High-Intensity Interval Training May Improve Cardiorespiratory Fitness After Stroke

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Short-interval high-intensity interval training (HIIT) may be more effective in improving individuals’ cardiorespiratory fitness (measured as VO₂peak) after a stroke than traditional moderate-intensity continuous training (MICT), according to new research published in Stroke.¹

In the multisite 12-week randomized clinical trial, researchers observed a significant group-by-study time point interaction for VO₂peak at 12 weeks, with the HIIT group experiencing greater gains (average change 3.52 mL/kg per minute, 95% CI 2.47-4.57; P < .001) compared with the MICT group (average change 1.71 mL/kg per minute, 95% CI 0.55-2.86; P = .001; mean between-group difference 1.81, 95% CI 0.58-3.04; P = .0004).¹

Eight weeks after the conclusion of the exercise interventions, investigators reported no significant difference in VO₂peak between the 2 groups (mean difference 1.08, 95% CI –0.26 to 2.42; P = .11). Moreover, there were no significant group-by-study time point interactions between the interventions in cardiovascular risk factors, 6-minute walk test, and 10 m gait speed, according to the study published online August 7, 2024.¹

Investigators also noted that the observed improvements in VO₂peak with HIIT in individuals poststroke was clinically meaningful and within ranges associated with reduced risk for incident stroke and stroke-related hospitalization.¹

“This is the first randomized trial to examine a time-efficient, high-intensity interval training program to incorporate a phased and progressive approach,” senior author Ada Tang, PhD, a physiotherapist, professor and assistant dean of rehabilitation science at McMaster University in Hamilton, Ontario, Canada, said in an American Heart Association press release. “We also used an adaptive recumbent stepper, which we believe allowed more people to participate in high-intensity interval training, even those who cannot walk fast enough or long enough on a treadmill.”²

Cardiovascular risk factors—including low VO₂peak, hypertension, and obesity—along with emerging risk biomarkers such as arterial stiffness account for 87% of stroke risk, according to Tang and colleagues. Modifiable risk factors (eg, low levels of exercise and exercise participation) also contribute to increased stroke risk. Promoting physical activity to improve VO₂peak is an essential secondary prevention strategies.¹

With limited evidence supporting the impact of HIIT in improving VO₂peak after stroke, investigators conducted the current study to compare the effects of short-interval HIIT and MICT on VO₂peak, cardiovascular risk factors (carotid-femoral pulse wave velocity, blood pressure, and waist-hip ratio), and mobility outcomes (6-minute walk test, 10 m gait speed) in persons ≥6 months poststroke.¹

A total of 82 participants (mean age, 64.9 years; 39% women) were randomly assigned to either HIIT or MICT conducted 3 times per week for 12 weeks, with an additional 8 weeks of follow-up. Exercise training for both groups was conducted on adaptive recumbent steppers (NuStep T4r, NuStep LLC).¹

The HIIT intervention involved 10 1-minute exercise intervals, separated by 9 1-minute low-intensity intervals. The intervention targeted a heart rate reserve of 80% and increased by 10% every 4 weeks up to 100%, whereas the low-intensity intervals targeted a 30% heart rate reserve.¹

The MICT intervention included a traditional protocol for continuous training for stroke rehabilitation, with a targeted heart rate reserve of 40% for 20 minutes and progressed by 10% and 5 minutes every 4 weeks, up to a heart rate reserve of 60% for 30 minutes.¹

Participants attended 82% of visits and no adverse events were reported during the study period, according to the study.¹

Researchers noted a few limitations to their study, including the fact that the outcome assessment was unblinded at follow-up and participants were high functioning after their respective strokes. “Future HIIT research should examine people poststroke with more severe impairments in physical function or cardiovascular risk,” they wrote.¹

References:

1. Moncion K, Tang A, Rodrigues L, et al. Cardiorespiratory fitness benefits of high-intensity interval training after stroke: A randomized controlled trial. Stroke. Published online August 7, 2024. doi:10.1161/STROKEAHA.124.046564
2. Short, intense bursts of exercise more effective after stroke than steady, moderate exercise. News item. American Heart Association. August 8, 2024. Accessed August 9, 2024. https://newsroom.heart.org/news/short-intense-bursts-of-exercise-more-effective-after-stroke-than-steady-moderate-exercise