Importance of Resistance Training
Men and women who do not perform regular resistance exercise experience progressive muscle atrophy throughout the aging process. Research indicates that inactive adults lose about one-half pound of muscle per year during their 30's and 40's (5, 8). The rate of muscle loss may double to one-pound per year in people past 50 years of age (13). Unfortunately, the higher rate of fat gain masks the muscle loss. Adults typically lose about 5 pounds of muscle and add about 15 pounds of fat each decade during the midlife years.
Based on bodyweight the average adult changes approximately 10 pounds per decade, but based on body composition the average adult changes approximately 20 pounds per decade (5 pounds less muscle and 15 pounds more fat). A woman in her 50's may have 15 pounds less muscle and 45 pounds more fat than she had in her 20's. This represents an unhealthy 60-pound change in her body composition, which increases her risk for a variety of devastating degenerative problems such as cardiovascular disease, many types of cancer, type II diabetes, and low back pain.
While the focus is typically on fat loss (one out of two American adults is presently on a weight reduction diet plan), more emphasis should be placed on muscle gain. This is due to the fact that the 5-pound per decade loss of muscle is largely responsible for up to a 5 percent per decade reduction in resting metabolic rate (5, 12). A slower resting metabolism means that some calories previously used by high-energy muscle tissue are no longer needed, and are therefore stored as fat. Because a pound of muscle requires between 35 to 50 calories a day for tissue maintenance, a 10-pound muscle loss may reduce resting metabolism by 350 to 500 calories daily (4, 14). Think of cutting your daily food intake by 20 to 25 percent, and you will better appreciate the importance of muscle and metabolism.
Although eating fewer calories can prevent weight gain, it cannot reduce the rate of muscle loss or metabolic slowdown. It is obviously more desirable to maintain both muscle and metabolism, as well as the functional capacity to perform physical activities. Progressive resistance exercise can build muscle tissue that facilitates physical performance and enhances energy utilization throughout the senior years. In fact, strength training is the only type of exercise that can maintain muscle and metabolism as we age, and should therefore be the essential component of every senior fitness program.
Fortunately, older adults can rather quickly rebuild muscles that have atrophied from years of sedentary living. Research has repeatedly shown significant increases in muscle mass 3, 7, 9, 10, 13, 18) and resting metabolic rate (4, 15) in seniors who do regular resistance exercise. Senior research subjects at Tufts University (4) and the University of Maryland (15) added 3.0 to 3.5 pounds of muscle and increased their resting metabolism by 6.8 to 7.7 percent after 3 to 4 months of standard strength training.
We recently conducted a large-scale strength training study with 1,132 men and women between 20 and 80 years of age (18). The younger adults (21-40 years), middle-aged adults (41-60 years) and older adults 61-80 years) made similar improvements in bodyweight, percent fat, fat weight and lean (muscle) weight after 8 weeks of basic resistance exercise.