Women Find Strength with Cardiac Rehab

HIIT exercise is a key piece of recovery after a cardiac event.
woman at cardiac rehab

When cardiologist Sherrie Khadanga, MD, first came to The University of Vermont Medical Center for her residency in 2013, she started researching cardiovascular risk factors and ways those could be reduced. She realized there was a lot of attention given to medications, stents and surgeries in the medical literature, but not as much on cardiac rehab programs – which she thought was unfortunate.

“Cardiac rehab decreases hospitalization and mortality, improves patients’ quality of life, and reduces the likelihood of a second cardiac event. It’s a simple program with a huge beneficial impact,” she explains.

Dr. Khadanga also noticed a couple of concerning trends when it came to the women she saw in her cardiac rehab programs.

“First, women don’t tend to do cardiac rehab as often as men. And second, when women do come to rehab, they don’t seem to improve as much as men,” she says.

She could make some guesses as to why the first part was the case: women, as the typical primary caregivers, may not be comfortable devoting that much time to exercise; and maybe women, and particularly older women, may not be as comfortable with exercise equipment.

But she was puzzled by the second part. When she solicited a colleague’s opinion, she was surprised by what she heard.

“I sat down with one of our exercise physiologists, and his theory was that we tend to incorporate high-intensity interval training (or HIIT) in cardiac rehab programs for men, but not for women.”

HIIT has been shown to be more effective than moderate exercise in increasing peak oxygen intake, which is a key marker of heart health. However, the majority of those studies have involved mostly men. 

“My colleague also went on to note that we, as doctors, have an inherent bias that women can’t do this. He said, ‘HIIT has this connotation that it’s just for fitness junkies.’ In full disclosure, that irritated me. I thought, if it works, we should push it, and we should make it more routine for women.”

So Dr. Khadanga decided to put some data behind it.

She ran a randomized clinical trial between July 2017 and February 2020, involving 56 women in cardiac rehab programs at UVM Medical Center. One group of patients combined HIIT – exercising at intervals ranging from 70% to 95% of peak heart rate (HR) – with lower-extremity resistance training, three times per week over 12 weeks. The other group followed the current standard, which is 45 minutes of moderate continuous exercise.

The fact that the study involved both HIIT and resistance training made this research unique, Dr. Khadanga says. It’s also significant, because women in particular tend to lose muscle mass in their lower extremities as they age. Strength training in the legs helps to improve stamina and ability to exercise.

When the study was published in JAMA Cardiology in February of 2022, the results showed that all 56 patients in the study improved their overall fitness level, emphasizing the benefit of cardiac rehab. But those in the experimental group – who did HIIT with resistance training – improved 23% more than those in the control group, which is a statistically significant difference.

While she notes that larger studies are needed, involving a more diverse group of patients, she says this study has “created a conversation,” both about the dangers of underestimating women’s ability to successfully complete robust cardiac rehab programs, and about the need to include more women in medical studies, especially in the field of cardiovascular health.

Dr. Khadanga summarizes the study this way: “Why don’t women improve as much as men? Because we train them differently. And we shouldn’t. This study involved women aged 43 to 98, and there were no major injuries or cardiac events. Yes, this is an older population with a lot of underlying conditions. And, they can absolutely do this.”

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