The objective of this study is to examine the relationship between the spin-related variables during real four-seam fastball pitching in baseball and the finger force production capability and its coordination in the laboratory test. Consequently, the sets of variables were derived from two distinct experiments: a field task and a laboratory task. The field task was designed to quantify the spin-related variables during actual pitching performance, and the laboratory task was designed to quantify the strength of the two fingers and the coordination-related variables of the index and middle fingers during the cyclic net finger force production task. The statistical test was implemented with the primary objective of ascertaining the significant correlation between the two metrics from the field and laboratory tests. The findings indicated a negative correlation between finger forces and spin-related variables (p < .05), suggesting that those who have greater finger force do not have a positive effect on spin-related variables. The strength of the synergy indices of moment stabilization was associated with a positive effect on spin-related variables (p < .05). The present experiment demonstrated that the stabilization of mechanical variables by the force production of the two fingers, that is, the net moment, indicates that the rotational effect of finger force production plays a critical role in determining the superior spin qualities of a fastball pitch in baseball.
Keywords: force covariation; moment stabilization; spin-axis adjustment; uncontrolled manifold hypothesis.