Feasibility Study to Increase Resilience Through an At-home Virtual Exercise Training (Res-ET) Intervention Using Inspiratory Muscle Strength Training (IMST)

Strokes impact a growing number of younger individuals; it has been reported that approximately 10 to15% of all strokes occur in individuals 18 to 50 years of age with hospitalization rates almost doubling from 1995 to 2012. Disability or the onset of a chronic condition like stroke is often life-altering and this might be exaggerated in persons who have a stroke at a younger age at the height of managing family and work responsibilities. The FUTURE study reports after a 13.9 year follow up that 44.7% of young stroke patients have poor functional outcomes. Young stroke survivors may encounter lifelong challenges impacting physical, emotional, visual, and cognitive capabilities. Edwards and colleagues (2019) reported young stroke survivors with no early recurrence showed a 7-fold increased hazard ratio of long-term risk of adverse outcomes when compared to young healthy controls. Post-stroke depression affects approximately one third of all stroke survivors and young stroke survivors are nearly three times more likely to have anxiety and depression. Current focus in rehabilitation is on acute physical and neurological function and integration, but this focus may not necessarily lead to positive long-term outcomes for young stroke survivors.

Resilience is the inherent and acquired ability to recover and sustain a new way of thriving after a life altering event or situation. Resilience has been shown to be dependent on inherent and acquired factors that have both modifiable and non-modifiable components. Understanding the relationship between resilience and disability is still new but it appears increased resilience may mitigate secondary symptoms such as pain or fatigue, may predict physical functioning, is positively associated to self-efficacy, optimism, and improved quality of life. According to Terrill et al.'s (2019) Resilience and Disability model, resilience is dependent on intrapersonal, social-environmental, and interpersonal factors that dynamically influence an individual's capacity to achieve and maintain quality of life and well-being. Interactional aspects of intrapersonal and environmental factors influence relationships, systems of support, and combine to create an ecosystem for resilience and well-being. Increasing/modifying psychosocial components related to intrapersonal, intrapersonal, and environmental factors have been shown to increase resilience such as; self-efficacy, positive affect, positive psychological well-being, meaning and purpose, and engagement with social environment.

Exercise may be a potential mechanism for enhancing resilience. For example, Childs and Wit (2014) found that regular exercise is associated with psychosocial factors like emotional resilience to acute stress in healthy adults and Deuster and Silverman (2013) proposed a conceptual model where increased levels of fitness link to increased resilience. Evidence also suggests that exercise need not be intensely physically demanding to enhance mental and emotional health. The positive effects of low-intensity physical movement programs on resilience have not been examined in the young stroke survivors. Exercise has been significantly associated with improved self-reported mental health and preliminary findings demonstrated exercise improves mental health outcomes after stroke, but empirical studies examining these effects are still largely lacking, especially in young stroke survivors who are at greater risk of depression and distress.

Exercise is a commonly prescribed treatment post-stroke, and benefits derived through exercise may parallel those identified in the Resilience and Disability model. Exercise interventions have the potential to positively influence multiple psychological, physical, and psychosocial domains after stroke. Exercise is typically defined as any bodily movement produced by skeletal muscles that results in energy expenditure, and is planned, structured, and repetitive with a final or an intermediate objective of improvement or maintenance of physical fitness. There is strong evidence that exercise after stroke can improve cardiovascular fitness, walking ability, and upper-extremity muscle strength. There is also evidence that exercise has positive effects on depression and cognition in adults without stroke, and preliminary findings demonstrate that exercise may confer similar effects after stroke. Although the benefits of regular exercise are well established there is reported low patient adherence and motivation for implementation among stroke survivors.

Inspiratory muscle strength training (IMST) consists of performing repeated inspirations against resistance with unopposed expirations and uses the diaphragm and accessory muscles to repeatedly inhale against resistance. IMST is performed using either a constant resistance or a pressure-threshold device. Airflow through pressure-threshold devices is regulated by a valve that fully occludes airflow until a prescribed threshold is exceeded, at which point the valve opens to allow airflow. IMST requires the user to develop inspiratory pressures that are significantly greater than those produced during tidal breathing and may be similar to inspiratory pressures produced during high intensity aerobic exercise. Although IMST is not new, novel insights on potential mechanisms for physiological adaptation are promising. IMST has been shown to increase respiratory muscle strength, decrease blood pressure, increase endothelial function, reduce systemic inflammation, reduce heart rate at rest, improve heart rate variability, and during exercise, improve exercise capacity and endurance. IMST has been shown to lead to physiological adaptation in a wide range of populations and has been identified effective in stroke survivors. In a recent systematic review on respiratory muscle training, Pozuelo-Carrascosa et al. identified multiple studies that demonstrated increases in pulmonary function, maximal inspiratory pressure, and walking ability. IMST exercise prescription for frequency and intensity on stroke populations are still being explored and have been used in a wide range of frequencies ranging from 3 times p/week up to 7 times p/week and intensities usually expressed in a percentage of maximal inspiratory pressure (MIP) ranging from 30% of MIP to 75% of MIP, for durations usually expressed in number of breaths or time under tension 5 min (30 breaths) p/session to 60 min (100+ breaths) p/session. IMST has the potential to enhance physical health and resilience in young stroke survivors.