I have noted elsewhere that the average male between 18-35 years has 40-44% muscle. This drops to 32-35% for the 56-75 year cohort. A 170-pound average 20-something male will, on average, lose 13.6 pounds of muscle by the time he’s 60 (1). Sarcopenia, often defined as the age-related decrease in lean body mass, is not well known by the public. I speculate that this is because Big Pharma has not developed a pill for it, and there are no trendy alt-medical approaches to gaining muscle. Astonishingly, its direct costs approached $18.5 billion in the United States instead of $16.3 billion for osteoporotic fractures. Of course, Pharma has a pill for osteoporosis. Sarcopenia is so endemic that most Americans think it is inevitable with age and irreversible. This is entirely incorrect.
“Sports Health” published an interesting paper by a group of Duke University doctors in 2014, “Muscle Changing in Aging, Understanding Sarcopenia“. It is an informative survey paper on the prevalence, medical characteristics, and management of sarcopenia with interesting facts that defy the shared wisdom of the American public.
The loss of muscle fiber with age is not uniform. Human muscle tissue is made of various types of fiber, roughly categorized as Type I and Type II. The former is smaller, slow-contracting aerobic fibers that contract weakly but have significant endurance. These are the predominant muscles used in running long distances. On the other hand, Type II fibers are large, contract forcefully, and tire quickly. These are the muscles sprinters use or when weight lifters do a set of repetitions. They produce large amounts of force and tire within tens of seconds. Aging tends to bring about the loss of a greater proportion of Type II fibers, resulting in smaller muscles in weaker individuals. In runners, sprinting speed tends to decline more quickly than the ability to run long distances. This results in the characteristic frailty so often seen in older adults. They are weak. The endemic inactivity of the general population results in loss of muscle. This leads to increasing weakness, which contributes to even greater inactivity.
The abysmal fitness of seniors is so prevalent that culture thinks that it is normal. Yet inactive seniors respond to appropriate training proportionally as much as younger people. Untrained adults between 60 and 80 can increase their aerobic fitness with training, with improvements arising from their central cardiovascular system and muscular adaptation. For men over 66, training at 80% repetition maximum for 12 weeks can improve their strength by 5% per day, an improvement similar to far younger men. At 90, strength can be improved by 175%, and the cross-sectional area of the thigh can be increased by 15%. This leads to the conclusion that “cardiovascular health is greatly improved with increased activity, and alternately, increased fragility and mortality is associated with less physical activity. For many patients, the age-related effects on skeletal muscle are largely reversible.”
All this is not to deny that other factors are involved with fitness loss and increasing morbidity in seniors. Diet changes for many reasons, including physiological, psychological, and social. These changes often result in reduced protein intake, Vitamin D, and long-chain polyunsaturated fatty acids (Omega-3 and Omega-6 fatty acids), all linked to decreased muscle function. Likewise, beginning around the age of 35, testosterone levels decrease by 1% to 3% per year in men and women who become menopausal. These hormonal changes lead to reduced muscle mass and increasingly fragile bones. Replacement therapies are fraught with side effects.
Despite unavoidable metabolic changes noted here and in other posts on this site, what commonly passes for old age is more the result of unhealthy cultural acceptance of inactivity and encroaching poor diet. These are largely reversible. Ultimately, the best we can strive for is the maximal compression of morbidity (2).