Two methods for the measurement of voluntary contraction torque in the biceps brachii muscle

Appropriate measurement of maximal voluntary contraction force of a single limb muscle or of a muscle group is important in clinical and research situ ations. To measure muscle force, one segment of an isometric measuring brac e is fixed to a support and force is applied to the other. The output of th is arrangement is affected by additional contributions such as pushing or p ulling with the whole body. This paper quantifies the differences between m easurements of torque produced by the biceps brachii with the brace fixed v ersus those produced when the elbow joint was isolated by suspending the br ace from cables. No statistically significant differences were found between MVC values obse rved with the two methods within subjects. However, a statistically signifi cant difference in EMG fatigue indices was observed and attributed to a dif ferent sharing of force production among different muscles in the two condi tions. We conclude that different brace arrangements may lead to the same maximal force but to different rates of myoelectric manifestations of muscle fatigu e since the effort may be shared differently among the muscles of synergic or stabilizing groups. (C) 1999 IPEM, Published by Elsevier Science Ltd. Al l rights reserved.