HIIT Fit and Strong

HIIT Takes a Hit in an RCT for Certain Heart Patients

Google Trends: High Intensity Interval TrainingHigh intensity interval training (HIIT) is hot right now. It mixes short periods of very intense exercise with less intense recovery. Even before the pandemic, interest in HIIT had grown dramatically. Then it spiked when pandemic lockdowns began. But a new RCT published yesterday in JAMA suggests that it might not be a panacea for everyone.

Specifically, in an RCT with patients with heart failure, Stephan Mueller and colleagues found no clear advantage for HIIT over moderate continuous training.


Almost half of patients with heart failure have a normal ejection fraction. The term for this is heart failure with preserved ejection fraction (HFpEF). The heart contracts and pumps normally, except that it pumps less blood with each beat because it is stiff and not filling with as much blood as a healthy heart. HFpEF has become much more common as obesity rates have grown.

The Mueller study focused on patients with HFpEF.

An RCT of HIIT vs Moderate Continuous Exercise Training

The researchers randomized 180 patients to three different groups. One group received HIIT for 38 minutes three times per week. Another group received moderate continuous training for 40 minutes five times per week. Finally, the control group received one-time advice on guidelines for physical activity. The exercise groups did three months of their regimens in the clinic, followed by nine months of telehealth supervised home exercise.

The primary endpoint was improvement in peak VO2. This measure of cardiorespiratory fitness has long been the gold standard for assessing the prognosis of heart failure patients. Both exercise regimens delivered improvements in fitness versus the control group after 12 months. However, the HIIT results were not superior to the moderate exercise training program.

So What?

This RCT does not deliver the result that HIIT fans would like to see. The high intensity training was not obviously superior to a more moderate regimen in these heart failure patients. In fact, Ambarish Pandey and Dalane Kitzman say in an editorial alongside this study:

“These data suggest that moderate continuous training may be the preferred exercise training approach in older patients with HFpEF.”

So HIIT is not a panacea for every person seeking to improve their fitness. For these heart failure patients, fitness training is clearly helpful. The insight here is that HIIT is not clearly superior in this case. In many situations, the appeal of fewer, shorter sessions with HIIT will likely continue to appeal.

For both fitness and diet, it is rare to find a single approach that works best for everyone.

Click here for the study and here for the editorial. For further perspective on this study, click here. For more on comparisons of HIIT and more moderate exercise, click here.

HIIT Fit and Strong, photograph © kevinzahri / flickr

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February 10, 2021