Abstract TP66: Sex Differences In Neuromuscular Fatigability During Submaximal Isometric Knee Extension Exercise Post Stroke

Abstract

Introduction: Annually, 55,000 more females than males are affected by stroke in the United States. Females also tend to experience more severe strokes with worse functional outcomes, which result in poorer health-related quality of life. Despite the marked differences in long-term recovery between males and females with stroke, little is known about the sex differences in motor performance that may contribute to the differences in recovery and what therapies could be used to optimize recovery, especially for female stroke survivors. In this study, we aimed to determine if sex-related differences in neuromuscular fatigability exist post stroke. Methods: Sixteen chronic stroke survivors (at least 6 months post stroke, 9 females, 58 +/- 14 years) and thirteen neurologically intact controls (7 females, 59 +/- 12 years) performed a submaximal isometric fatiguing knee extension contraction with either the paretic (stroke) or the dominant (control) leg. The submaximal fatiguing contraction torque was equivalent to 30% of the maximal voluntary isometric contraction (MVIC) of the knee extensors. The participants were asked to sustain at the target torque until one of the two criteria for fatigue was met: (1) if the participant’s torque cannot maintain within a 10% window of error for more than 5 seconds; or (2) if there are more than 5 deviations from the 10% error window in a consecutive 10-second time period. Time to task failure (TTF) was measured. Results: Overall, both male and female stroke survivors tended to have lower MVIC than their healthy counterparts (male: 151 +/- 60 Nm vs. 206 +/- 39 Nm; female: 58 +/- 17 Nm vs. 121 +/- 27 Nm). On average, males tended to fatigue similarly between stroke and control groups (259 +/- 164 s vs. 249 +/- 96 s, respectively); while female stroke survivors tended to have a briefer TTF compared to female controls (207 +/- 69 s vs. 311 +/- 129 s). Conclusions: During submaximal isometric knee extension exercise, female stroke survivors had a shorter task duration than female controls, while this stroke-related difference was not observed in males. Our results indicate that, although stroke impairs muscle strength in both sexes, fatigability may be exacerbated to a greater extent in females than in males post stroke.