Men who kept a high level of fitness in their midlife would then have around a third lower risk overall of dying from certain cancers after the age of 65. The benefit was in comparison with those men maintaining low cardiorespiratory fitness against treadmill tests in a study that followed nearly 14,000 men from 1971 to 2009.

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The men's treadmill tests measured fitness level by slowly stepping up speed and grade until the point they wanted to stop.

For specific types of cancer in the research published in JAMA Oncology, high cardiorespiratory fitness, compared with the least fit men, resulted in risk being lowered by:

There was, however, no benefit for prostate cancer found in the cohort study analysis produced by Dr. Susan Lakoski and colleagues at the University of Vermont, Burlington.

The paper in fact shows a higher risk of prostate cancer associated with men who kept highly fit, but the authors look to other findings that may explain this "interesting" result - men with higher cardiorespiratory fitness may also be more likely to get screened or to take part in preventive health consultations, and so may simply show higher rates of diagnosis.

For the reductions in risk for the other two types of cancer, the paper concludes that incremental increases in fitness give incremental reductions in risk.

The authors have analyzed a percentage risk reduction for every metabolic-equivalent unit of oxygen consumption - for every MET ("metabolic equivalent of task"), a measure of exercise capacity for individuals, and a factor of increased energy use per minute for their bodyweight during activity compared with resting oxygen consumption.

"Every 1-MET increase in cardiorespiratory fitness was associated with 17% and 9% relative risk reductions in lung and colorectal cancer risk, respectively," say the authors.

For those men diagnosed with a cancer in Medicare age (65 years and over), the risk of dying from it was also reduced by high midlife fitness. Such men with cancer were also considerably less likely to die from cardiovascular causes, the study suggests.

Cardiovascular benefit of exercise in the prevention of heart disease and stroke is more established, but the authors believe their study is the first to demonstrate a predictive relationship between levels of fitness and cancer incidence in addition to the study's cardiovascular disease results. They conclude:

"These findings provide further support for the effectiveness of cardiorespiratory fitness assessment in preventive health care settings.

Future studies are required to determine the absolute level of cardiorespiratory fitness necessary to prevent site-specific cancer as well as evaluating the long-term effect of cancer diagnosis and mortality in women."

"When it comes to physical fitness, the best peer pressure to get moving could be coming from the person who sits across from you at the breakfast table," says one of the authors of another study giving results on physical fitness this month.