Abstract
Background.
High-intensity, variable stepping training can improve walking speed in
individuals poststroke, although neuromuscular strategies used to
achieve faster speeds are unclear. We evaluated changes in joint
kinetics and neuromuscular coordination following such training;
movement strategies consistent with intact individuals were considered
evidence of recovery and abnormal strategies indicative of compensation.
Methods. A total of 15 individuals with stroke (duration: 23 ±
30 months) received ≤40 sessions of high-intensity stepping in variable
contexts (tasks and environments). Lower-extremity kinetics and
electromyographic (EMG) activity were collected prior to (BSL) and
following (POST) training at peak treadmill speeds and speeds matched to
peak BSL (MATCH). Primary measures included positive (concentric) joint
and total limb powers, measures of interlimb (paretic/nonparetic
powers) and intralimb compensation (hip/ankle or knee/ankle powers), and
muscle synergies calculated using nonnegative matrix factorization.
Results.
Gains in most positive paretic and nonparetic joint powers were
observed at higher speeds at POST, with decreased interlimb compensation
and limited changes in intralimb compensation. There were very few
differences in kinetic measures between BSL to MATCH conditions.
However, the number of neuromuscular synergies increased significantly
following training at both POST and MATCH conditions, indicating gains
from training rather than altered speeds. Despite these results, speed
improvements were associated primarily with changes in nonparetic versus
paretic powers. Conclusion. Gains in locomotor function were
accomplished by movement strategies consistent with both recovery and
compensation. These and other data indicate that both strategies may be
necessary to maximize walking function in patients poststroke.
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