Jr. Flanagan et Am. Wing, MODULATION OF GRIP FORCE WITH LOAD FORCE DURING POINT-TO-POINT ARM MOVEMENTS, Experimental Brain Research, 95(1), 1993, pp. 131-143
In this paper, we examine grip forces and load forces during point-to-
point arm movements with objects grasped with a precision grip. We dem
onstrate that grip force is finely modulated with load force. Variatio
ns in load force arise from inertial forces related to movement; grip
force rises as the load force increases and falls as load force decrea
ses. The same finding is observed in vertical and horizontal movements
performed at various rates. In vertical movements, maximum grip force
coincides in time with maximum load force. The maxima occur early in
upward and later in downward movements. In horizontal movements, where
peaks in load force are observed during both the acceleratory and dec
eleratory phases, grip force rises at the beginning of the movement an
d remains high until the end. The results suggest that when moving an
object with the hand the programming of grip force is an integral part
of the planning process.