Friday, February 17, 2012

Age and Peak Athletic Performance

Sarcopenia - age-related muscle loss - becomes more common
and more severe after age 60, but even for 80 year olds a supervised
program of resistance exercise can add strength and improve quality of life

Peak athletic performance is reached at age 30, with remarkably little decline for the next ten years. After 40 there is a slow, steady decline to age 60, accelerating thereafter. The mid-life decline is a consequence of less oxygen being delivered to muscles; the late-life decline to a complex web of less oxygen delivery plus loss of muscle mass, compounded by disuse, obesity and osteoarthritis. But there is hope.

At the direct physiological level, theories span loss of function of nerves that control muscle movement, less oxygen uptake in the lungs, decreased oxygen delivery by blood, lessened availability of fuel, and poorer fuel use efficiency. While lung function can decline with age, especially in smokers or people with occupational exposure to airborne chemicals, the main cause is ever-decreasing oxygen delivery. With age there is a decline in maximum heart rate (roughly estimated as 220 minus age), less blood volume per heartbeat and progressive loss of capillaries delivering oxygenated blood to muscle cells. 

Fuel availability and usage are not part of the problem - muscle cells have adequate access to fuel and do not require more calories to contract. This aspect, known as "exercise economy," is assessed by looking at the metabolic calorie cost of sustained submaximal exercise.

Other changes factor into sarcopenia. Beyond 60 years, sensitivity is lessened to the signals which in younger people will trigger muscle enlargement, for example, vigorous exercise or consumption of a high protein diet.

Indirect contributors to the age decline include disuse, obesity and osteoarthritis. After college age, few people have physical labor jobs or sufficient leisure time for the 20 to 30 hours of training per week needed to maintain a level of physical activity necessary for peak performance. Recovery from sports injuries take longer. Body fat, especially torso fat, is pre-inflammatory, contributing to muscle cell insulin resistance; without this anabolic signal being received, muscles shrink. Osteoarthritis has a chicken-or-egg-first relationship with fitness, as exercise slows the progression of osteoarthritis, but this disease is a major reason people stop being physically active.

Certain sports appear to contradict the "peak at 30" hypothesis, but on closer examination, may not. For many years women's swimming and tennis were dominated by teenagers. These individual-effort sports channeled young girls into early commitment and intense training. The typical result was an early-age peak followed by mental burn-out and/or career-ending physical injury. With wider access to competitive sports via Title IX, a broader pool of women athletes across a wider range of sports finds peak ability reached in close to 30 years, just like men. In the New York City marathon, women in their mid-40s are competitively close to women ten and twenty years younger.

The net result of the direct and indirect consequences of aging? For healthy, well-trained endurance athletes there is a 20 to 25% decline in performance from age 40 to age 65. Evidence comes from bicycling time trials, and 5K and 10K runs. Decline over time is faster for occasional athletes and the sedentary.

There is hope. For the approximately ten million U.S. adults who have sarcopenia, i.e., age-related muscle loss, a supervised program of resistance exercise can partially reverse muscle weakness and improve quality of life, even when started late in life. Vitamin D at 1,000 IU/day (many elderly are vitamin D deficient) has been proven to reduce the risk of injury from falls by 20 percent. Flavonoids, chemical compounds found in foods such as red wine, dark chocolate, green tea, nuts, and some types of dark-colored fruits, and are thought to contribute to artery health.

"Article Directory by Category" lists eight other health-related topics, such as recovering from donating blood (March 2011).

3 comments:

  1. I wonder if advance maintenance can extend an athlete's peak life. Like if he often gets massage therapy in oakville to keep his muscles tip-top.

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  2. Testing that theory has problems.

    Informally, the bias of positive results means that athletes who successfully compete later in life than average will attribute their success to whatever they are doing (massage, supplements, warming up, stretching...) while we will not hear from those who did the same things and still saw their skills fade away.

    For supplements it would be possible to design a controlled experiment, but for treatments such as massage or acupuncture it is difficult to design a test that excludes the placebo effect.

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