There is little doubt that regular exercise is beneficial to the long-term health of an individual. On the other hand, excessive exercise may be detrimental, but the degree of excess must be very high to be significantly detrimental.
The intensity of an exercise activity can be measured by comparison to the resting metabolic rate (the rate at which the body uses energy when at rest) as shown in the table below.
METS = Metabolic equivalent of task (a standard measure of the energy used to complete tasks)
|Walking slowly (3km/h)||2.5||Walking moderately uphill||6|
|Walking moderately (5km/h)||3.5||Aerobics (high impact)||7|
|Rowing lightly (50 watts)||3.5||Backpacking||7|
|Golf, pulling buggy||4.5||Jogging||7|
|Mowing lawn||4.5||Tennis singles||7.5|
|Dancing rapidly||5||Cycling moderately (20km/h)||8|
|Aerobics – low impact||5||Walking up stairs steadily||8|
|Cricket – bowling or batting||5.5||Step aerobics||9|
|Tennis doubles||5.5||Running (10km/h)||10|
|Walking briskly (6.5km/h)||5.5||Swimming freestyle||10|
|Cycling, stationary (100 watts)||5.5||Cycling fast (25km/h)||10|
|METS = metabolic equivalent of task||Running fast (12km/h)||12|
A figure of 400 kilojoules (100 calories) will be used by walking briskly for 20 minutes, swimming for 10 minutes, or running flat out for 7 minutes.
The interesting corollary of these figures is that if you walk a kilometre you will use more kilojoules than if you run a kilometre because it takes more time to walk than run. Even fewer kilojoules are used if you cycle for a kilometre as much of your body weight is carried by the bike.
The general rule of “all things in moderation” should apply to exercise as much as anything else. While regular exercise is good for general health, excessive amounts can be harmful, as can be seen by the heart failure, premature arthritis, psychiatric disturbances and other chronic wear and tear injuries suffered by elite and endurance athletes (for example, fitness guru James Fixx who died from a heart attack in his fifties).
The best forms of exercise are cycling (mobile or fixed) and swimming, as the even and minimal stress exercises all muscle bundles and joints in the body. Brisk walking is the best exercise for those of more mature years.