Fig. 5.
VH manipulation. a Normal forces of the thumb and VF versus the handle acceleration in the horizontal direction. A representative trial, the load was 11.3 N, the frequency was 3 Hz, representative subject no. 1. b Internal force and average normal force versus the handle acceleration. The range of the internal force fluctuations was approximately 8.0 N, from 12.0 to 21.0 N. c The thumb normal force–VF normal force phase angle [circular histogram, n=150 (six subjects × five loads × five frequencies)]