Cf. Michaels et Wa. Lee, THE ORGANIZATION OF MULTISEGMENTAL PULLS MADE BY STANDING HUMANS .2. SUBMAXIMAL PULLS, Journal of motor behavior, 28(2), 1996, pp. 137-148
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.