Muscle power and strength
Between the ages of 65 and 90, muscle power is lost more rapidly than strength – 3.5% per year for the former compared with about 1.8% for the latter. Also, concentric force development is lost more rapidly than the eccentric variety. In both sexes there is little fall-off in strength until about the mid-40s, after which it drops by approximately 25% by age 65. In women, there may be an accelerated post-menopausal fall-off in power and strength. With ageing in general there is progressive muscle atrophy (wasting).
Nevertheless, to some extent these force parameter losses appear to be reversible ; for example, eight weeks’ strength training in 56-70- year-old-men has produced marked improvement in local muscle endurance ; and strength training, even of nonagenarians, may produce a doubling of force development by quadriceps.
It is noteworthy that regular exercise appears to be accompanied by a slowing in the rate of decline of movement/reaction times in the elderly, which could help minimise falls or stumbling during the later stages of endurance runs or races. Studies have shown that ‘old
active’ subjects have faster response times than both their inactive counterparts and ‘young nonactive’ people.
Well-used tendon retains more of its elastic properties. And collagen turnover is increased with exercise, which would allow for greater elastic energy storage in tendon and ligament, thus improving running economy. Regular weight-bearing exercise has been shown to decrease the rate of bone demineralisation leading to osteoporosis, although this effect is reasonably specific to the body segments exercised.
In sedentary people, thermal control in the cold is diminished with age on account of a combination of factors, including reduced body mass, lowered basal metabolic rate and diminished shiver response by muscles. But exercise has also been shown to improve thermal
control, helping older people to resist hypothermia in the cold and overheating while exercising in hot weather.
There is increasing evidence that moderate exercise, perhaps particularly in the elderly, may enhance some immune responses and lead to a lowered incidence of illness – eg respiratory disease. In very approximate terms, one might estimate that 20-40% (or more) of the
physiological deterioration associated with ageing is not inevitable but is due to a detraining effect of decreased exercise, often coupled with an increase in body fat. The athletes’ motto ‘If you don’t use it – you lose it’ applies equally to the ageing population. And the extraordinary
marathon performances of elderly runners set out in the table on the previous page confirm it.