We’ve been told that high-intensity workouts offer more cardiovascular benefits than moderate exercise. Norwegian researchers now believe they know why.
“Our research on rats with heart failure shows that exercise reduces the severity of the disease, improves heart function, and increases work capacity,” says Tomas Stølen, PhD, at the Norwegian University of Science and Technology. “And the intensity of the training is really important to achieve this effect.”
Reporting in the Journal of Molecular and Cellular Cardiology, the researchers describe the intricate mechanisms required to produce a healthy heartbeat. When any one of these actions falters, it limits the heart’s ability to pump oxygenated blood throughout the body.
In the lab rats raised to develop heart failure, for instance, only about 20 percent of the available blood — known as the ejection fraction — exited the heart with each contraction. A healthy rat will push 75 percent of the blood out into its body with each beat.
After six to eight weeks of daily high-intensity interval training (HIIT), the ailing rats increased their ejection fraction to 35 percent. Stolen points specifically to improvements in the transfer of calcium in the heart’s cell membranes to explain the change.
“We found that interval training improves a number of the mechanisms that allow calcium to be pumped out of the cells and stored more efficiently inside the cells,” he explains.