Health and Fitness Information for Mature Adults 

August 1, 2008              

Table of Contents

  • Sarcopenia (Introduction to special issue)
  • A Loss of Muscle, Strength, and Function (Understanding sarcopenia)

Sarcopenia

Until recent years, most dictionaries and reference works did not even include the word sarcopenia. Yet most senior fitness professionals today are acutely aware of the term. Let us take a closer look at its etymology, definition, and implications.
 

A Loss of Muscle, Strength, and Function

Sarc, and sarco, derive from the Greek form sarko, meaning flesh. The suffix -penia traces back to New Latin which, in turn, stems from the Greek penia, meaning poverty or lack. Modern authors describe sarcopenia not only as an age-related deficit of skeletal muscle mass, but also as an accompanying loss of muscular strength and function. These factors intertwine in several respects:

  • Loss of muscle mass is associated with loss of strength.
  • Loss of strength is associated with loss of muscular function.
  • Loss of muscle mass and strength is associated with deteriorating general health.
  • Loss of muscle mass and function is associated with the progression of disease and with eventual disability.

Variables other than physical inactivity (such as hormonal changes and suppressed protein synthesis) may play a role in the development of sarcopenia. However, adopting a sedentary lifestyle is a major contributor to the condition -- and one that individuals can readily address. Indeed, sarcopenia is partially reversible given effective exercise training.

As mentioned above, sarcopenia is more than simple muscle loss. Furthermore, it should not be confused with disease-related declines in muscle mass. For example, sarcopenia differs from wasting, which depletes both muscle and adipose tissue consequent to the insufficient dietary intake resulting from certain diseases. Conversely, sarcopenia can appear in individuals unaffected by other conditions that characteristically lead to muscle loss.

Instead, sarcopenia typically arises during the fourth decade of life, accelerates after the age of 50, and may advance even more rapidly after the approximate age of 75. With normal aging -- and even more dramatically with inactive aging -- there is a decline in the number of motor neurons that control muscular action. Skeletal muscle fibers that are subject to those nerve cells can atrophy and ultimately die, thereby reducing muscle mass. Predominantly, atrophy has been observed to occur in fast twitch fibers (used for high-intensity movement). When a fast twitch motor neuron expires, a neighboring slow twitch motor neuron may step in to serve the affected muscle fibers, which will forestall atrophy. However, such remodeled motor units can be predicted to produce less force, slower movement, and decreased movement control. Reductions in balance and movement speed indicate a need for safety awareness during fitness training activities undertaken to counter sarcopenia.

Another source of muscle loss in sarcopenia is an age-related slow-down in muscle-protein synthesis. Synthesis rates are 30 percent lower in seniors compared to young adults. Clearly, this decrease in muscle-protein synthesis leads to reductions in muscle mass. Moreover, satellite cells situated in the basal membranes of the muscle cells also decrease in number with age. This is important because those helper cells are essential for the growth and regeneration of new skeletal muscle tissue. In other words, their scarcity may help to explain diminished muscle mass. More bluntly, this also points to the requirement for vigilant safety care and gradual progression practices in resistance training programs for older adults. With age, the capability of muscle to regenerate after overload -- and, significantly, after injury -- decreases.

Age-related declines in the levels and concentrations of specific hormones have been linked to the development of sarcopenia. Meanwhile, compromised cardiovascular health may lead to the reduced oxygen and fuel perfusion of skeletal muscles, thus promoting sarcopenia. Fitness trainers can exert a positive impact on vascular delivery by implementing balanced exercise prescriptions that include activities designed to prevent or mitigate cardiovascular disease.

In addition, nutritional inadequacy may play a role in sarcopenia. Malnutrition appears to shrink muscle mass more drastically in elders than it does in the young. Among women ages 65-plus, approximately 25 percent are believed to follow diets deficient in protein. These circumstances suggest a useful role for health-fitness professionals in terms of providing nutrition education to their older adult clients.

A most promising -- and the most obvious -- intervention in the battle against sarcopenia is safe and effective strength training. Although sarcopenia cannot be entirely prevented by physical activity, it is present to a lesser degree in physically active seniors. Losses in muscle mass and strength correspond to losses in functional measures involving balance, gait speed, stair-climbing speed and power, and sit-to-stand activity. Impaired functional performance is a reliable predictor of impending disability requiring long-term care institutionalization. Likewise, diminished muscle strength is a sound predictor of all-cause mortality in the elderly.

The benefits of exercise training with regard to the management of sarcopenia can encompass:

  • Increased skeletal muscle mass;
  • Increased muscular strength and power;
  • Enhanced function, including improved balance with lower risk of falling and bone fracture;
  • Reduced risk and/or progression of disease;
  • Greater and prolonged personal independence; and
  • Higher quality of life.

As previously noted, it is vital that older adult strength training programs incorporate effective safety precautions. Even so, progressive muscular overload is precisely what is needed to check the development of sarcopenia. Senior fitness professionals must conduct individualized plans that establish the right balance of healthful challenge and sensible conservatism. Begin by obtaining medical clearance for older clients to participate in strength training activity. Observe an initial 8-week adjustment period using minimal resistance, to be followed by gradual progression. In other words, start low and go slow. Educate clients as to the principle of gradual progression, as well as to proper training mechanics, technique, and body alignment. Follow American Senior Fitness Association guidelines for older adult resistance training. In addition, below are some special tips for instituting a muscular strength program to effectively fight sarcopenia:

  • Conduct approximately 8 to 10 exercises that work all of the major muscle groups. Stay within approximately 10 to 15 repetitions, with the goal of producing a rating of perceived exertion of "somewhat hard" (in the 12 to 13 range on Borg's RPE scale). Begin with 1 set of each exercise, although it is acceptable eventually to progress to performing 2 or 3 sets (that is, gradually over time and only as is well tolerated). To progress, first increase repetitions to their higher range. Then increase resistance (in small increments) with an attendant reduction of repetitions.
  • A good schedule for strength training is twice per week with a recovery period of at least 48 hours between workouts. Adequate recovery time is critical in light of the protein synthesis issues discussed above. If two sessions per week are not well tolerated (or cannot be scheduled for other reasons), it may still be beneficial to complete one session per week.
  • Try to limit senior strength workout session lengths to approximately 20 to 30 minutes. Sessions lasting longer than 60 minutes can discourage long-term exercise adherence and may increase the risk of accidental injury or undue strain. For reasons explained above, steps to avoid injury and overuse must always be meticulously enacted.
  • Try to include more multi-joint than single-joint movements.
  • Stick with concentric, as opposed to eccentric, muscle work.
  • Complete thorough warm-up, cool-down, and stretching activities.
  • Follow established guidelines regarding exercise slow-down and cessation signs, as well as events requiring immediate medical attention. If any existing health condition is observed to be deteriorating, immediate medical consultation is needed because this is likely to pose an exercise contraindication.
  • When safe and practical, balance and muscle coordination can be promoted by having seniors perform some of their strength exercises in a standing position while using resistance bands or free weights such as dumbbells.
  • Omit strength training for participants with arthritis (and those with other joint or bone disorders) during periods when they are experiencing pain or inflammation.
  • Remind participants never to hold their breath during strength training.
  • Teach participants to work with controlled joint movements (which includes working at an appropriate speed of movement).
  • Teach participants to work within their own personal "pain-free" range of motion.
  • After an interruption in a participant's training regimen, resume strength training at an intensity level approximately half (or less) that of the previous load.

Sources

Morgenthal, AP and Shephard, RJ. (2005). Physiological aspects of aging. In Jones, CJ and Rose, DJ, (Eds.), Physical activity instruction of older adults. Champaign IL: Human Kinetics.
Taylor, AW and Johnson, MJ. (2008). Physiology of exercise and healthy aging. Champaign IL: Human Kinetics.
Vella, C and Kravitz, L. Sarcopenia: The mystery of muscle loss. http://www.unm.edu/~lkravitz/Article%20folder/sarcopenia.html. July 30, 2008.
Welch, GL. (2005). Screening and fitness assessment. In Bryant, CX and Green, DJ (Eds.), Exercise for older adults: ACE's guide for fitness professionals (2nd ed.). San Diego: American Council on Exercise.
Zacker, RJ. (2006). Health-related implications and management of sarcopenia. Journal of the American Academy of Physicians Assistants,19(10): 24-29.

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