and 80% intensity, three days a week for 12 weeks. Training of older muscle can be initiated at a 50% to 60% intensity for one week and then increased to 80% intensity for the remainder of the training period.
Throughout the training period, maximum training loads need to be reestablished regularly.
Any exercise routine should include warm-up and cool-down periods, proper stretching exercises, and be designed to progress slowly in intensity. Programs should be individually tailored to the needs and interests of participants. Older adults also should be instructed to exercise in well-lighted and uncrowded areas without noisy distractions.
An exercise routine must have some motivational appeal if seniors are to adhere to it long enough to achieve the desired results. A program with incremental, achievable goals and a mechanism to measure progress is likely to encourage participation. Successful classes often use wall charts, individual records, or even computer programs to track progress. Perhaps of even greater importance is the ongoing assessment of the participant's response to exercise, including monitoring for changes in balance, strength, and flexibility, as well as any symptoms of adverse responses like pain, dyspnea, dizziness, or irregular heartbeats.
Exercise programs for older individuals must be safe as well as effective. Simple instructions by therapists can help seniors avoid injury while beginning an exercise program. Proper shoes with adequate cushioning and nonstick soles are essential for most activities.
During high-intensity resistance training, older persons should be continuously monitored for heart rate, blood pressure, and any signs or symptoms of distress. Older individuals should also be cautioned to avoid performing Valsalva maneuvers during exercise periods, as this maneuver may place strain on the individual's cardiovascular system. A Valsalva maneuver is when you use a moderately forceful attempted exhalation against a closed airway, such as a closed airway grunt.
SummaryA decline in muscle strength can no longer be considered an inevitable consequence of the aging process. Strength training induces changes in muscle and neural control mechanisms. The nature of the training response in the elderly depends on intensity and type of training. The benefits of maintaining or improving strength in the elderly may include correction of gait disturbances and safer ambulation, prevention of falls, reduction in bone fractures, improved mobility and stamina, improved performance of activities of daily living, and increased capacity for independent living.
- Tackett, C. (2003). Factors Affecting Strength.