TASK-RELATED VARIATIONS IN MOTONEURONAL DRIVE TO A HUMAN INTRINSIC HAND MUSCLE

Maximal electromyogram (EMG) levels of the first dorsal interosseus mu scle (FDI) were studied during maximal pinching between index finger a nd thumb at two different wrist angles. Despite the fact that there wa s no change in the biomechanical conditions for the FDI, the maximal E MG levels of the FDI differed significantly; typically EMG levels were higher while pinching at a maximally flexed wrist angle compared to a maximally extended wrist angle. The stability of the EMG recordings w as checked with supramaximal peripheral nerve stimulation. Significant changes in the area of the compound muscle actions potentials (M-wave s) were obtained. However, these changes could not explain the observe d differences in the maximal EMG levels. Our results suggest that the ease of producing a maximal drive to the FDI muscle depends on the mot or task. (C) 1998 Elsevier Science Ireland Ltd.