1st Joint ESMAC-GCMAS Meeting - Análise de Marcha

variability was larger (p < .001) for the hemiplegics (53ms) than for the control participants
(15ms).
For trials with clear frequency coupling (| ∆f| < 0.05), the variability of the relative phase between
ipsilateral instants of auditory pacing and heel strikes σ for the left and right side were compared.
In the control group variability of relative phase did not differ significantly between the left
(7.3°) and right (7.1°) side of the body, whereas in the hemiplegic group σ was significantly (p <
.05)lower for the non-paretic side (9.5°) than for the paretic side (11.7°).
Figure 1. Spectrograms; contribution of frequency
components is proportional to the brightness.
Discussion
The analysis of auditory-motor coordination showed that in stroke patients the relative phase
variability between ipsilateral pacing signals and heel strikes σ was significantly lower for the
non-paretic side than for the paretic side. In general, local decrease of variability may indicate
points or regions in the workspace where useful task-specific information is available, such as
information about the required timing [3]. Given such ‘anchoring’ [3], it may be postulated that
stroke patients coordinate their gait to the perceptual stimulus by predominantly controlling (i.e.,
synchronizing, timing) the movements of the non-paretic body side to the ipsilateral pacing
stimulus. Apparently, this is the most efficient way to deal with their gait asymmetry in this
perceptual-motor task (i.e., paced walking). In the control group, no indications for lateralized
auditory-motor anchoring were observed. These results substantiate the suggestion by Wagenaar
and Beek [2] that tweaking the perception-action coupling by means of external rhythms can
improve the spatiotemporal organization of pathological gait. Interestingly, from these
observations new rehabilitation strategies might be distilled. For example, instructing
hemiplegics to couple the heel strikes of their paretic instead of their non-paretic leg to the pacing
signal might tentatively lead to improved gait coordination by increasing step length of the
paretic limb.
References
[1] Wagenaar RC, Beek WJ (1992). Hemiplegic gait: a kinematic analysis using walking speed as a basis. Journal of
Biomechanics, 25, 1007-1015
[2] Thaut MH, McIntosh GC, Rice RR (1997). Rhythmic facilitation of gait training in hemiparetic stroke
rehabilitation. Journal of the Neurological Sciences, 151:207-212.
[3] Beek PJ (1989). Juggling dynamics. Free University Press, Amsterdam
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