Stroke-Related Changes in Neuromuscular Fatigue of the Hip Flexors and Functional Implications

Allison Hyngstrom, Marquette University
Tanya Onushko, Marquette University
Robert Heitz, Marquette University
Anthony Rutkowski, Georgia Institute of Technology - Main Campus
Sandra Hunter, Marquette University
Brian Schmit, Marquette University

American Journal of Physical Medicine & Rehabilitation, Vol. 91, No. 1 (January, 2012): 33-42. Permalink. © 2012 Lippincott Williams & Wilkins, Inc.


Objective: The aim of this study was to compare stroke-related changes in hip flexor neuromuscular fatigue of the paretic leg during a sustained isometric submaximal contraction with those of the nonparetic leg and controls and to correlate fatigue with clinical measures of function.

Design: Hip torques were measured during a fatiguing hip flexion contraction at 20% of the hip flexion maximal voluntary contraction in the paretic and nonparetic legs of 13 people with chronic stroke and 10 age-matched controls. In addition, the participants with stroke performed a fatiguing contraction of the paretic leg at the absolute torque equivalent to 20% maximal voluntary contraction of the nonparetic leg and were tested for self-selected walking speed (10-m Walk Test) and balance (Berg).

Results: When matching the nonparetic target torque, the paretic hip flexors had a shorter time to task failure compared with the nonparetic leg and controls (P < 0.05). The time to failure of the paretic leg was inversely correlated with the reduction of hip flexion maximal voluntary contraction torque. Self-selected walking speed was correlated with declines in torque and steadiness. Berg-Balance scores were inversely correlated with the force fluctuation amplitude.

Conclusions: Fatigue and precision of contraction are correlated with walking function and balance after stroke.