A new study has demonstrated that short bursts of high-intensity interval training (HIIT) were more effective than traditional, moderate continuous exercise for improving the body’s aerobic fitness after a stroke.
One-minute, short bursts of HIIT for 19 minutes may be more effective for improving fitness among people six months or more after a stroke. This is compared to traditional, 20-30 minutes of moderate-intensity exercise sessions.
The research, published in Stroke, the peer-reviewed scientific journal of the American Stroke Association, a division of the American Heart Association, found that the study HIIT group’s cardiorespiratory fitness levels improved twice as much as the moderate intensity continuous training group.
“This study shows that people with stroke can also benefit from high-intensity interval training,” said Kevin Moncion, Ph.D., a physiotherapist who led this study as part of his doctoral studies at McMaster University in Hamilton, Ontario, Canada.
“With the right support and guidance, stroke survivors can safely and effectively engage in high-intensity interval training, significantly improving their overall health and recovery.”
The study
The multi-site trial took place between September 2018 and March 2024 and included stroke survivors between six months to five years after a stroke.
Researchers randomly grouped participants to receive either three days per week of 12 weeks of high-intensity interval training or three days per week of 12 weeks of traditional moderate exercise sessions.
The high-intensity interval training protocol involved 10 one-minute intervals of high-intensity exercise, interspersed with nine one-minute low-intensity intervals, for 19 minutes total. The moderate intensity continuous training involved 20 to 30 minutes of steady exercise at moderate intensity.
Researchers then compared fitness levels, cardiovascular risk factors such as blood pressure and stiffness of blood vessels, walking speeds and distances between the two groups. All assessments were repeated one final time 8 weeks after the exercise interventions to evaluate whether the changes were sustained over time.
As well as discovering that the HIIT group’s cardiorespiratory fitness levels improved twice as much as the moderate intensity continuous training group, the team found the improvement in the high intensity interval training group stayed above clinically important thresholds even at the eight-week follow-up, whereas the moderate intensity continuous training group did not.
The team also discovered that both the high intensity interval training and moderate intensity continuous training groups gained improvement in walking endurance, as measured by distance walked over six minutes.
At baseline both groups could walk about 355 meters over six minutes, and after 12 weeks of exercise both groups increased their walking distance by eight metres and after the eight-week follow-up they increased their walking distance by 18 meters.
“This is the first randomised trial to examine a time-efficient, high intensity interval training program to incorporate a phased and progressive approach,” said senior author Ada Tang, Ph.D., a physiotherapist, professor and assistant dean of Rehabilitation Science at McMaster University.
“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.”
The limitations of the study include that study participants were higher functioning stroke survivors from a physical standpoint who were at lower risk for heart disease. Study minimum criteria included the ability to walk 10 meters without physical assistance of another person, although the use of cane or walker was permitted.
Outcome assessments were unblinded at follow-up, which may have influenced results. Lastly, enrollment and exercise for the trial was halted two years for COVID-19 lockdowns, thus inflating the rate of participants who left the study and potentially limiting the statistical power of the analysis.
the team has suggested that future research should examine stroke survivors with more severe impairment in physical function or heart disease risk, according to the study authors.
“Stroke rehabilitation professionals now have evidence to support implementing short, high-intensity interval training protocols in clinical practice. We showed our program is safe and effective at improving fitness and walking distance in people after stroke, which are important outcomes for stroke survivors,” Tang said.
