Age-related muscle changes

One of the hallmarks of aging is the loss of muscle mass and strength. Much of this loss can be explained by changes in the neuromuscular system such as decreases in the number of motor neurons, the number of muscle fibers, and the size of muscle fibers. But it's important to ask whether these changes are a consequence of aging or simply the result of an inactive lifestyle.


Keywords :
muscle, bodybuilding, strength, aging, muscle loss, loss of strength, lifestyle, bodybuilding, physical exercise


One of the hallmarks of aging is the loss of muscle mass and strength. Much of this loss can be explained by changes in the neuromuscular system such as decreases in the number of motor neurons, the number of muscle fibers, and the size of muscle fibers. But it's important to ask whether these changes are a consequence of aging or simply the result of an inactive lifestyle.

Age-related muscle changes

Age-related decline in muscle mass appears to occur in two phases. The first, so-called "slow", phase of muscle loss, during which 10% of muscle mass is lost, occurs between the ages of 25 and 50. The majority of muscle loss occurs after that, with an additional 40% lost between the ages of 50 and 85. Overall, the human body loses 50% of its muscle mass by the age of 80. This muscle atrophy is explained by a significant decrease in the total number of muscle fibers and their size.

Aging has been shown to result in a loss of fast-twitch fibers producing power and speed (especially IIb) and an increase in slow-twitch, more aerobic fibers. This seems logical since movements that require high contraction speed (like jumping and sprinting) tend to be less common in older adults.

Mechanisms of loss of strength

Problems with decreased strength manifest in its contribution to osteoporotic decline in bone density, arthritic joint pain, and overall reduction in functional capacity.

The loss of muscle mass is obviously accompanied by a decrease in muscle strength. However, as with muscle loss, most strength losses are not significant until the sixth decade. As briefly mentioned, this loss of strength can be attributed to a decreased number of motor units (nerve-muscle fiber complex), decreased number of muscle fibers, and reduced muscle fiber size. It is also known that a decline in leg strength precedes loss of upper extremity strength in older adults. This point is important because strength, rather than cardiovascular function, is considered the most physically limiting factor in older adults. This is evident when considering the strength-limiting activities that many older adults face, such as getting up from a seated position or climbing stairs.

Encouragingly, aging does not appear to affect eccentric strength. This phase of contraction is an important consideration for older adults because of the possible link between low eccentric force and the incidence of falls in older adults.

The importance of an active life

Regular exercise is the most effective way to slow and counter the effects of age-related loss of muscle and strength. Comparisons between active and sedentary older adults suggest that much of the strength loss associated with aging is due to lifestyle factors. For example, people who continue to use certain muscles on a regular basis do not experience the same age-related declines in strength. In general, muscle atrophy, and therefore loss of strength, occurs whenever muscles fail to work against a given load. This results in a decrease in protein synthesis accompanied by an increase in protein degradation. Overall, the muscle atrophies and loses much of its strength, characteristics commonly seen in astronauts during spaceflight. Incorporating regular resistance training is the most effective way to mitigate this effect.


Encouraging results

Studies have consistently shown that regular exercise can improve muscle endurance and strength in older adults in a manner similar to that seen in younger people. One of the largest studies in this area was carried out at McMaster University several years ago. Researchers examined the effects of two years of twice-weekly strength training (80-85% 1RM) on 114 subjects aged 60 to 80 years old. The results indicated a steady increase in strength in each of the muscle groups tested, with no signs of plateauing. Strength gains were also accompanied by significant increases in muscle mass and, perhaps more importantly, these strength gains were shown to translate into improved function (measured by walking and climbing the stairs).

Although some inevitable changes occur with aging, it is possible to delay or mitigate the losses in muscle mass and strength that normally accompany these changes. Since many activities of daily living, such as walking, climbing stairs, and getting up from a chair, rely on strength, it is imperative to minimize age-related loss of strength as much as possible. The muscles of older adults retain their capacity to adapt; therefore, regular resistance training (2-3 times per week) should be incorporated into the lifestyle of these individuals. Additionally, a similar strength training protocol should be used in young adults as a means of prevention and to stay healthy into their golden years!