THE ORGANIZATION OF MULTISEGMENTAL PULLS MADE BY STANDING HUMANS .2. SUBMAXIMAL PULLS

Previously, an autonomous oscillator model with three parameters was d erived that describes the relationship between anterior-posterior cent er of mass motions and pulling force for near-maximal, bimanual pulls made by standing subjects (Michaels, Lee, & Pai, 1993). The present st udy evaluated the extent to which a full range of pulling forces could be fit by the model and how the model's three parameters changed with intended pulling force. How much variation in force each parameter co uld contribute was determined by simulating the model. Qualitative and quantitative analyses of pulls made by 6 well-practiced subjects at 5 %, 10%, 20%, 40%, 60%, 80%, and 95% of their maximum pulling force rev ealed that the model holds well, except for the least forceful pulls o f some subjects. Two parameters appeared to be controlled; one, relate d to the position of the center of pressure, varied most among less fo rceful pulls; the second, related to the position of the center of mas s at the time of handle-force onset, varied most among more forceful p ulls. How these parameters might be set is discussed.