Chronic heart failure patients and hard-core athletes may share a bond: the pain they experience.

In both cases, scientists from Columbia University Medical Center found, calcium leaks into muscle cells, which slows muscle contraction and activates an enzyme that weakens muscle fibers. That is part of the reason high-level swimmers, cyclers, and marathon runners often feel extremely exhausted after continued physical exertion. A similar effect was detected in patients with heart failure.

The results don’t mean, however, that a sedentary lifestyle is better for your health.

“We only saw the leak in animals and human athletes that exercised three hours a day at very high intensities for several days or weeks in a row until they were exhausted,” researcher Andrew Marks, a professor of physiology and cellular biophysics at CUMC, wrote in a press release upon announcement of the study. “The study does not mean exercise is bad for you.”

For athletes, any muscle damage is usually quickly repaired. But this does not happen for heart failure patients and debilitating pain can result.

The researchers were able to develop a drug that has improved muscle performance after exertion, at least in mice. The drug, which prevents calcium leakage, could one day be used for human patients with heart failure. It may also be potentially used to boost human endurance, as it allowed mice who were made to undergo intense daily swimming trials to remain vigorous and retain healthy muscles.