As in most everything, too much exercise--normally a very good thing--can actually be bad for you.
Even though a key part of managing high blood pressure and heart disease, new animal research suggests there can be too much of this good thing. The August edition of the journal Hypertension reports that researchers from the University of South Dakota found in experiments with rats that excessive exercise worsened high blood pressure and led to progression to heart failure in rats with high blood pressure.
Because of all the previous findings about the benefits of exercise, these new findings in rats are unexpected. An editorial published with the study says that the implications for humans are not yet certain. Dr. Paul Christian Schulze, of Boston University Medical Center, and Satyam Sarma of Brown University Medical Center in Providence, Rhode Island warn that the findings "should raise our awareness" of the potential harm intense exercise might do to people with untreated high blood pressure.
Researchers found that rats which 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. It's likely that the rats "simply exercised too much."
It's obvious that scientists and clinicians now need to focus on defining the fine line between beneficial and detrimental effects of exercise.