Regular exercisers and endurance athletes live about three to six years longer than the general population. But what is conferring this survival advantage: simply being more active or working hard enough to experience improvements in aerobic fitness?

Activity versus fitness

To find out, researchers compared the cardiovascular benefits of progressive levels of physical activity versus the body’s ability to take in and use oxygen, or what we more commonly call aerobic fitness. They found that the most physically active people had a 30 percent lower risk of heart disease than the least active, showing that physical activity of any kind is beneficial.

But it’s not nearly as effective as improving fitness. There was a 64 percent decline in the risk of heart disease from the least to the most fit participants. Put another way, a low level of fitness or aerobic capacity increases the risk of heart disease more than twice that of merely being physically inactive. Subsequent studies have shown that aerobic capacity is one of the strongest prognostic markers in people with and without heart disease. At any given risk-factor profile, low-fit individuals are two to three times more likely to die during the study follow-up than their more fit counterparts.

Implications for the exerciser

In these studies, fitness level is measured by metabolic equivalents (METs). One metabolic equivalent (MET) equals the amount of oxygen your body uses at rest. A person with a fitness level that is less than 5 METs (or five times the energy expenditure at rest) generally has a higher risk of mortality. Examples of lower METs activities include billiards and bowling (2 to 3 METs) and bicycling at 5 to 6 miles per hour (mph; 2 to 4 METs).

In contrast, an aerobic capacity of 8 to 10 METs or higher signifies an excellent long-term prognosis. That’s equivalent to participating in activities such as bicycling at 12 to 14 mph, jogging at 6 mph, or playing competitive handball or squash.

Start small

If you’re not yet fit, don’t worry: It doesn’t take a lot of work to see big rewards. The biggest reductions in the risk of heart disease are seen in people who move from the “lowest” (bottom 20 percent) to the “low” (below average) aerobic capacity category. To do that, you just need to regularly exercise at 3 METs or higher. That is the equivalent of walking on a flat treadmill at 3 mph or on a 3.5 percent grade at 2 mph. Other comparable activities include bicycling at 6 mph, golf (pulling a golf bag), or pushing a light power mower.

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