Medscape Medical News
Sean Hyson, CSCS
August 28, 2024
If you encourage patients coming back from stroke to exercise, you’re doing the right thing. Regular physical activity can help improve recovery and reduce the risk for another stroke.
But emerging evidence suggests that post stroke, patients may be capable of working out much harder than previously thought — and the benefits can be worth the extra effort.
The latest such study, published this month in Stroke and reported on Medscape Medical News, indicated that briefer, more intense aerobic workouts — compared with longer, moderate-intensity training sessions, which have long been the standard prescription for post-stroke exercise — may help stroke survivors dramatically improve their fitness.
When Canadian researchers pitted moderate-intensity aerobic training against high-intensity interval training (HIIT), participants performing HIIT made double the fitness gains after 12 weeks. These changes were associated with a lower risk for stroke-related hospitalizations, and the magnitude of the improvement has been linked to a lower risk for early death in the general population.
The study furthers an impressive but still small body of research on HIIT in post-stroke populations. A 2018 review of 10 trials determined that HIIT may improve mobility and gait, as well as cardiovascular health and neuroplasticity, post stroke. It appears to be a more time-efficient alternative to moderate, steady-state aerobics that offers similar if not superior results despite lower exercise volumes, particularly in people with heart disease.
“There’s been an evolution of aerobic exercise recommendations,” said Talya Fleming, MD, medical director of the Stroke Recovery Program and Aftercare Program at JFK Johnson Rehabilitation Institute in Edison, New Jersey. (Fleming was not involved in the new study.)
“In general, moderate-intensity exercise has been thought to be safer and more sustainable after stroke compared to high intensity,” Fleming said, “but more recent studies have been showing that HIIT is beneficial too.”
Why Intensity Matters
In addition to promoting chemicals in the body that improve cognitive and motor function, scientists have theorized that HIIT may increase the production of proteins in the mitochondria, thereby improving the efficiency of the cardiovascular system, Fleming said.
In the study, researchers recruited adults aged 40-80 years who had a stroke at least 6 months prior. They were randomized into two groups that performed aerobic training three times per week — one group did HIIT, while the other did continuous, moderate-intensity work.
Both groups improved walking endurance after 12 weeks, but the HIIT participants’ VO2 max — the rate of oxygen consumed during exercise, a measure of cardiorespiratory fitness — improved more than twice as much as that of the moderate group: 3.5 vs 1.7 mL/kg/min.
Those benefits may last longer, too. Eight weeks after the study, the scientists followed up, measuring the participants’ cardiorespiratory fitness again. Though the participants hadn’t been required to stick with the exercise regimen, and many had likely not been as active in the interim, the HIIT group’s improvements remained above clinically important thresholds, while the moderate-intensity trainees’ did not.
What This Means for Your Patients
Thanks to its efficiency and effectiveness, HIIT has already found a home with young adults and athletes for improving fitness levels. But medical professionals have understandably been hesitant to use it with more vulnerable populations.
“In the past, we were more reluctant to push patients who had had a stroke,” said Fleming, “but depending on the equipment used and modifications made, they can exercise at a high level. We’re learning that the brain and the body are capable of more than we initially believed.”
Depending on the individual, a patient may be able to do HIIT as soon as 3 months after stroke, and very likely at 6 months, said Fleming.
“We don’t want people sitting on a couch 6 months after a stroke, covered in Bubble Wrap,” Fleming said. “We want them actively participating in exercise.”
That said, there are no agreed-upon parameters yet for exactly when to do HIIT, or how best to do it, and HIIT routines must be approached with caution.
A good place to start is with a pre-exercise evaluation or stress test to determine what the patient’s heart and lungs can tolerate, Fleming recommended.
Then, consider a few key features of the study to help guide your advice.
Go Short
While this isn’t the first time HIIT has been used in a post-stroke population, a number of variables make this study stand out.
For one thing, the intervals were particularly short.
“Much of the previous research on HIIT in stroke survivors used work intervals of 3, 4, or 5 minutes,” said Ada Tang, PT, PhD, co-author of the study and associate professor and assistant dean in the School of Rehabilitation Science at McMaster University in Hamilton, Ontario, Canada. “Shorter bouts allow you to hit higher intensities. We wanted the intensity to be high, so we did what is called ‘short-interval HIIT.'”
The HIIT sessions consisted of hard 60-second high-intensity work bouts alternated with 60 seconds of lighter work to recover. Exercise intensity was gauged by percentages of heart rate reserve (HRR) — the difference between a subject’s maximum heart rate and resting heart rate. (Researchers were also guided by perceived exertion, so if a participant felt they were being pushed too hard, they were allowed to back off.)
There were 10 rounds of high-intensity bursts and nine rounds of back-off intervals, totaling 19 minutes of training. Meanwhile, the moderate-intensity workouts were done for 20-30 minutes, while maintaining a steady percentage of HRR.
“We made them work hard for 1 minute at a time,” said Tang. “Previous research shows that if you go harder, the benefits are better. Other studies have done HIIT but not for as short-duration intervals and not at as quite a high intensity — getting up to 100% of HRR.”
Use a Progressive Approach
Tang and her team didn’t know how hard they could push the participants, or if they would even be willing to train at such intensities, so they gradually ramped the intensity up over 4-week blocks.
“One thing that makes this an exciting trial is that the researchers used a planned progression,” Fleming said. “The participants didn’t do the same thing from day 1 to the end. The difficulty of the exercise progressed as the subjects’ fitness improved,” which prevented stagnation and allowed for greater results.
For the first 4 weeks, the HIIT group did their hard intervals at 80% of HRR, dropping down to 30% for the recovery rounds. In the second 4-week block, the hard intervals went up to 90%, and in the last 4 weeks, they went to 100%. The moderate-intensity group pushed their paces too, increasing their percentage of HRR in the same 4-week intervals from 40% to 50%, and finally 60%.
“Part of doing the phased, progressive approach was to build the participants’ confidence,” said Tang, so they knew they could push to 100% in the last leg of the study.
Fleming and Tang both recommended a phased, progressive approach to training, as Tang and her colleagues devised for the study.
Minimize Risks
Another key feature of the trial was the use of a recumbent stepper, which offers a seat and a backrest. This allowed the participants to train at high intensities without the risk of falling or aggravating any preexisting musculoskeletal injuries.
Though the recumbent stepper is primarily found in rehab settings, Tang said this HIIT protocol should be equally effective with any cardio equipment one has access to, provided they can perform on it safely.
No adverse effects were reported, although it should be noted that the participants had all completed stroke rehab prior to being recruited and were considered high-functioning survivors. While many were living with comorbidities (including high blood pressure or cholesterol, diabetes, and other cardiovascular conditions), all were capable of walking on their own and none were institutionalized.
As with anything else, balancing benefits with risk is important.
“Muscles are weaker after a stroke,” said Fleming, “and nerves may not function optimally. So you have to balance the benefits of HIIT with the risk of musculoskeletal injury. HIIT might help the cardiovascular system but make a person’s arthritis worse.”
“Even a recumbent stepper requires repetitive motion that could be dangerous at higher intensities,” Fleming said. “You do more reps with high-intensity exercise, and that can lead to overuse injuries.”
Consider referring your patient to a physical therapist who can modify exercise routines based on the person’s individual challenges.
The Four Pillars of Post-Stroke Fitness
Whether your patient goes for moderate- or high-intensity aerobics, that’s only one quarter of the regimen a stroke survivor should follow to reclaim their health.
The American Heart Association’s (AHA’s) Physical Activity and Exercise Recommendations for Stroke Survivors suggests that strength training, flexibility, and balance work also be included. See the Table below for their guidelines.
| Aerobic | Muscle strength/endurance | Flexibility | Balance and coordination |
| Work at 40%-70% of VO2 reserve or HRR; 55%-80% HR max; RPE 11-14 (6-20 scale) 3-5 d/wk for 20-60 min (or multiple 10-min sessions). | Perform one to three sets of 10-15 repetitions of 8-10 exercises involving the major muscle groups at 50%-80% of 1RM 2-3 d/wk. | Perform static stretches, holding 10-30 seconds 2-3 d/wk (before or after aerobic or strength training). | Perform tai chi, yoga, or recreational activities using paddles/sport balls to challenge hand-eye coordination. Active-play video and computer gaming counts too. Use as a complement to aerobic, muscle, and stretching activities 2-3 d/wk. |
| HRR = heart rate reserve; 1RM = 1 repetition maximum; RPE = rating of perceived exertion | |||
“If someone’s taking medication to prevent ongoing heart disease or recurrent stroke, combining that with physical activity and diet modifications can lead to a huge reduction in future events,” said Sandra Billinger, PhD, PT, vice chair of stroke translational research at the University of Kansas Medical Center in Kansas City, Kansas, and author of the AHA recommendations. (The 2014 paper says the risk for stroke recurrence can drop by as much as 80%.)
Note that the aerobic guidelines align with more moderate-intensity recommendations. More randomized controlled trials are needed to make firm recommendations regarding HIIT, according to Billinger.
Take Advantage of Local Resources
Having a support system can help keep patients motivated, and local physical activity programs can help.
The American Stroke Foundation offers a Next Step Program available in Kansas and Missouri that specifically helps stroke survivors get started with exercise. Participants can be active together, which Billinger said helps them develop a sense of community and cheer each other on. Local senior and community centers often have similar offerings, and the American Stroke Association website provides a database of stroke-support groups across the country.
“Exercise comes in a lot of forms,” said Billinger. “People think they have to pump iron and go to the gym, but there are a lot of ways to be physically active that benefit overall health.”
Start simple: Prescribe short walks, and let the person pick activities they enjoy so they will develop consistency.
Fleming said that prescribing exercise a person appreciates is also a good way to get them working out at higher intensities.
“In our facility, we have some people boxing,” Fleming said. (There is no full-contact sparring.) Boxing drills can be a kind of HIIT, and they work hand-eye coordination and muscle strength, in addition to making the participants feel empowered.
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