Near all studies on the matter show that regular moderate exercise improves health and extends healthy life span, though the effects on overall life span are mixed, unlike the data for calorie restriction. With the advent of small, cheap accelerometers, the research community is now making headway into determining the dose-response curve for exercise, the degree to which more is better:
The majority of citizens in developed countries should not be concerned by potential harm from exercise but rather by the lack of exercise in their lives. Small amounts of physical activity, including standing, are associated with a lower risk of cardiovascular disease, but more exercise leads to even greater reduction in risk of death from cardiovascular disease. "The evidence with regard to exercise continues to unfold and educate the cardiovascular clinical community. The greatest benefit is to simply exercise, regardless of the intensity, while the danger is two-fold: to not exercise at all or to exercise intensely, without due preparation." Studies have shown that regular physical activity reduces a person's risk of death from cardiovascular disease; however, only half of U.S. adults meet the federally recommended guidelines of 150 minutes per week of moderate intensity exercise or 75 minutes per week of vigorous intensity exercise.
Scientists examined recent research on the volume and intensity of aerobic exercise required for favorable cardiovascular health. With the rise in participation in endurance races over the past three decades, they also address the question of whether or not there is an amount of exercise that increases cardiovascular disease risk. They found that moderate and vigorous intensity exercise in amounts lower than the 2008 Physical Activity Guideline recommendations still significantly lower mortality risk in different populations around the globe. Increasing the amount of moderate intensity exercise a person engages in results in increased reductions in cardiovascular disease mortality; however, the reductions in cardiovascular mortality benefits from vigorous intensity exercise do level out at a certain point.
There is no evidence for an upper limit to exercise-induced health benefits and all amounts of both moderate and vigorous intensity exercise result in a reduction of both all-cause and cardiovascular disease mortality compared to physical inactivity. While controversial, a few limited studies have raised the concern that high volumes of aerobic exercise may be as bad for cardiovascular outcomes as no exercise at all. Researchers suggest that the possibility that too much exercise training could be harmful is worthy of investigation, but research results show that even for the very active, life-long endurance athletes, the benefits of exercise training outweigh the risks.