What is the role of high-intensity interval training after a stroke?

This study looked at the effect of high-intensity interval training (HIIT) after a stroke. It found that HIIT improved walking distance, balance, and some parts of brain function in the short term.  

Exercise is known to be important for stroke recovery. HIIT involves repeated sessions of high-intensity effort followed by varied recovery times. It can use bodyweight, resistance bands, free weights, medicine balls, or weight machines. HIIT has been shown to be safe to perform after a stroke. However, it is not clear exactly what effect HIIT has on physical, mental, and cognitive (thinking and reasoning processes) recovery after stroke.

70 adult stroke survivors participated in this trial. Participants were 3 months to 5 years after the stroke. Participants were divided into two groups. Group 1 underwent HIIT training 3 times per week for 8 weeks. HIIT sessions consisted of 4 4-minute high-intensity exercises, separated by 3 minute periods of active rest. Group 2 received standard care only. A range of physical and cognitive tests was performed at the start, after 8 weeks, and again at a 12-month follow-up. 

After 8 weeks, the HIIT group showed a greater improvement in walking distance. This group walked an average of 28.3 meters further on a 6-minute walk test than group 2. The HIIT group also performed better on a balance test and on one of the cognitive tests than group 2. 

After 12 months, however, these differences were mostly lost. At 12 months the only area that the HIIT group scored better on was one of the cognitive tests, trail-making test B. This test involves planning and mental flexibility.

This study showed that HIIT leads to an initial improvement in walking distance, balance, and cognition after stroke compared to standard care. However, this difference was lost after 12 months. 

Patients involved in this trial were relatively young, and may not be representative of all stroke patients. Further studies are needed to see if these results apply to stroke patients generally.