It is the research that couch potatoes have been waiting for - irregular bouts of strenuous exercise can seriously damage your health.
Gareth Davison and Ciara Hughes of Ulster University's School of Applied Medical Sciences and Sports Studies have been putting both fit and unfit volunteers through their paces on the treadmill.
They warn that unfit individuals who work out only sporadically, but then push their heart rate to 85 per cent of its maximum for more than ten minutes, can cause serious chemical damage to their bodies.
Aerobic exercise releases free radicals that damage cells, although athletes who regularly push their bodies to this level appear to be protected from any adverse effects.
"If you are into high-intensity exercise, you should work your way up to it and not simply plunge in," Dr Hughes said.
The results also highlighted the importance of eating healthily and ensuring a proper intake of vitamins, she said.
The UU researchers used two groups of volunteers. One was given a mixture of antioxidants, the other a placebo. Dr Davison said that while strenuous exercise caused cellular damage, the body was more susceptible to this without antioxidants such as vitamins C and E. "Natural antioxidants can be found in a balanced diet consisting of foods such as broccoli, spinach and berries," he said.
"A key lesson is, if you are involved in strenuous aerobic exercise, make sure your diet is rich in antioxidants, because they will protect against damaging your health," Dr Davison added.
But the research is not an excuse for couch potatoes to stay on the sofa.
While irregular strenuous exercise is dangerous, Dr Davison stressed the benefits of regular moderate exercise.
Pushing your heart rate up to 60 per cent of its maximum for 40 minutes three or four times a week protected against a range of chronic diseases, he said.