Previously sedentary, middle-aged adults who devote themselves to regular aerobic exercise for two years can increase their maximal oxygen uptake and decrease cardiac stiffness, according to new research published in Circulation.

The study, led by Benjamin D. Levine, MD, suggests regular exercise training in middle age can reduce or even reverse cardiac consequences of a sedentary lifestyle. Levine and colleagues noted the commitment to a routine exercise schedule may protect against heart failure with preserved ejection fraction by preventing the stiffening of the heart.

“The key to a healthier heart in middle age is the right dose of exercise, at the right time in life,” Levine said in a press release. “We found what we believe to be the optimal dose of the right kind of exercise, which is four to five times a week, and the ‘sweet spot’ in time, when the heart risk from a lifetime of sedentary behavior can be improved—which is late-middle age. The result was a reversal of decades of a sedentary lifestyle on the heart for most of the study participants.”

The researchers studied 53 adults aged 45 to 64, but with an average age of 53. Participants were all healthy but sedentary at the start of the study; individuals were excluded if they exercised for more than 30 minutes at least three times per week.

Study participants were divided into an exercise group and a control group. The exercise group committed to moderate- and high-intensity aerobic exercise at least four days per week, while the control group participated in yoga, balance training and weight training three times per week. In addition to endurance training, the exercise group was prescribed two strength training sessions per week, mostly focused on entire body and core training.

Individuals in the exercise group experienced an 18 percent increase in maximal oxygen uptake and a notable decrease in left ventricular stiffness. The control group didn’t experience significant changes in either area.

“We found that exercising only two or three times a week didn’t do much to protect the heart against aging,” Levine said. “But committed exercise four to five times a week was almost as effective at preventing sedentary heart aging as the more extreme exercise of elite athletes.”

Levine said the exercise program is particularly effective in late-middle age because the heart still has plasticity and can therefore reverse the effects from years spent on the couch.

The key is making exercise part of a routine, Levine said, and following a formula similar to the one used in the study: a mixture of at least one long session per week (an hour of tennis, cycling, running, brisk walking, etc.); one high-intensity, interval-training session; two or three days of moderate-intensity exercise, and at least one weekly strength training session.

“That’s my prescription for life, and this study really reinforces that it has quite extraordinary effects on the structure and function of the heart and blood vessels,” he said.

Most of the study participants were white, limiting the ability to generalize the results to other populations, the authors noted. In addition, only volunteers who were healthy and able to devote the time for the intensive exercise regimen were selected, so the findings may not apply to the entire adult population.