High-intensity interval training (HIIT) significantly enhances aerobic fitness in stroke survivors compared to conventional moderate-intensity continuous training (MICT), according to a recent multicenter randomized controlled trial.
The study, published on August 7 in Stroke, reveals that HIIT, involving repeated one-minute bursts of high-intensity exercise, provides greater improvements in cardiovascular fitness than traditional continuous exercise. Ada Tang, PT, PhD, an associate professor at McMaster University in Hamilton, Ontario, led the research. “We anticipated seeing improvements with HIIT, but the extent of the gains was remarkable,” Tang told Medscape Medical News. “The HIIT group’s improvements were double those of the MICT group.”
Researchers compared the effects of a 12-week HIIT regimen with those of MICT on peak oxygen uptake (V̇O2peak), cardiovascular risk factors, and mobility after stroke. Participants were randomly assigned to three days per week of either HIIT or MICT, with an average age of 65 years and 39% female. Participants began the study a mean of 1.8 years post-stroke and were enrolled on adaptive recumbent steppers.
The HIIT protocol consisted of 10 one-minute high-intensity intervals (targeting 80% heart rate reserve, HRR) interspersed with nine one-minute low-intensity intervals (targeting 30% HRR), totaling 19 minutes. This protocol progressively increased intensity every four weeks. Conversely, the MICT protocol targeted 40% HRR for 20 minutes, increasing to 60% HRR over 12 weeks.
Results showed that the HIIT group experienced a 3.5 mL/kg/min improvement in V̇O2peak, twice as much as the 1.8 mL/kg/min increase in the MICT group. Notably, the HIIT group’s improvements remained above the clinically significant threshold of 1.0 mL/kg/min at the eight-week follow-up, unlike the MICT group’s 0.67 mL/kg/min.
Both groups demonstrated similar increases in the six-minute walk test—8.8 meters at 12 weeks and 18.5 meters at 20 weeks—without significant differences in cardiovascular risk factors or mobility outcomes. No adverse events were reported in either group.
While the HIIT group spent 36% of training time at intensities exceeding 80% HRR, the MICT group spent 42% of time at 40%-59% HRR. Despite the promising results, the study’s limitations include a small sample size of high-functioning individuals who experienced mild strokes and a two-year enrollment halt due to COVID-19, affecting statistical power.
Tang emphasizes that despite these limitations, HIIT represents a viable alternative to traditional MICT for stroke rehabilitation, potentially offering significant short-term benefits. “Although HIIT shows promise, clinicians must consider each patient’s individual health and physical condition before recommending it,” Tang advises. “Stroke rehabilitation specialists can provide guidance to ensure the safe and effective implementation of HIIT.”
Ryan Glatt, CPT, a senior brain health coach at the Pacific Neuroscience Institute, cautions that the applicability of these findings to more severely impaired stroke survivors remains uncertain. “The study focused on relatively high-functioning individuals, so more research is needed to evaluate HIIT’s effectiveness for a broader range of stroke survivors and the long-term sustainability of its benefits,” Glatt told Medscape Medical News.
Glatt notes that while HIIT has potential, it should be used selectively. “Replacing traditional exercise protocols with HIIT should not be a blanket recommendation. Robust evidence and careful patient assessment are crucial.”
The study was funded by the Canadian Institutes of Health Research. Tang has reported grants from the Canadian Institutes of Health Research, the Physiotherapy Foundation of Canada, and the Heart and Stroke Foundation of Canada. Glatt declared no relevant financial relationships.
