KEY POINTS:
Although exercise can be a key part of managing high blood pressure and heart disease, new animal research suggests there can be too much of a good thing.
In experiments with rats, researchers found that excessive exercise worsened high blood pressure and progression to heart failure in rats with high blood pressure. Rebecca Schultz and colleagues at the University of South Dakota, Sioux Falls, reported the results in the journal Hypertension.
Regular physical activity has been linked to a lower risk of heart disease in numerous studies. Moreover, exercise therapy has been shown to improve blood pressure and symptoms of heart failure - a chronic condition in which the heart loses its ability to pump blood efficiently, causing symptoms like breathlessness and fatigue.
The new findings in rats were, therefore, unexpected, said an editorial accompanying the study.
The implications for humans are not yet certain, according to the editorialists Paul Christian Schulze of Boston University Medical Centre, and Satyam Sarma of Brown University Medical Centre in Providence, Rhode Island. However, the findings "should raise our awareness" of the potential harm intense exercise might do to people with untreated high blood pressure.
Humans, as well as rats, develop high blood pressure that can progress to heart failure. In the study, some of the animals were housed with a running wheel, while the others remained sedentary.
Dr Schultz and her colleagues found the rats that lived with a running wheel tended to exercise excessively. The results, over time, were structural abnormalities in the heart and a reduced pumping ability - all of which were worse in the active animals than in the sedentary ones.
The study authors say the reasons for the findings are unclear but it's likely the rats "simply exercised too much".
The study raises the possibility that "uncontrolled and excessive exercise" may negatively affect the heart in people with high blood pressure, potentially speeding the onset of heart failure.
The study also notes that some of the questions for future studies is whether this is true among people whose blood pressure is under control with medication.
- Reuters
