34 MENOPAUSE SYMPTOMS

Regular weight-bearing exercise can boost bone density, although the force of gravity appears to be key in creating this effect (swimming, for instance, is less effective at building bone density than walking or running). Astronauts, for example, rapidly lose bone density while in zero-gravity.

Bone density will be most notable in the area most used in any given exercise. Wolman gives the example of a professional tennis player, whose playing arm can have bones as much as 30 % more dense than elsewhere in the body, while runners will show augmented bone strength in the femur (thigh bone) and spine.

Both aerobic exercise and strength training can help to augment bone density. A regular exercise regimen of either type consistently executed over an extended period can effectively be prescribed to boost bone strength. Regular, gentle exercise can even reduce osteoporosis risk in the very elderly. In addition to increasing bone density, regular exercise also helps to strengthen muscle and improve balance in older people, and thus lessens the risk of falls and fractures.

For the majority of the population, regular exercise is vital for bone health. However, female athletes who exercise strenuously are actually at a risk for weaker bones. Young or middle-aged women who are competitive athletes (or follow an unusually stringent weight-loss program involving extreme exercise) may stop menstruating, a condition called "amenorrhoea."

Amenorrhoea is typically associated with low body fat, a low-calorie diet, and intensive training. During amenorrhea, estrogen levels are insufficient, meaning that bone density will diminish. This decrease can be reversed if amenorrhoea lasts for less than six months, but reversal becomes increasingly unlikely the longer amenorrhoea continues, thus proportionately increasing the risk for osteoporosis. Athletes have been diagnosed with osteoporosis and suffered from related fractures as early as in their teens and twenties.

A female athlete who has ceased menstruating for six months or longer should see her doctor. Reduced training intensity, a higher-caloric diet, and/or use of oral contraception can help to reverse the condition and thus protect against bone loss, although the athlete may be resistant to these treatment measures.