Effects of Arms and Countermovement on Vertical Jumping

摘要

Countermovement (C) and arm-swing (A) characterize most jumping. For determination of their effects and interaction, 18 males jumped for maximal height from a force platform four ways: C,A; C, no A; no C, A; no C, no A. For all jumps, vertical velocity peaked 0.03 sec before, and dropped 6-7% by takeoff. Peak positive power averaged over 3,000 W, and occurred about 0.07 s before takeoff, shortly after maximum vertical ground reaction force (VGRF) and just before peak vertical velocity. Both C and A significantly (p<0.05) improved jump height, but A's effect was greater, enhancing both height of the total body center of mass (TBCM) at takeoff and post-takeoff TBCM rise. C only affected the latter. Use of A resulted in less unweighting and slower descent of the TBCM during C, higher TBCM position at the bottom of C, higher peak VGRF, higher peak positive power, and lower negative power. C increased pretakeoff jump duration by 71-76%, increased average positive power, and resulted in large positive and negative impulses. Correlation of peak power with post-takeoff jump height was 0.88. Body weight and post-takeoff jump height effectively predicted peak power (r=0.94). The results lend insight into which jumping techniques are most appropriate for given sports situations. Keywords: Human power output; Force platform; Sport techniques; Stretch-shorten cycle; Impulse; Negative power.