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How can exercise training benefit older adults?

This is an excerpt from Practical Guide to Exercise Physiology-2nd Edition by Robert Murray & W. Larry Kenney.

Older women and men respond to training similarly to younger people, increasing performance capacity along with physiological and metabolic function. For that reason, it is not unusual for 60-year-old athletes to have performance capacities that are greater than the capacities in people half their age. The ability to maintain impressive performance capacities occurs despite the fact that maximum cardiac output declines with age because both maximum heart rate and maximum stroke volume fall with age, as does blood flow to the arms and legs.

One of the challenges in establishing the effects of aging on physical fitness and performance is that it is difficult for scientists to separate the effects of aging from the effects of decades of relative inactivity in sedentary individuals. The same complication is true with older adults who have remained active but have reduced training intensity and duration over the years. Regardless, the good news is that proper training clearly improves all facets of physical capacity, including muscle mass, strength, endurance, aerobic capacity, agility, balance, coordination, flexibility, and anaerobic capacity.

After age 60, the failure rate for opening the lid on a jar rises substantially. Loss of strength and muscle mass are due to decreased anabolic signaling, increased muscle catabolism, reduced physical activity, and inadequate protein intake.

The Strong Live Long

After age 40, sedentary individuals lose an average of 1% of their muscle mass each year (a range of 0.5-1.2% per year) along with a loss in strength that averages 3% per year. This loss of muscle mass is not unusual; all mammals experience something similar as they age. But when the loss of muscle mass and strength become so severe that muscular weakness interferes with the activities of daily living, there is a substantial negative impact on health care, living conditions, illnesses, and injuries. The severe loss of muscle mass and functional strength associated with aging and a sedentary lifestyle is called sarcopenia, a word coined in 1988 that means “poverty of flesh” in Greek. Sarcopenia occurs as a result of the loss of motoneurons and their associated motor units, combined with an increase in muscle protein breakdown and a decrease in muscle protein synthesis, leading to gradual decline in muscle mass and strength.

Performance Nutrition Spotlight

In addition to helping support muscle strength and mass in older adults, diets higher in protein (e.g., 1 g of protein per lb of body weight per day [0.5 g per kg BW per day]) are associated with greater weight loss, more fat loss, and better protection of lean body mass.

Protein synthesis in the muscle cells in older adults is less sensitive to dietary protein intake and to the normal stimulation of exercise. This anabolic resistance is one characteristic of aging muscle that predisposes many older adults to sarcopenia. Dynapenia is the term that refers to inordinate muscular weakness. Fortunately, regular training and physical activity in general can substantially reduce the rate at which muscle mass, strength, and neuromuscular function are lost, even in very old adults (e.g., >90 years of age).

Figure 12.2 shows a striking example of the effect of strength training on muscle mass in later middle age. Strength training can also slow the loss of type II muscle fibers, and physical activity that incorporates weight-bearing exercises such as running and jumping (impact exercise) helps slow bone loss. Reducing the loss of muscular strength, muscle mass, and bone mass during aging is critical in maintaining the ability to live independently, decreasing the incidence of accidental falls, promoting more rapid recovery from injury and illness, and improving the overall quality of life.

Performance Nutrition Spotlight

After retirement, many older adults move to warmer climates where staying well hydrated can be challenging. Being even slightly dehydrated day after day can impair cognitive function and increase the risk of chronic kidney disease.

With age, the normal close relationship between muscle mass and muscle strength is altered. Many older adults lose substantial muscle mass as they age, but if properly trained, can maintain sufficient muscle strength to preserve functional capacity and independence. It is also important that older adults maintain muscle endurance because leg muscles that fatigue quickly increase the risk of falling. Along the same lines, training that improves muscular power and the rate of force production not only reduces the risk of falls but helps older adults effortlessly rise from chairs, climb stairs, and improve their walking speed. Improved strength in older adults can result from positive changes in muscle mass and, perhaps more important, adaptations in the nervous system.

Proper strength training improves an older adult’s ability to voluntarily recruit and activate the appropriate muscles, deactivate the appropriate antagonistic muscles, and better synchronize synergistic muscles. Improvements in muscle strength, endurance, and power in older adults prolong the ability to live independently, accomplish activities of daily living, recover more quickly from illness and injury, and reduce the risk of falls.

Falls in older adults can have catastrophic consequences whenever fall-related injuries result in even temporary immobility. The “catabolic crisis” that can follow fall-related injuries and immobility often sparks a rapid onset of sarcopenia and subsequent frailty, increasing the risk of an early death. Regular physical activity—including strength training—reduces fall risk in older adults by 30% to 40%, along with a 40% to 65% reduction in the risk of severe injuries from falling. In addition to at least two sessions of strength training each week, older adults should engage in multicomponent physical activities such as yoga, tai chi, team sports, dancing, handball, tennis, and pickleball—activities that develop stamina, strength, flexibility, balance, agility, and coordination. Such activities are better than strength training alone at improving overall functional performance in older adults.

Endurance training has little impact on the loss of muscle mass with age. Only strength training preserves muscle mass with age. However, endurance training does help slow the decline in V.O_2max with age (figure 12.3). Older adults who begin aerobic exercise training usually experience the same 10% to 20% increase in V.O_2max as younger individuals. Because maximal heart rate declines with increasing age and cannot be increased with training, improvements in V.O_2max occur as a result of increases in stroke volume and a-V.O_2diff (due to increases in oxidative enzyme activity in muscle cells).

Being physically fit also lowers the risk of heart attack (myocardial infarction) and improves the outcome when a heart attack does occur. Immediately following a heart attack, ischemia-reperfusion injury to cardiac muscle cells (and cells in other tissues that may have been temporarily deprived of oxygen) can occur as damaged, oxygen-starved cells are suddenly exposed to a higher blood oxygen content, resulting in inflammation and oxidative damage. Regular physical activity reduces the death of cardiac muscle cells following a heart attack and lowers the incidence of potentially dangerous heart arrhythmias. Aerobic training and HIIT are superior to strength training alone at increasing the number of blood vessels, improving the function of those vessels, and providing antioxidant protection for cardiac cells.

Physical activity helps keep mitochondria young. In addition, some of the myokines released from active muscles appear to promote neurogenesis in the brain and improve memory.

More Excerpts From Practical Guide to Exercise Physiology 2nd Edition

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