Dynamometric assessment of the plantarflexors in hemiparetic subjects: relations between muscular, gait and clinical parameters

The aims of this study were to investigate, in 16 subjects with hemiparesis, the plantarflexor muscle performance of the paretic side and to determine the level of the relationships between muscular parameters, clinical measures and gait performance. A Biodex dynamometric system was used to evaluate static and dynamic torques, power and maximal rate of tension development of the plantarflexor muscles. The clinical measures included the Fugl-Meyer assessment (FMA), the "Up & Go" test and an evaluation of ankle muscle tone. Velocity, cadence, stride length and gait cycle duration were determined for each subject at both comfortable and maximal safe speeds using foot contacts and videographic data. Results indicated that dynamometric values produced by the hemiparetic subjects were reduced in comparison to those reported for healthy subjects. Their torque-angle curves had a curvilinear shape which indicated pronounced decrease of torque for plantarflexion efforts at the beginning of the movement. Torques produced at different velocities of testing did not demonstrate significant differences (MANOVAs: p > 0.05) but power values were significantly different. Results also showed that all the selected muscular parameters (torque, power and maximal rate of tension development) were moderately to highly interrelated (0.65 < r < 0.94; p < 0.01) suggesting that a common factor of muscular performance was assessed. Furthermore, the dynamometric data were significantly associated with some of the clinical measures (sensation and lower limb motor control scores of the FMA) but were not related to the gait variables (Pearson's r < 0.45; p > 0.05). This last finding suggests that the relationship between plantarflexor strength and the level of gait performance in adults with stroke is complex. The relationship may be influenced by other factors such as muscular compensations within and between limbs and motor control impairments.