Researchers randomized patients with PAD to follow a low-intensity (n=116) or high-intensity (n=124) home-based walking program for one year, or to join a control group with no exercise program (n=65). The primary endpoint was mean distance change in a 6-minute walking test, with a change of 8 to 20 meters considered the minimum clinically important difference.
At 12 months, participants in the high-intensity walking group experienced a mean improvement of 35.5 meters in the 6-minute walking test. By contrast, those in the low-intensity walking group and the non-exercise group experienced similar decreases in mean distance covered of 6.4 meters and 15.1 meters, respectively.
"Based on the results of this trial, it appears that inducing ischemia of the leg muscles may be necessary to attain benefit from exercise in people with peripheral artery disease," said lead study author Dr. Mary McDermott of the Northwestern University Feinberg School of Medicine in Chicago.
"It is important to note that those randomized to the high-intensity exercise had significantly greater gains in six-minute walk distance, even though they walked for exercise about half as many minutes as those randomized to the low-intensity exercise intervention," Dr. McDermott said by email.
Participants assigned to the exercise groups met with a coach and received instruction on how to use an accelerometer to track walking intensity. Both groups were asked to walk unsupervised, five times per week, for up to 50 minutes per session. The low-intensity walkers were told to walk comfortably and avoid ischemic leg discomfort; high-intensity walkers were advised to use a pace that induced maximum tolerable ischemic leg symptoms.
One limitation of the study is that 18% of participants were lost to follow-up and didn't report for 12-month assessments, the study team notes. Researchers also could not administer 12-month treadmill stress tests after March 13, 2020, due to the COVID-19 pandemic, which led to missing data.
Results from a home-based exercise program also may not be representative of what would happen with supervised treadmill workouts, the authors note in JAMA.
Walking also likely had benefits for people in the low-intensity exercise group even though this isn't reflected by the primary outcome of the study, said Dr. Joseph Ladapo of the David Geffen School of Medicine at University of California, Los Angeles.
However, the results do underscore the importance of more-intense exercise, Dr. Ladapo, who wasn't involved in the study, said by email.
"I think what we are seeing is something that people who exercise or compete in sports already know, which is that improving your performance often means pushing toward your physical boundaries," Dr. Ladapo said. "The low-intensity home-based exercise intervention may not have been vigorous enough to elicit the same type of benefits as the high-intensity intervention."
SOURCE: https://bit.ly/2R1VXHB JAMA, online April 6, 2021.
By Lisa Rapaport
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