For some, exercise can increase health risk

Exercise may increase heart risk for some, a study has found.

Scientists analyzed data from six exercise studies including 1,687 people to find that close to 10 per cent showed worse blood pressure, insulin levels, HDL cholesterol or triglycerides, all of which are related to heart disease.

The direct cause, however, remains unknown.

"It is bizarre," said Claude Bouchard, lead author of the paper and a professor of genetics at Louisiana State University.

Authors of the study also warned that the study results should not become an excuse not to exercise.

They advised that people continue to exercise as before, but also consider getting checked on heart disease risk factors on a regular basis.

The paper was published on Wednesday in the journal PLoS One.