Doctors cannot stress it enough: exercise is good for you in just about any way. However, researchers note that it is important not to over-exert yourself. Workouts should be limited to 50 minutes a day so that exercisers do not overexert their hearts.

In an editorial published in the journal Heart, researchers note, "The prevailing logic held that aerobic exercise is clearly good for one's health and that, if some is good, more must be better. In 1975, Dr Thomas Bassler, a physician/runner, boldly proclaimed that, if you could run a marathon, you were immune to death from coronary heart disease (CHD).2 This urban myth has long since been disproven; indeed an emerging body of evidence suggests the opposite: extreme endurance exercise may exact a toll on cardiovascular (CV) health."

Like many things in life, exercise is best done in moderation. Authors of the editorial used two recent studies to back up their advice. One study examined the health of 50,000 people over 30 years. The study found that the 14,000 runners involved in the study were 19 percent less likely to die over the course of the trial.

However, closer analysis of the study found that those benefits were limited to people who ran between five and 20 miles a week.

For people who exerted themselves for longer distances, they did not benefit any more than people who did not run at all.

The study also found the same results for people who ran more quickly. Those who saw the most benefit were people who ran at a comfortable speed at about six to seven miles per hour.

The studies found that people who ran between two to five times a week saw a greater benefit than those who pounded the pavement daily.

A second study conducted with 20,000 Danish participants found that slow joggers saw the greatest health benefits.

Many people's lifelong dream is to run a marathon and researchers do not discourage that. Instead, they say to limit the fulfillment of that dream to once or twice in a lifetime, rather than an annual occurrence.