The Quantitative Assessment of Ankle Plantar Flexor Muscle Tone

ABSTRACT

OBJECTIVE: We designed this study to evaluate muscle tone by using a biomechanical method and to provide data for the future studies about muscle tone. METHOD: We evaluated 29 subjects without known neuromuscalar diseases using the biomechanical method. Both plantar flexors of each subject were passively stretched by isokinetic dynamometer from 30degrees plantar flexion position to 10degrees dorsiflexion position. Peak eccentric torque (PET) and torque threshold angle (TTA) were calculated at angular velocity of 10degrees/sec, 90degrees/sec and 300degrees/sec. Regression lines from torque/position curve at 10degrees/sec and 300degrees/sec were considered an intrinsic stiffness index (ISI) and total stiffness index (TSI). Stretch reflex threshold speed (SRTS) was defined as the minimum speed of plantar flexion movement in which EMG reflex activity in plantar flexor muscles is induced. RESULTS: The mean of TTA was higher in 10o/sec than in 300degrees/sec. The means of ISI and TSI were 0.11+/-0.08, and 0.18+/-0.04. The mean of SRTS was 125.2+/-48.3degrees. No statistical difference in each parameter was found according to the side or gender. CONCLUSION: ISI, TSI, PET, TTA and SRTS using a biomechanical method are thought to be useful parameters for the quantitative assessment of muscle tone change of ankle plantar flexors.