S. Nadeau et al., Plantarflexor weakness as a limiting factor of gait speed in stroke subjects and the compensating role of hip flexors, CLIN BIOMEC, 14(2), 1999, pp. 125-135
Objective: To determine, using the Muscular Utilization Ratio (MUR) method,
whether plantarflexor weakness is among the factors preventing stroke subj
ects from walking at faster speeds. Potential compensations by the hip flex
ors were also examined.
Design: A convenience sample of 17 chronic stroke subjects in a context of
a descriptive study.
Background: Gait speed is correlated with the residual strength of the musc
les involved in gait in stroke subjects. However, it has not been establish
ed if this residual strength limits gait speed.
Methods: Kinetic and kinematic data for comfortable and maximal gait speeds
were collected on the paretic side, and were used to determine the moments
in plantarflexion (mechanical demand; MUR numerator) during the push-off p
hase. The maximal potential moment (MUR denominator) of the plantarflexors
during gait was predicted using an equation derived from dynamometric data
collected with a Biodex system. The MURs of the plantarflexors were then ca
lculated at every 1% interval of the push-off phase. The pull-off phase of
gait and the hip flexor strength were also examined.
Results: Ten subjects of the sample had a MUR value between 80 and 150% at
maximal gait speed. These subjects produced the lowest peak torques in plan
tarflexion. Each of the four fastest subjects of this group had a large hip
flexion moment during the pull-off phase of gait and produced high hip fle
xion torque values on the dynamometer. Each of the seven remaining subjects
had a MUR value under 70% when they walked at maximal speed.
Conclusions: Weakness of the plantarflexors should be considered as one fac
tor limiting gait speed in 10 hemiparetic subjects. Some subjects with weak
plantarflexors could walk rapidly because they compensated with the hip fl
exors. For the remaining stroke subjects, factors other than weakness of th
e plantarflexors have to be considered in order to explain the reduction in
their gait speed.