There is an urgent need to reduce the impact of stroke by promoting optimal rehabilitation strategies that decrease the risk of stroke. Improving cardiovascular health following a stroke is a key rehabilitation strategy that has the potential to reduce the risk of a recurrent event.

Adverse cardiovascular events, including stroke, are often due to chronic atherosclerosis, which shows as increased arterial stiffness. Elevated arterial stiffness is prevalent in individuals with cardiovascular disease, is associated with markers of silent cerebrovascular disease and is a new marker for predicting cardiovascular risk. Cardiopulmonary exercise tests (CPETs) are used to assess cardiorespiratory fitness. Novel CPET protocols have emerged for stroke, enabling safe and valid measurements of cardiorespiratory fitness. Cardiovascular exercise, typically performed through moderate-intensity continuous exercise (MICE), can improve function and fitness in individuals living with stroke and lower the risk of recurrent stroke. Recently, high-intensity interval exercise (HIIE) has emerged as a potentially potent stimulus that may also lead to improvements in function and fitness. While HIIE has shown benefits in clinical and non-clinical populations, only a few small, preliminary studies have examined the effects of HIIE in individuals living with stroke, and most have primarily focused on examining the effects of HIIE on function and gait. No study has examined and compared the acute effects of a CPET, MICE and HIIE on arterial stiffness in stroke. This study will (1) examine the acute effects of a single session of this HIIE protocol compared to a CPET and a single session of MICE on arterial stiffness among individuals with chronic stroke, and (2) the feasibility of a high-intensity interval training exercise protocol previously found to be tolerable and effective in attaining high levels of exercise intensity in in these individuals.

Stroke is the leading cause of adult disability and the fourth leading cause of death in Canada, with an annual cost to the economy of $3.6 billion. There is an urgent need to reduce the impact of stroke by promoting optimal rehabilitation strategies that decrease the risk of stroke. Improving cardiovascular health following a stroke is a key rehabilitation strategy that has the potential to reduce the risk of a recurrent event. Adverse cardiovascular events, including stroke, are often due to chronic atherosclerosis. Amplified arterial stiffness is a sign of atherosclerosis which increases arterial wall stress and reduces coronary perfusion. Elevated arterial stiffness is prevalent in individuals with cardiovascular disease, is associated with markers of silent cerebrovascular disease and is a new marker for predicting cardiovascular risk. Cardiopulmonary exercise tests (CPETs) are the gold standard for assessing cardiorespiratory fitness. In stroke, impairments in physical function may be present and limit individuals' ability to perform a CPET on traditional modes such as a cycle ergometer or treadmill. Thus, novel CPET protocols have been developed to allow individuals with stroke perform a fitness test safely and effectively. Cardiovascular exercise, typically performed through moderate-intensity continuous exercise (MICE), can improve function and fitness in individuals living with stroke and lower the risk of recurrent stroke. Recently, high-intensity interval exercise (HIIE) has emerged as a potentially potent stimulus that may also lead to improvements in function and fitness. HIIE combines short bursts of high-intensity cardiovascular exercise with periods of rest or recovery, and allows individuals to achieve higher intensities of cardiovascular exercise that do not need to be maintained for a long period of time like MICE. In this way, HIIE has the potential to be an additional exercise strategy to enhance cardiovascular health post-stroke. While HIIE has shown benefits in clinical and non-clinical populations, only a few small, preliminary studies have examined the effects of HIIE in individuals living with stroke, and most have primarily focused on examining the effects of HIIE on function and gait.

While the chronic effects of exercise on arterial stiffness have been examined in stroke, no study has examined the acute effects of a CPET, MICE, or HIIE. Different exercise stimuli may elicit variable short-term influences on arterial stiffness in individuals who have had a stroke, but this has not been previously examined. The feasibility of HIIE for individuals with a broader range of functional abilities after stroke is also not well established.

This study will (1) compare the acute effects of a HIIE session to a CPET and a session of MICE on arterial stiffness and (2) examine the feasibility of a HIIE protocol in individuals with a broad range of abilities after stroke. The investigators anticipate that (1) arterial stiffness will be elevated to a greater degree immediately following HIIE compared to the CPET and MICE, and will remain elevated following 15 minutes post-exercise, and (2) both HIIE and MICE protocols will be safe and feasible for individuals with stroke (no occurrence of adverse events), however the HIIE protocol will allow participants to obtain and be able to sustain a higher level of exercise intensity, and therefore a higher heart rate, compared to MICE. Understanding the time course of changes in arterial stiffness following acute exercise may provide insight into vascular responses of HIIE and thus potential underlying physiological mechanisms of post-stroke exercise.

Inclusion Criteria:

• 40-80 years of age
• >6 months following first-ever, single stroke
• Living in the community (not in an institutional setting)
• Able to walk at least 10 meters (assistive devices permitted)
• Able to follow commands.

Exclusion Criteria:

• Individuals will be excluded if they present with:
• Significant disability (a score >2 in the modified Rankin scale)
• Class C or D American Heart Association Risk Scores
• Any contraindications to exercise testing or training as set forth by the American College of Sports Medicine Guidelines for Exercise Testing and Prescription (ACSM, 2014)
• Any other neurological or musculoskeletal condition or co-morbidity that would preclude safe exercise participation
• Pain worsened with exercise
• Any cognitive, communication, or behavioral concerns that could limit safe exercise involvement