Assessment of torque-steadiness reliability at the ankle level in healthy young subjects: implications for cerebral palsy.

It was the primary objective of this study to investigate whether quantifying fluctuations in dorsi and plantarflexor torque during submaximal isometric contractions is a reliable measurement in young healthy subjects. A secondary objective was to investigate the reliability of the associated muscle activity (EMG) data. Eighteen young subjects (12.8 +/- 3.1 years, mean +/- 1 SD) were examined twice. At each visit, fluctuations in exerted torque (torque steadiness) and muscle activity from the tibialis anterior, gastrocnemius and soleus muscles were determined during submaximal isometric dorsi and plantarflexions. The relative reliability of the torque steadiness variables was substantial (0.80 < ICC(3.1) < 0.92), with an absolute reliability (average coefficient of variation) of 13-17%. The relative reliability of the muscle activity data was generally moderate (0.51 < ICC(3.1) < 0.90), with an absolute reliability of 6-26%. The reliability of dorsi and plantarflexion torque-steadiness measurements proved to be good in young healthy subjects.