Positive Health Online

The lack of physical activity is one of the less desirable consequences of our transport system. The dominance of the motor vehicle is not the only cause of our increasing lack of physical activity. Office jobs and passive leisure activities such as watching TV and movies also contribute to a sedentary lifestyle. But transport plays a major role in creating an inactive population. The consequences for health are disastrous. Not only does a sedentary lifestyle reduce fitness and well-being, but it increases the risk of many chronic diseases, including heart disease, high blood pressure, osteoporosis, diabetes, cancer, anxiety, depression and life expectancy (Pate et al 1995).

Most people know that physical activity is good for their health but many don't know how much activity is needed to bring about the benefits. And few are as active as they should be. Less than 30% of English people over the age of 16 are physically active at the frequency and regularity required. For young women, only 10% are sufficiently active to reap the benefits. These are the depressing results of two surveys done in 1990 and 1991 of a representative sample of more than 7,000 people throughout England (Walker & Hoinville 1995). The conclusion was that most people over-estimate the amount of physical activity in their lives and underestimate the amount of physical activity they need to do in order to achieve benefits to their health.

Health benefits can be achieved by 30 minutes of moderate-intensity physical activity every day (Pate et al 1995). The 30 minutes can be made up of short bouts of activity throughout the day. They do not have to be taken in one continuous burst of activity. Nor do they have to be taken in a vigorous exercise programmes in a gym. Cycling and walking are types of transport that can contribute to the amount of physical activity taken. Health benefits will be achieved by regularly cycling at up to 10 mph and walking briskly at a rate of 3-4 mph for two or more miles. Other daily activities that count as moderate intensity activities are heavy cleaning in the home, digging the garden, mowing the lawn with a power mower, heavy DIY such as mixing cement or painting, swimming with moderate effort, table tennis and football. The amount of activity is important. There are greater health benefits from spending half an hour a day in moderate activity than 10 minutes a day in vigorous activity.

The benefits of physical activity on the cardiovascular system are well known. In this column, I'd like to focus on osteoporosis.

Osteoporosis is the cause of most of the bone fractures suffered by older people, particularly older women. By the age of 60, a quarter of women in Britain are affected by osteoporosis. By the age of 70, half are affected. As a result of osteoporosis, there are some 180,000 hip fractures each year. By the age of 90, a quarter of women can expect to have a hip fracture (DOH 1995).

The risk of a hip fracture can be reduced to half by regular physical activity. But the type of activity is as important as the amount and regularity. In order to prevent osteoporosis and fractures, the activity should be of the weight bearing kind. That means, walking instead of swimming. The best prevention is to start early in life, preferably before puberty, and to maintain it throughout life. Those who stay physically active have less chance of falling, are able to sustain their balance and mobility into old age and remain independent for longer than those who are sedentary (DOH 1995).

Most women are not active enough to reduce their risk of osteoporosis. Both men and women become less active as they age. But even younger women are not as active as they should be (Walker & Hoinville 1995). It is possible for elderly and middle aged women to slow down the rate of bone loss and even to increase bone mass as a result of increasing their physical activity (Smith et al 1986). But the real benefits from physical activity in terms of osteoporosis come from a lifetime of physical activity.

The effects of past and recent physical activity on the risk of hip fractures was examined in a Canadian study (Jaglal et al, 1993). The activity levels of more than 380 postmenopausal women who had had a hip fracture were compared with that of more than 1100 older women who had not had a hip fracture. To estimate past activity levels, they asked the women how active they were when they were 16, 30 and 50 years old. To estimate recent activity, they asked about activity in the past year or in the year before the hip fracture. The researchers took account of all the other important factors which influence the risk of fractures such as smoking, amount of calcium in the diet, use of Hormone Replacement Therapy, etc. They found that past physical activity, whether moderate or intense, had a significant protective effect. In other words, women who had been active when they were younger were only half as likely to have a hip fracture than women who had not been active. Recent activity also protected against fractures as long as it was moderate. But for some reason, women who had been very active in the recent past were not protected from hip fracture.

Next month, I will explore the benefits of physical activity on cancer risk.

References:

DOH 1995, Health of the Nation Physical Activity Task Force, Proposals for comprehensive physical activity strategy for England, Consultation Paper, Department of Health, London.

Walker & Hoinville, 1995, Physical Activity Matters Across England, Health Education Authority, London.

Jaglal et al. 1993, Past and recent physical activity and risk of hip fracture, Am J Epidemiol, 138:2, 107-18.

Pate et al, 1995, Physical Activity and Public Health – recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine, 273,5, p402-407.

Smith & Raab, 1986, Osteoporosis and physical activity, Acta Meal Scand Suppl, 711, p149-56.