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Resistance training and the older adult - continuing education, includes quiz for two units

American Fitness, Sept-Oct, 1997 by Deborah Riebe

The population of the United States is getting older. The fastest growing segment of the population consists of those over 65, and the fastest growing subsegment is over 85. In fact, for the first time in history, the number of Americans over the age of 65 surpasses the teenage population.

It is crucial to get the message out to older adults that physical activity is an important component of healthy living. The average life expectancy is approaching 80, and to remain functionally independent, older individuals must be able to complete the activities of daily living. Simple tasks that many of us take granted, such as carrying groceries, climbing stairs, getting in and out of the bathtub or even rising from a chair require a certain degree of strength. The loss of strength that accompanies aging and inactivity can cause an older person to be dependent on others for care and may result in a decline in quality of life.

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With this in mind, not only should older adults be physically active, they should include a strength training component in their overall exercise plan. The 1990 American College of Sports Medicine's (ACSM) position statement suggests all healthy adults should participate in strength training. The ACSM recommends a minimum of eight to 10 exercises involving the major muscle groups be performed at least two times per week. A minimum of one set of eight to 12 repetitions should be completed for each exercise.

Changes In Strength With Aging

The highest strength levels for men and women are usually reached between the ages of 20 and 30. Thereafter, strength in most muscle groups declines steadily. The decline progresses slowly at first, and then more rapidly after middle age. By age 65, a 20% decrease in strength usually occurs. This decline in strength is attributed not only to advancing age, but also to a sedentary lifestyle.

The loss of strength often makes it impossible for older adults to meet the demands of daily life. For example, a study conducted by Bengt Saltin, M.D. measure the ability of middle-aged and older adults to open the cap on a jar that had a set resistance. It was found that 92% of men and women aged 40-60 were able to open the jar. However, after age 60, the failure rate for this task increased dramatically. Only 32% of the subjects between 71-80 years were able to successfully open the jar.

Resistance training does not prevent the loss of strength that accompanies aging, but it slows it considerably. In fact, resistance training allows an older adult to perform better at age 60 than most inactive individuals at half that age.

Physiological Changes With Aging

The age-related loss of strength results primarily from the substantial loss of muscle mass that accompanies aging and decreased physical activity. Adults usually experience a 40-50% reduction in muscle mass between 25 and 50 years of age, and a substantial increase in subcutaneous fat. Changes in the nervous system also contribute to the decline in strength that companies aging.

The decrease in mass, also referred to as muscle atrophy, is due to changes in fibers. As an individual ages, there is a decrease in the number of muscle of muscle fibers are lost per decade after age 50. The size of both fast-twitch and slow-twitch fibers also decreases with aging, especially the fast-twitch fibers in the muscles of the lower body. The decrease is offset by resistance training. In comparison to sedentary individuals, the decline in fiber size is smaller in those who are physically active.

Aging affects the nervous system's ability to process information and activate muscle. Skeletal muscles are voluntary, and contract only when a message is sent from the brain via nerves. Movements are slowed with aging, although people who remain physically active are only slightly slower than younger, active individuals.

Regular physical activity lessens aging's impact on muscular strength and endurance. Exercise can't stop biological aging, but many physiological decrements can be reduced by a physically active lifestyle. The old adage "if you don't use it, you lost it" certainly applies to muscle.

Trainability Of Older Adults

Many studies have demonstrated older adults can increase their strength and muscle mass. Walter Frontera, M.D., trained previously sedentary, healthy men between the ages of 60 and 72 for 12 weeks at 80% of their one repetition maximum. At the end of the study, knee flexion strength had increased by 107%, and knee extension strength was enhanced by 227%. These impressive improvements in strength were accompanied by a significant increase in muscle size, referred to as hypertrophy. There was a 27.6% rise in the size of fast-twitch muscle fibers, and a 33.5% increase in size of slow-twitch muscle fibers.

Another study by Wayne Campbell, Ph.D., observed men and women ages 56-80 before and after a 12-week weight training program consisting of upper-and lower-body exercises with the resistance set at 80% of the subject's one repetition maximum. Exercise sessions were held three times per week an lasted approximately 30 minutes. Following the program, the participants gained approximately three pounds of muscle, lost four pounds of fat, increased resting metabolic rate and needed to eat 370 more calories per day to maintain their body weight.

Resistance training and the older adult - continuing education, includes quiz for two units

American Fitness, Sept-Oct, 1997 by Deborah Riebe

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