Reactive Balance Training and Fitness

People with stroke should exercise to maintain function and reduce the risk of another stroke. Different types of exercise target different components of fitness, such as aerobic, strength, and balance. Post-stroke exercise guidelines exist for each type of exercise separately (eg, brisk walking as aerobic exercise, resistance training for strength, and Tai Chi for balance). Meeting these recommendations means spending a lot of time exercising, and people with stroke say that lack of time and fatigue are barriers to exercise. It is possible to target several components of fitness with one type of exercise.

'Reactive balance training' (RBT) is a type of exercise that improves control of reactions that are needed to prevent a fall after losing balance, and is the only type of exercise with potential to prevent falls in daily life post-stroke. Because RBT involves repeated whole-body movements it may have similar aerobic benefit as other exercises using whole-body movements (eg, brisk walking). Also, leg muscles need to generate a lot of force to make rapid steps in RBT; repeatedly generating this force may help to improve strength.

The purpose of this study is to determine if RBT improves two important components of fitness among people with chronic stroke: aerobic capacity and strength. The investigators expect that the improvements in aerobic capacity and strength after RBT will not be any worse than after an exercise program that specifically targets aerobic fitness and strength. A secondary purpose of this study is to determine the effects of RBT compared to aerobic and strength training on balance control and balance confidence. The investigators expect that RBT will lead to greater improvements in balance control and balance confidence than an aerobic and strength training program.

This is an assessor-blind randomized non-inferiority trial with an internal pilot study. Research activities will take place at the Toronto Rehabilitation Institute and the University of Toronto. For the internal pilot study, we will initially recruit 20 participants with chronic stroke and randomly assign them to one of two groups: 1) RBT, or 2) AST. Cardiorespiratory fitness, lower-extremity strength, balance control, and balance confidence will be measured pre- and post-intervention. We will calculate the final target sample size using the variability observed in this internal pilot. Additionally, a Trial Steering Committee will determine the criteria for the progression from the internal pilot to the main study, and will decide on the continuation of the internal pilot with or without modifications based on those pre-defined criteria (e.g., criteria based on feasibility or preliminary evidence of effect of the interventions from examination of effect sizes).

Eligibility Criteria:
Inclusion Criteria:

* Community-dwelling adults with chronic stroke (\>6 months post-stroke).
* Able to stand independently without upper-limb support for \>30 seconds.
* Able to tolerate at least 10 postural perturbations while wearing a safety harness.

Exclusion Criteria:

* \>2.1m tall and/or weighing \>150kg (limits of the safety harness system).
* Other neurological condition that could affect balance control (e.g., Parkinson's disease).
* Lower extremity amputation.
* Cognitive, language or communication impairments affecting understanding instructions.
* Recent (last 6 months) significant illness, injury or surgery.
* Severe osteoporosis, defined by diagnosis of osteoporosis with fracture.
* Severe uncontrolled hypertension, or uncontrolled diabetes.
* Contraindications to exercise testing, such as symptomatic aortic stenosis, complex life-threatening arrhythmias, unstable angina, or orthostatic blood pressure decrease of \>20 mmHg with symptoms.
* Acute or chronic illness or injury likely to be exacerbated by exercise (e.g., recent lower-extremity fracture).
* Currently attending in- or out-patient physiotherapy, in which they receive aerobic training, balance training or strength training for lower limb.
* Significant exercise participation: current physical activity levels that meet the recommended guidelines (at least 150 minutes of moderate-to-vigorous or at least 75 minutes of vigorous physical activity/week) as calculated using the moderate and vigorous components of the Leisure Time Exercise Questionnaire (LTEQ) in the month prior to starting the study.
* Received perturbation training at Toronto Rehab \<1 year previously.