Mechanical energetics of post-stroke hemiparetic gait
Date
2011
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Publisher
University of Delaware
Abstract
Stroke is the third leading cause of death in the United States. Survivors are often left with residual muscle weakness and spasticity that lead to slower self-selected walking speeds and increased metabolic energy expenditure when compared to their healthy peers. They also exhibit asymmetric movement patterns and compensatory strategies which may adversely affect mechanical work production. Objective: This study examined the effect of speed modulation on mechanical work production and mechanical recovery in post-stroke gait. It also investigated the ability of post-stroke kinematics and kinetics to predict which stroke survivors have the capacity to increase their mechanical recovery. Ten chronic stroke survivors and 6 healthy young adults were recruited for this study. Kinematic data were collected while all subjects walked on an instrumented split-belt treadmill at speeds slower and faster than their self-selected speed. Internal work, external work, mechanical recovery, circumduction, swing asymmetry, paretic ankle and hip work, peak knee flexion during swing, peak hip extension, and paretic leg kinetic energy at toe-off were measured or calculated. Spearman rank correlation analysis was used to detect significant relationships among all gait variables of interest. Wilcoxon signed rank tests were used to detect individual changes in gait variables across the ranges of increasing and decreasing mechanical recovery. Mechanical recovery exhibited a parabolic relationship with walking speed in healthy adults with peak recovery occurring near self-selected walking speed. Mechanical recovery improved in most stroke subjects at walking speeds up to 1 m/s. Increased mechanical recovery was also accompanied by increased peak knee flexion, paretic ankle work, and paretic leg kinetic energy. Only paretic leg kinetic energy was able to predict mechanical recovery post-stroke. Internal work production in the frontal plane increased linearly with walking speed in healthy adults, but not in stroke survivors. Speed modulation up to 1 m/s is critical for achieving optimal mechanical recovery in stroke survivors. Stroke survivors with the slowest self-selected walking speeds benefit most from speed modulation regardless of the strategies they employ to clear the paretic limb during swing. The use of compensation strategies may actually be beneficial because they allow faster walking speeds to be attained without significantly increasing mechanical work production.