HOW THE BODY WEIGHT AFFECT THE PULLING FORCE IN HAMMER THROW?

Abstract

RESULTS AND DISCUSSION Table 1 shows the results for typical 2 throwers. Their performances were almost the same (0.4%) although their body weights were quite different (24%). Throwing distance and initial velocities were similar in two throwers. However, maximum pulling forces per body weight were quite different. Therefore the relationship between the pulling force and body weight should be examined in detail. The hammer throwing motion can be compared with two-body problem in mechanics between a thrower’s body and a hammer head. Therefore, it can be considered that body and hammer head rotate each other around the common center of gravity of these two bodies. In this study, the body weight of thrower-B was larger than that of thrower-A about 24%. Then radius of gyration from the common center of gravity to hammer head in thrower-B was longer than in thrower-A. As the velocity of the hammer head at release were almost the same in two throwers, maximum pulling force of thrower-A was larger than that of thrower-B because the centrifugal force (= the maximum pulling force) was inversely proportional to the radius of gyration. Fig.1 shows relationship between throwing distance and maximum pulling force for all the throwers. Thrower's body weight was shown in frames. The multiple linear regression analysis was done by choosing MPF as dependent variable and throwing distance and body weight as independent variables. Figure 1: Relationship between throwing distance and maximum pulling force.