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Regular exercise is essential for maintaining muscle tone and putting stress on bones – necessary not only for halting bone loss but stimulating the formation of new stronger bone tissues.
Astronauts in space flights lost considerable amounts of bone tissue, at a rate of 0.5 per cent per month, after a short time in a weightless state. More recent missions have included exercise to try to prevent bone depletion; unfortunately, this exercise has proved ineffective without the stress and pull of gravity on bone and muscle.
Similar problems occur in hospital patients or those confined to wheelchairs – a condition called disuse osteoporosis. Bones weaken and shrink when not used, in a sedentary lifestyle, just as muscles do; bones respond by becoming stronger and larger when stress is placed on them with exercise. Exercise increases blood flow to bones, bringing in nutrients for new formation. Exercise can change the levels of the body’s hormones that form bones, creating a better environment for new bone formation, increasing oestrogen and decreasing harmful adrenal hormones. When athletes build up muscles, the strenuous training also builds bone mass.
A study has been carried out at the University of North Carolina, Chapel Hill, USA, under the direction of orthopaedist Peter Jacobson: 400 sedentary women aged between thirty-five and sixty-five were compared with 80 women of the same age range who played tennis regularly each week. Of those under fifty-five, there were no special differences in bone structure. But women over fifty-five in the study had much stronger bones among the tennis-playing group. Research suggests that tennis, jogging and other ‘weight-bearing’ exercises may help to strengthen older bones.
Other studies of menopausal women have them square dancing, jazz dancing and performing isometrics to determine the changes in their bone mass. Bone loss may not be inevitable in later years, but proportional to a slowdown in exercise and physical activities.
Although many people think of themselves as being fairly active, very often their hectic lives mean they are mentally and socially active but not physically. Exercise is a Do-It-Yourself venture; no one else can do it for you. Make it a part of your lifestyle for the rest of your life!
At the same time you’ve got to strike the right balance: if you exercise as vigorously as some athletes that you stop menstruating, you can place yourself in danger of having bone loss as a result of lower oestrogen levels. Loss of menstruation, called amenorrhoea, occurs in up to 50 per cent of competitive runners and ballet dancers but affects only 3 to 5 per cent of women in general. If a woman does not menstruate for a year, she should have her bone density checked.
In recent research, Robert Marcus, M.D., of Stanford University School of Medicine, Christopher E. Cann, Ph.D., of University of California, San Francisco, and others, studied bone-mass variations in a group of white long-distance runners (running up to 160 kilometres a week). Of the seventeen women, six had regular menstrual periods and eleven had none. Four of the women without periods had started intense training before the onset of menses. The non-menstruating athletes had 17 per cent lower spine density than the menstruating women. Cortical bone mass was not apparently affected by lack of menstruation, but trabecular bone density was lower. The study supported the idea that intense physical training at an early age may delay menarche, and women would be better not to train to such an extent that they don’t menstruate regularly.
Although athletes may be under pressure from coaches and peers to keep weight down, they still need to consume sufficient calories, calcium and protein, and avoid vitamin overdoses. Most importantly, non-menstruating athletes may need a greater intake of calcium daily, similar to postmenopausal women.
Women should not be frightened off exercise, however, as few have such tough multi-mile running programmes, as in the previously mentioned study, or do other aerobics so strenuously. The effect of regular exercise on bone density is positive, providing calcium intake is maintained; the benefits of exercise still far outweigh the hazards.
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