HIIT may be more effective than moderate exercise after a stroke

• Stroke is a condition where blood and oxygen are not able to get to the brain.
• Exercise is an important part of stroke recovery.
• Researchers from McMaster University have found that repeated one-minute bursts of high intensity interval training (HIIT) were more effective in improving aerobic fitness after a stroke than traditional, continuous moderate exercise.

Each year, about 15 million people around the world have a stroke — a condition where blood and oxygen is not able to get to the brain.

While stroke is treatable, researchers estimate that more than two-thirds of stroke survivors will require rehabilitation, which depending on the person’s needs can include speech, occupational, and physical therapies.

Previous studies show that exercising after a stroke offers several health benefits, including reduced risk of stroke recurrence and improved overall recovery .

A recent study found that repeated one-minute bursts of high-intensity interval training (HIIT) was more effective in improving aerobic fitness after a stroke than traditional, continuous moderate exercise.

“Stroke is a leading cause of death and disability worldwide, but there is strong evidence to support exercise as a key component of rehabilitation programs to promote recovery and reduce long-term impacts of stroke and lower risk of future recurrent stroke,” said Ada Tang, PT, PhD, physiotherapist, professor, and assistant dean of Rehabilitation Science at McMaster University and corresponding author of the study.

“Research has shown that aerobic fitness levels are low in people with stroke, often at levels that are inadequate to perform activities we might do every day such as climbing stairs or walking fast,” Tang explained to Medical News Today . “We know that there are challenges to participating in exercise after stroke, however, such as finding time to fit it into their day.”

“We also know that therapists can be hesitant to push patients with stroke to higher intensities of exercise despite research that suggests that more intense exercise may be beneficial. Instead, they are more likely to keep exercise intensities lower. We felt that HIIT would be an important, feasible, and time-efficient option for exercise after stroke,” she added.

The study is published in the journal Stroke .

12 weeks of HIIT vs. moderate exercise

For this study, researchers recruited 82 stroke survivors who were in the period between six months and five years after a stroke.

Study participants were randomly grouped to either receive HIIT or moderate exercise sessions for three days of the week over 12 weeks.

“Both groups exercised three times per week on non-consecutive days for 12 weeks,” Tang detailed. “Both groups included three minutes of warm-up and two minutes of cool down. All exercise was performed on a recumbent stepper machine (NuStep).”

“For participants in the HIIT group, the exercise protocol was 10 one-minute intervals of high-intensity exercise (80-100%) interspersed with nine one-minute intervals of lower intensity recovery (30%),” she continued. “Exercise time, not including warm-up and cool-down, was 19 minutes. The moderate-intensity continuous exercise sessions were 40-80% intensity for 20-30 minutes.”

Improved cardiorespiratory fitness levels experienced with HIIT

At the study’s conclusion, scientists found that the cardiorespiratory fitness levels — the maximum amount of oxygen a person can take in during exercise — of participants in the HIIT group improved twice as much as those in the moderate exercise group.

“We expected to observe greater improvements in fitness levels in the HIIT group but were excited to see how much they did improve,” Tang said. “The improvements in fitness levels in the HIIT group were within the range of values associated with lower risk of hospitalization and stroke.”

Additionally, researchers found that this improvement stayed above clinically important thresholds in the HIIT group eight weeks after the end of the study, which was not the same case for the moderate exercise group.

“This finding is important as it means that the gains made after HIIT were maintained to a greater extent than after moderate-intensity continuous training. Nonetheless, it is important that regular exercise becomes part of a lifelong healthy lifestyle after stroke given that people with stroke are at higher risk of having another one in the future.”
— Ada Tang, PT, PhD

“We believe that the higher intensities achieved (are the) key difference. By using an interval training format where bursts of high-intensity exercise is interspersed with recovery intervals of lower intensity, we can achieve the benefits of more intense exercise without risk of over-fatigue. We will continue to examine innovative ways to promote exercise and physical activity after stroke to reduce the global burden of this condition,” Tang said.

New ways of stroke recovery enhance quality of life

After reviewing this study, Christopher Yi, MD , a board certified vascular surgeon at Memorial Orange Coast Medical Center in Fountain Valley, CA, told MNT he found it to be of interest and excitement.

“This study shows that high-intensity aerobic exercise can significantly improve cardiovascular fitness in stroke patients, which is a substantial long-term benefit for stroke recovery,” Yi explained.

“Patients who [experience] strokes are often severely debilitated, with poor (quality) of life and decreased longevity. Finding better ways to enhance the recovery of strokes will improve the quality of these patient’s lives, reduce the risk of recurrent strokes and cardiovascular events, and ultimately increase survival rates .”
— Christopher Yi, MD

“I would like to see how patients with more severe physical impairments after a stroke perform with HIIT. I would also like to see long-term outcomes of this study beyond eight weeks, including overall quality of life. Lastly, I would like to understand the underlying biological mechanisms from HIIT, including cardiovascular function and neuroplasticity,” he added.

MNT also spoke with Ryan Glatt, CPT, NBC-HWC , senior brain health coach and director of the FitBrain Program at Pacific Neuroscience Institute in Santa Monica, CA, about this study.

“The study is intriguing but raises questions about the generalizability of HIIT benefits for a broader stroke population,” Glatt said. “Improving aerobic fitness is essential to reduce the risk of secondary strokes, but the study’s participant pool limits the broader application of its findings. Future research should include more diverse and severely impaired stroke survivors to truly validate HIIT’s effectiveness and long-term impact.”