Coordination of the non-paretic leg during hemiparetic gait: Expected and novel compensatory patterns

Abstract

Background Post-stroke hemiparesis is usually considered a unilateral motor control deficit of the paretic leg, while the non-paretic leg is assumed to compensate for paretic leg impairments and have minimal to no deficits. While the non-paretic leg EMG patterns are clearly altered, how the non-paretic leg acts to compensate remains to be established. Methods Kinesiological data were recorded from sixty individuals with chronic hemiparesis (age: 60.9, S.D. =12.6 years, 21 females, 28 right hemiparetic, time since stroke: 4.5 years, S.D. 3.9 years), divided into three speed-based groups, and twenty similarly aged healthy individuals (age: 65.1, S.D. =10.4 years, 15 females). All walked on an instrumented split-belt treadmill at their self-selected speed and control subjects also walked at slower speeds matching those of the persons with hemiparesis. We determined the differences in magnitude and timing of non-paretic EMG activity relative to healthy control subjects in four pre-defined regions of stance phase of the gait cycle. Findings Integrated EMG activity and EMG timing in the non-paretic leg were different in many muscles. Multiple compensatory patterns identified included: increased EMG output when the muscle was typically active in controls and novel compensatory EMG patterns that appeared to provide greater propulsion or support with little evidence of impaired motor performance. Interpretation Most novel compensations were made possible by altered kinematics of the paretic and non-paretic leg (i.e., early stance plantarflexor activity provided propulsion due to the decreased advancement of the non-paretic foot) while others (late single limb stance knee extensor and late stance hamstring activity) appeared to be available mechanisms for increasing propulsion.

Forward propulsion asymmetry is indicative of changes in plantarflexor coordination during walking in individuals with post-stroke hemiparesis

“…In non-impaired walking the hamstrings are typically active only into early stance, and therefore do not generate propulsion during late stance (Neptune et al, 2004). Prolonged activity of both the paretic (Den Otter et al, 2007; Knutsson and Richards, 1979) and nonparetic (Raja et al, 2012) hamstrings later into stance has previously been documented post-stroke. This prolonged duration may represent a compensatory mechanism to overcome plantarflexor weakness that does not appear related to PP.…”

A novel fMRI paradigm suggests that pedaling-related brain activation is altered after stroke

“…Tests of these hypotheses are forthcoming from our lab with fMRI studies comparing brain activation post-stroke during unilateral pedaling and bilateral pedaling without mechanical coupling of the two legs. Results may have important implications for rehabilitation of hemiparetic walking, as reduced use of the paretic leg also occurs during walking ( Allen et al, 2011 ; Raja et al, 2012 ).…”

Prevention of Genu Recurvatum in Poststroke Patients Using a Hinged Soft Knee Orthosis

“…In the example depicted in Figure 3, the subject exhibited close to normal muscle activity in the nonparetic limb, except in his semitendinosus muscle, which was not activated during initial contact and the loading phase of the gait cycle. Although observation of abnormal muscle activities in the paretic leg is expected, muscle activation patterns of the nonparetic leg may also display some abnormalities [34‐36]. The rectus femoris activity in the paretic limb during the stance phase was slightly increased when walking with the orthosis and closer to the normal activity pattern.…”