Aerobic conditioning is very important after stroke as it may reduce the risk of subsequent stroke and overall mortality. High-intensity interval training (HIIT), in which aerobic training workload is varied between lower and higher intensity bouts within a training session, is known to be effective for maximizing aerobic capacity in healthy individuals and those with cardiac disease. HIIT has not been studied extensively in adults with stroke, but it could be an efficient way to maximize aerobic capacity in this population. Furthermore, using heart rate response to establish training intensity may lead to underestimation of target intensity after stroke because blood pressure medications may blunt the heart rate response. Ventilatory threshold is an alternate method of establishing training intensity and is derived independently of heart rate response. The investigators hypothesized that a 10-week program of treadmill HIIT with intensity based on ventilatory threshold would be feasible in adults at least 6 months post-stroke, and would increase aerobic capacity.

Stroke is the main cause of serious, long-term disability among Americans. The effects of a stroke make it difficult to participate in routine, daily activities so people become seriously deconditioned after a stroke. This increases the chances of having another stroke and it also increases the risk of death. Even a small increase in aerobic capacity reduces these risks, making aerobic training an important component of post-stroke management.

Twenty to 60 minutes of moderate-intensity exercise on most days of the week is recommended for people with cardiovascular disease, but this is not very practical for many people after a stroke, who need to practice functional tasks like using the impaired arm and improving walking and balance. Another problem is that even when people do participate in aerobic training after a stroke, the improvements in aerobic capacity are sometimes surprisingly small. It is possible that the intensity of the training program was inadequate to improve aerobic capacity in some interventions. High-intensity interval training, in which people alternate between short, intense bouts of exercise and recovery bouts within the session, may be a way to improve aerobic capacity after a stroke with a more feasible training schedule that leaves time to practice functional skills too. High-intensity interval training on a treadmill might be appropriate to improve aerobic capacity and walking ability.

This non-randomized, non-blinded pilot study was designed to assess the feasibility of ten weeks of high-intensity interval training (HIIT) using treadmill training for adults with impaired walking who were at least 6 months post-stroke.

A secondary objective was to measure change in aerobic capacity, and a tertiary objective was to measure functional change in self-selected walking speed and leg strength as a result of the intervention.

10 participants completed HIIT intervention while 5 participants served as controls and received no intervention, but completed both baseline and post-testing sessions.

HIIT participants completed twice-weekly, 35-minute training sessions in a research laboratory for 10 consecutive weeks. At baseline and 12 weeks, all participants completed a graded exercise test, 10-meter walk test at self-selected and fastest, safe overground walking speeds, and a 30-second sit-to-stand test.

Inclusion Criteria:

• Male and female adults 18 years of age or older who had a unilateral stroke at least 6 months prior to enrollment
• Ability to provide informed consent and follow instructions to participate
• Medically stable
• Must be able to walk with no more than contact guard assistance on level surfaces
• Must be willing to walk on a treadmill with a support harness and handrail

Exclusion Criteria:

• Cerebellar stroke
• Medical instability
• Implanted pacemaker or defibrillator
• Inability to walk on a treadmill with a support harness and use of handrail for at least 5 minutes
• Absence of walking impairments
• Abnormal resting heart rate, blood pressure or ECG
• Abnormal ECG during graded exercise test