Journal
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY
Volume 88, Issue 6, Pages 558-564Publisher
SPRINGER
DOI: 10.1007/s00421-002-0748-4
Keywords
ankle instability; delay; electrical stimulation; electromechanical; peroneus longus muscle; stance
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The goal of this study was to approach ankle instability by measuring the electromechanical delay of the peroneal muscles (foot pronators). For that purpose, supramaximal electrical stimulation of common peroneal nerve was applied when the subject was standing on a force plate in bipedal stance or monopedal stance, postures requiring greater ankle stabilization. The electromechanical delay (EMD) was defined as the time interval between the onset of the peroneus longus (PL) electromyogram detected by surface electrodes and the onset of the lateral ground reaction force (Fy) measured on a force plate. Ten healthy subjects (control group, C-G) and ten subjects with functional ankle instability (FAI group, FAI-G) performed the tests. In C-G, the mean EMD values decreased significantly (P < 0.001) from the bipedal [10.54 (0.71) ms; mean (SD)] to the monopedal stance [8.67 (0.63 ms)]. Since a monopedal stance is known to require higher leg muscle tone resulting in a higher ankle stiffness, these results indicate that PL EMDs are sensitive to musculo-tendinous stiffness. They validate the choice of a PL EMD measurement as an indirect index of musculo-tendinous stiffness at the ankle. In both bipedal and monopedal stance conditions, EMD values were significantly higher in FAI subjects. They ranged from 12.64 (1.14) ms in the bipedal stance to 10.85 (1.07) ins in the monopedal stance. This suggests a lower musculo-tendinous stiffness at the ankle, which may contribute to the ankle instability.
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