Figure 7.

Relations between the external torque generated by the suspended load (abscissa) and the moment produced by the normal forces of the fingers, Mⁿ (ordinate). Group average data are shown (n=10). The data are for four different loads. The coefficients of the regression equations Mⁿ =a+b(Torque) are: for load 0.5 kg, slope b=0.451, intercept a = 0.06; load 1.0 kg, b=0.473, a = 0.02; load 1.5 kg, b=0.492, a = −0.01; load 2.0 kg, b=0.504, a = −0.01. Note that the intercepts are very small; hence the regression lines pass very close to the origin of the system of coordinates. Consequently, the percentage contribution of Mⁿ into the total moment exerted on the object by the performers remains constant. Since the sum Mⁿ + M^t equals the total moment, the percentage contribution of Mⁿ into the total moment is also invariant. (Adapted by permission from V.M. Zatsiorsky, R.W. Gregory, and M.L. Latash. Force and torque production in static multifinger prehension: biomechanics and control. I. Biomechanics. Biological Cybernetics, 2002, 87:50–57.)