Kenneth Gardner
THE AGE-RELATED changes that occur in our musculoskeletal system are causes for concern. The loss of bone and muscle strength often leads to serious life-threatening injuries. Many of the age-related changes that occur in these systems are the result of physical inactivity.
With age, bones become more fragile. Serious and often debilitating fractures are common in the elderly. With age, the loss of calcium results in a decrease in bone mass. Bone mass decreases by about 10 per cent from peak bone mass to age 65 and by 20 per cent by age 80. In women, the loss is higher, amounting to about 20 per cent by 65 and 30 per cent by age 80. Men tend to lose bone mass by about one per cent per year after the age of 50, where as women begin to lose bone mass in their early 30s with two to three per cent decline per year after menopause.
Studies have found that older women who exercise for one hour, twice weekly for eight months increased their bone mineral content by 3.5 per cent during the same period whereas the sedentary control groups of a similar age, lost 2.7 per cent during the same period. The evidence is clear, regular physical activity and resistance training appear to have beneficial effects on the rate of age-related bone loss.
IMBALANCE
Osteoporosis is characterised by decreased bone mass and increased susceptibility to fractures. After reaching its peak, bone mass declines throughout life because of the imbalance in remodelling of the bone. Remodelling is the replacement of old bone tissue with new bone tissue. Bone remodelling serves to help maintain calcium balance. Mechanical and electrical factors, hormones and local regulatory factors influence remodelling.
Osteoporosis is a major public health problem. The treatment of osteoporosis tries to prevent or retard bone mineral loss. In recent years, scientists have identified several measures that may help reduce the toll of osteoporosis. Oestrogen replacement is the only one of these measures in which there is well-documented evidence of its effectiveness in the prevention of fractures from osteoporosis. However, oestrogen replacement has its related drawbacks. Our calcium needs differ depending on age. Generally, adults age 19 to 50 should get at least 1000 mg each day to maximise peak bone mass; this is the better approach.
Weight-bearing exercises such as walking, jogging, and weight training are some of the better approaches for strengthening the bones. Swimming is a non-weight bearing exercise that has helped, but to a lesser degree. Exercise also builds muscle strength and agility which can reduce the risk of falls and fractures. The greater the physical stress and compression on a bone, the greater the rate of bone deposition which is why weight-bearing exercises are recommended.
Kenneth Gardner is an exercise physiologist at the G. C, Foster College of Physical Education; email: yourhealth@gleanerjm.com.
