In the well-known Harvard Alumni Study, which examined mortality rates over a 22- to 26-year period in more than 17,000 men who had attended Harvard University, life expectancy was about two years longer for those who expended 2,000 calories per week during exercise, compared to individuals who were sedentary.
Since 2,000 weekly calories can be consumed during just 15 miles of jogging, it's clear that a fairly modest investment in exercise can bring a large return.
Within limits, exercise's protective effects tend to expand as you increase your quantity of exercise. Jogging just 10 miles per week improves your chances of living longer rather dramatically, compared to completing no exercise at all. Covering 25 to 30 miles each week lowers your risk of dying even more. Beyond 30 miles, though, there's little evidence that more miles limit the grim reaper's activities any further.
Ralph Paffenbarger, M.D., one of principal investigators in the Harvard Alumni Study, summarises the benefits of exercise with a neat formula: For each hour that a person exercises, he/she gets roughly two extra hours of life! Paffenbarger's proposition is true only for reasonable amounts of exercise, though (probably for up to 30 weekly miles of running). Otherwise, immortality could be 'purchased' simply by exercising for slightly more than 12 hours each day, which would 'buy back' the lost 24-hour period.
How it works
Why does exercise help us live longer? Blood levels of high-density lipoprotein cholesterol (HDL-C) are inversely related to the risk of developing coronary heart disease (the higher the HDL-C, the lower the risk), and exercise raises HDL-C. Running just nine miles per week hikes HDL-C by 8 per cent. Running 17 weekly miles shoots HDL-C up by 12 per cent. Ambling 31 miles per week heightens HDL-C by 19 per cent. Individuals who jog just 11 to 14 miles per week can lower their risk of heart attack by 30 per cent or so.
Exercise also tends to lower blood pressure, decreasing the risk of heart attack and stroke, and trims the chances of becoming obese or developing non-insulin-dependent diabetes mellitus. Regular physical activity has also been linked with lower rates of certain kinds of cancer. In general, exercise extends longevity by diminishing the risk of a variety of different ailments.
Source: PEAK PERFORMANCE ONLINE - www.pponline.co.uk
