Exercise Study Hints at Volume, Intensity Levels Needed to Improve Cardiac Fitness in Middle Age

Among middle-aged, previously sedentary adults, a 2-year program involving regular, supervised, high-intensity exercise decreases cardiac stiffness and improves maximal oxygen uptake (VO2max), potentially offering protection against the development of heart failure later in life, a new study suggests.

Importantly, the same benefits were not seen among subjects randomized to a less-intense program of just 3 days a week that focused on yoga, balance, and strength training.

The findings, according to authors led by Erin J. Howden, PhD (UT Southwestern Medical Center, Dallas, TX), provide rigorous, randomized trial evidence to support the notion that “exercise is medicine” for preventing the kind of degenerative cardiac changes common in sedentary adults. “Our exercise prescription, which was evidence-based, proved to be highly effective in enhancing cardiovascular structure and function,” they write. 

Howden et al’s paper was published online earlier this week in Circulation.

Investigators randomized 61 adults (mean age 53; 48% men) to 2 years of high-intensity exercise training done four to five times per week or to the less intense 2-year program. Right heart catheterization and 3-D echocardiography, as well as tests of VO2max, were performed at baseline and follow-up.

In the high-intensity group, training sessions were ramped up gradually and ultimately tailored to the individual, with participants encouraged to use cardio machines or to participate in outdoor sports such as running, cycling, and swimming. Subjects in this group also had their heart rates monitored and worked up to doing four interval training sessions that involved bursts of activity up to their maximum heart rate.

"The key to a healthier heart in middle age is the right dose of exercise, at the right time in life," senior study author Benjamin D. Levine, MD (UT Southwestern Medical Center), commented 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,” he said. “The result was a reversal of decades of a sedentary lifestyle on the heart for most of the study participants.”

Hope for the Couch Potato

Fifty-three of 61 the randomized patients completed the study, with dropouts comparable between groups—something that speaks to the fact that this kind of intervention is sustainable, the authors note. Over the 2-year period, subjects in the high-intensity exercise group saw their VO2max increase by 18% and LV stiffness decline, both statistically significant changes from baseline. No such improvements were seen in the control exercise group. Modest decreases in body weight and fat mass were also seen in the high-intensity group but not in controls.

“Regular exercise training may provide protection against the future risk of heart failure with a preserved ejection fraction by preventing the increase in cardiac stiffness attributable to sedentary aging,” Howden et al conclude.