Stroke‐related effects on maximal dynamic hip flexor fatigability and functional implications

Abstract

Introduction Stroke-related changes in maximal dynamic hip flexor muscle fatigability may be more relevant functionally than isometric hip flexor fatigability. Methods Ten subjects with chronic stroke performed 5 sets of 30 hip flexion maximal dynamic voluntary contractions (MDVC). A maximal isometric voluntary contraction (MIVC) was performed before and after completion of the dynamic contractions. Both the paretic and non-paretic legs were tested. Results Reduction in hip flexion MDVC torque in the paretic leg (44.7%) was larger than the non-paretic leg (31.7%). The paretic leg had a larger reduction in rectus femoris EMG (28.9%) between the first and last set of MDVCs than the non-paretic leg (7.4%). Reduction in paretic leg MDVC torque was correlated with self-selected walking speed (r2=0.43), while reductions in MIVC torque were not (r2=0.11). Discussion Reductions in maximal dynamic torque of paretic hip flexors may be a better predictor of walking function than for maximal isometric contractions.

The Relevance of Sex Differences in Performance Fatigability

“…Fatigability can limit exercise performance, ergonomic tasks and daily activities, more so in older adults, those with chronic disease or disability such as stroke and multiple sclerosis [e.g. (56, 87). ] However, whether the sex differences in fatigability observed in healthy people are relevant to clinical populations is relatively unexplored, with some evidence for differences in people with multiples sclerosis and stroke.…”

“…This is especially true among clinical populations (56). Determining the relevance of the laboratory-based tasks and fatigability that limit both sexes in ergonomic tasks and daily activities will provide insight to offset potential injury and disorder in men and women.…”

Sex Differences in Neuromuscular Fatigability of the Knee Extensors Post-Stroke

“…In both men and women with stroke, recent evidence demonstrates that the limb muscles are more fatigable than healthy controls [ 6 , 7 ]. Fatigability can be quantified as the acute, exercise-induced reduction in maximal force or power of a muscle or the time to failure (task duration) of a submaximal intensity task [ 8 ].…”

“…Fatigability can be quantified as the acute, exercise-induced reduction in maximal force or power of a muscle or the time to failure (task duration) of a submaximal intensity task [ 8 ]. This greater neuromuscular fatigability with stroke compared with healthy controls was observed as a larger reduction in maximal dynamic voluntary contractions [ 6 ] and a reduced time to failure of sustained isometric contractions [ 7 ]. Accordingly, we have shown that fatigability of the hip flexor muscles is associated with walking speed in people with stroke [ 6 ], so that people with stroke who have greater hip flexion fatigability have larger decrements in walking performance [ 9 ].…”

“…This greater neuromuscular fatigability with stroke compared with healthy controls was observed as a larger reduction in maximal dynamic voluntary contractions [ 6 ] and a reduced time to failure of sustained isometric contractions [ 7 ]. Accordingly, we have shown that fatigability of the hip flexor muscles is associated with walking speed in people with stroke [ 6 ], so that people with stroke who have greater hip flexion fatigability have larger decrements in walking performance [ 9 ]. These results are consistent with clinical studies showing limited walking endurance [ 10 ] and low quality of movement [ 11 , 12 , 13 , 14 ] in people with stroke.…”