Modulation of balance recovery responses to walking trip perturbations in people with chronic stroke - More than six months after a stroke people are 2.5 times more likely to fall compared to their healthy peers. A third of all reported falls occur when people with stroke trip while walking around their home and in their community. Falls may result in devastating injuries like hip fractures that interfere with their activities of daily living needed to maintain their health and well-being. This limits how physically active people with stroke can be and shortens their lifespan. These falls occur despite physical therapists teaching people how to maintain their balance and walk again after a stroke. Usually exercises for people with stroke focus on regaining function as quickly as possible so that they can return home. This involves using specific tasks that train general movement patterns needed to perform daily activities rather than exercising specific muscles. The assumption is that muscles will improve through general movement, which is true to an extent. Not exercising specific muscles limits the amount of improvement observed in people with stroke. Thus, even 6 months after a stroke, and even after going through a stroke recovery exercise program, people with stroke still rely on alternative movements while performing daily tasks like walking, to compensate for reduced muscle performance. Thus, even though people with stroke may be able to successfully maintain their balance, they are still at risk of falling. There is limited information regarding which muscles specifically help prevent falls after a trip while walking. In this study we decided to start by examining the muscle in front of the ankle, the Tibialis Anterior, since it is responsible for helping the foot clear the ground, thus preventing a trip while walking. The Tibialis Anterior muscle may be weaker after a stroke, with 20%-30% of people with stroke only able to use it minimally, if at all, requiring the long-term use of an ankle brace while standing and walking. The first objective of this study is to examine how quickly and how active the Tibialis Anterior muscle becomes when people are trying to recover their balance after a trip while walking. We also want to examine whether the Tibialis Anterior muscle can modulate its level of activity in response to trips of lower or higher intensities. Responses in people with stroke will be compared to healthy controls of similar age and sex. The second objective of this study is to examine whether factors like the time to reach peak Tibialis Anterior muscle oxygen usage while walking and individual physical activity status affect the rate of Tibialis Anterior muscle activity during balance recovery. If these factors affect Tibialis Anterior muscle activity, then this provides physical therapists with a way to not only improve muscle performance during balance recovery but also prevent a fall after a trip while walking. We will also report whether there are differences in the amount of time needed to reach peak Tibialis Anterior muscle oxygen levels while walking by people with stroke compared to healthy controls of similar age and sex. We will also identify differences in how physically active people with stroke are compared to healthy controls of similar age and sex. Individual physical activity status is defined by the number of steps taken per day, the intensity of daily physical activity and the amount of time spent sitting and lying down, other than sleeping. The result of this study lays the foundation for future research that focuses on the development of muscle specific exercise recommendations that target fall prevention and not just a general improvement in balance.
