Scientists had already discovered that stem cells could be coaxed into producing new tissue through injections of chemicals known as growth factors, but the new study is the first to suggest that a simple exercise programme has a similar effect.
The findings suggest that damage from heart disease or failure could be at least partially repaired through 30 minutes of running or cycling a day, at enough intensity to work up a sweat, The Telegraph reported.
An early-stage study on healthy rats showed that an equivalent amount of exercise resulted in more than 60 per cent of heart stem cells, which are usually dormant in adults, becoming active.
After two weeks of exercise the mice had a seven per cent increase in the number of cardiomyocites, the "beating" cells in heart tissue, researchers reported in the European Heart Journal.
The team from Liverpool John Moores University said they would now study the effects on mice which had suffered heart attacks to determine whether it could have an even greater benefit.
"The exercise is increasing the growth factors which are activating the stem cells to go on and repair the heart, and this is the first time that this potential has been shown," Dr Georgina Ellison, who led the study, said.
"We hope it might be even more effective in damaged hearts because you have got more reason to replace the large amount of cells that are lost," Ellison added.
Although some patients with severe heart damage may not be capable of intensive exercise, Ellison said a significant number would easily be able to jog or cycle for 30 minutes a day without risking their health.
"In a normal cardiac rehabilitation programme patients do undertake exercise, but what we are saying is maybe to be more effective it needs to be carried out at a higher intensity, in order to activate the resident stem cells," she said.
"This study adds to the growing evidence that adult hearts may be able to make new muscle from dormant stem cells," Professor Jeremy Pearson, associate medical director of the British Heart Foundation, which funded the research, said.
"However, much more research is now needed to find out whether what's been seen in this study can be translated into treatments for human patients," Pearson said.
