The final rung of aerobic conditioning is an overall improve-ment in fitness and endurance. To arrive at a peak level of cardiorespiratory fitness, training intensity should remain between 50 and 80 per cent of your aerobic capacity. Gradually, you should aim to increase your training to one hour, five days a week. This should include higher-intensity exercise-activities that burn more than 6 METs (meta-bolic equivalents; see WDDTY vol 18 no 4), or any activity that uses upmore than 7 kcal/min-that leaves you short of breath. Alternating be-tween high-impact (running, tennis, dance) and low-impact (cycling, swimming, rowing) exercise offers a variety of movement and protects against injury.
Interval training, or alternating between high-intensity and low-intensity activities, can be used to increase maximum oxygen intake and improve endurance performance. In one study, a four-week high-intensity interval-training prog-ramme increased the peak sustained power output and fatigue resistance of eight competitive cyclists, improving their 40-km time-trial performances (Med Sci Sports Exerc, 1996; 28: 1427-34).
To be able to do an hour a day of exercise, however, you have to slowly work up to it. This requires a commitment above and beyond the recommendation of 30 minutes every day of moderate exercise that you hear from both the UK and US governments. Mostly, it means a commitment to keep moving, whenever you can.
Besides preventing diabetes, cancer, coronary heart disease and stroke, musculoskeletal health, of course, will also benefit from regular, intense physical activity. The strength of your bones and joints-and the risk of developing musculo-skeletal problems such as osteo-porosis and osteoarthritis-will all depend on the levels of physical activity during the critical developing years. Sustaining physical activity in young children until they reach their mid-20s will maximize peak bone mass (J Bone Miner Res, 1994; 9: 1089-96).
Nevertheless, for adults-and even for women after the menopause-regular exercise will slow down the rate of bone loss and may even lead to bone gain (J Gerontol A Biol Sci Med Sci, 2000; 55: M489-91).
Physical activity has also been shown to be beneficial in alleviating the symptoms of various mental illnesses, and is particularly successful in treating depression. Substantial research has found exercise to be as effective in helping clinically depressed people as psychotherapy and drugs (J Sport Exerc Psychol, 1998; 20: 339-57, Arch Intern Med, 1999; 159: 2349-56).
Being physically active doesn't have to take place only in the gym. Several energetic bouts of housework or gardening could confer the same benefits as an aerobics class or a circuit-training session.
This was clearly demonstrated in two large randomized trials that compared the effects of a lifestyle-activity programme with those of structured aerobic exercise on weight loss and fitness levels. The lifestyle group was encouraged to introduce activity into their daily routine (mall-walking was one example) so as to accumulate a total of 30 minutes of moderate-intensity activity every day, for most days of the week. The other group of study participants followed a traditional exercise programme that included, for example, three step aerobic classes each week.
The results from both studies were in agreement, and concluded that both the lifestyle and structured activities produced significant and comparable benefits in terms of physical fitness, and cholesterol, mean body fat and blood pressure levels (JAMA, 1999; 28: 327-334; 335-340).
So, the main objective is to keep moving in a way that leaves you slightly out of breath for at least an hour every day.
Kim Wallace and Tina Tan
- Walk or cycle to work instead of driving
- If you have to drive, park your car further away from your destination and walk the remaining distance
- If you use public transport, jog or walk briskly to the station or bus stop
- Get off the bus or train a few stops earlier and walk the rest of the way
- Take the stairs instead of the lift or escalator
- Carry your shopping around in a basket instead of pushing it in a trolley
- Engage in more active pastimes such as dancing, swimming and rambling
- Mow your lawn with a push lawnmower rather than an electric one
- Wash your car by hand rather than running it through an automatic carwash.