| Description |
The primary aim of the current study was to examine the influence of peak pelvictorso separation angle (PPTSA), peak upper torso rotational velocity (PUTRV), and peak pelvic rotational velocity (PPRV), on spiked ball velocity (SBV) during both down-theline (DL) and diagonally across-court (DAC) spikes. The second aim was to establish reliability and validity evidence for the core trainer (CT) as a measure of PPTSA, PUTRV, and PPRV during volleyball spiking actions. Voluntary participants were 14 collegiate, Division I, female volleyball players from the University of Utah, ranging from 18-30 years of age. Additionally, 3-D motion capture method was used to analyze the kinematics of the volleyball spikes and SBV. A total of 21 reflective markers were placed on specific anatomical landmarks on the surface of the skin for each player. The results of the current study revealed significant relationships (r =.56; r =.66; r =.47) between SBV and PPTSA, PUTRV, and PPRV for the DAC spikes, respectively. Although there was a modest correlation (r =.31) between SBV and PPTSA for DL spikes, it was not statistically significant and the correlation coefficients for the other DL rotational variables and SBV were very low. For the reliability study, the Cronbach's alpha coefficients across the 10 PPTSA, PUTRV, and PPRV trials were a =.98; a =.91; a =.94, respectively, indicating excellent internal consistency reliability for the CT as a measure of PPTSA, PUTRV, and PPRV. Conversely, none of the statistical analyses support the poor validity evidence of the CT as a measure of PPTSA, PUTRV, and PPRV during volleyball spiking actions. Therefore, cause and effect conclusions are not possible given the design of the current study; however, the high/moderate correlations between PPTSA and SBV for female collegiate players warrant follow-up research to examine whether or not training female outside hitters to limit the amount of pelvic rotation, thereby increasing the amount of separation (PPTSA) between the two segments at the top of the back swing, will increase SBV during either DL or DAC spikes. Even though the CT measure of-axial rotation during spiking actions indicated poor validity, the internal consistency of the measures was high. |
