1. COLLEGIATE VOLLEYBALL ATHLETES
ROTATIONAL VELOCITIES, PELVIC: TORSO SEPARATION, AND SPIKED BALL VELOCITY IN FEMALE
COLLEGIATE VOLLEYBALL ATHLETES
Bader J. Alsarraf1, Justin R. Brown2, Mike Waller4, Patricia Eisenman2, Charlie A. Hicks-Little3
1Department of Physical Education and Sport, College of Basic Education in Kuwait, Adailiya, Kuwait;
2Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah;
3Sports Medicine Research Laboratory, Department of Exercise and Sport Science, University of Utah, Salt Lake City, Utah; and
4Department of Human Performance and Physical Education, Adams State College, Alamosa, Colorado
ABSTRACT
Introduction: High velocity spikes are an important skill for a successful volleyball offense. Although the influence of vertical jump height and arm speed variable on spiked ball velocity (SBV) have been investigated, little is known about the influence of variables such as pelvic rotation, torso rotation, and pelvic-torso separation on SBV. The purpose of this study was to examine the relationship between peak pelvic-torso separation angle (PPTSA), peak upper-torso rotational velocity (PUTRV) and peak pelvic rotational velocity (PPRV) and SBV. Methods: Fourteen Division I collegiate volleyball players executed 10 down the line (DL) and 10 diagonally across court (DAC) spikes. Motion-capture analysis was used to measure the rotational variables and SBV. Results: DL ball velocity was significantly greater than DAC velocity (17.54±2.35 vs ±2.36 m/s, p<0.05). Peak pelvic-torso separation angle (PPTSA), peak upper-torso rotational velocity (PUTRV) and peak pelvic rotational velocity (PPRV) were all significantly correlated with DL SBV. Regression analysis indicated that PPTSA was the most significant predictor of SBV. Conclusions: Since PPTSA was the most significant factor related to SBV, additional research to determine optimal PPTSA and strategies for achieving optimal PPTSA are warranted.
INTRODUCTION
Being able to impart a high velocity during a volleyball spike requires the spiker to coordinate a number of complex movement patterns (1,2). In rotational sport skills such as volleyball, one of the primary goals is to impart a high velocity to the ball. A high velocity spike is more difficult to defend and as one factor important to a successful offense. Kinematic analyses of baseball pitchers have demonstrated that as ball velocity increased, pitchers displayed a more open pelvis when the upper torso position was at the point of maximum shoulder external rotation. Having an open pelvis position allowed for greater pelvic rotation, resulting in a greater peak pelvic rotational velocity and because the upper torso rotates after the pelvis, the later upper torso rotation can build upon the pelvic rotational velocity, resulting in a greater upper torso rotational velocity. The timing of the pelvic and upper torso rotations is critical for transferring high velocity to the pitched ball. This timing pattern is known as the X-factor (3), or pelvic-torso separation (Figure 1.). It is thought that by increasing the amount of separation there is an increase in the stored energy in the core musculature (4). Theoretically, during the forward phase of the volleyball spike the energy stored due to the backswing is released, contributing to the velocity imparted to the ball. The imparted ball velocity is optimal if the forward phase is initiated with forward pelvic rotation first, followed by upper torso rotation, and then the sequential movements of the arm, wrist, and hand (3).
The purpose of this study was to examine the relationship between peak pelvic separation angle, peak upper torso rotational velocity (PUTRV), peak pelvic rotational velocity (PPRV), and spiked ball velocity in female spikers. Because the direction of the spike might influence the PPTSA, PUTRV, as well as PPRV, down-the-line (DL) spikes were compared with diagonally across-court (DAC) spikes. Based on the work of Coleman et al. ( ), we hypothesized that DL spikes will have significantly greater PPTSA, PUTRV, as well as PPRV, resulting in greater SBV than DAC spikes.
Figure 1. Definition of the upper torso rotation, pelvic rotation and pelvic-torso separation angles.
HYPOTHESIS
DL spikes will have significantly greater PPTSA, PUTRV, as well as PPRV, resulting in greater SBV than DAC spikes.
METHODS
Fourteen Division I female volleyball players (age 20.9±2.8 yrs, height 181.6±7.7 cm, weight 72.9±12.5 kg, BMI 22.0±3.0 kg/m2, body fat 22.0±6.3 percent, playing experience 3.2±1.4 years) volunteered for the study. Body composition was assessed using Air Displacement Plethysmography. A 10 camera 3-D Motion Analysis System (Motion Analysis Corporation, Santa Rosa, CA) was utilized to examine the kinematics of the volleyball spike. Participants were fitted with a total of 21 reflective markers (19 mm) (Figure 2). Motion capture analysis measured pelvis and upper torso velocity, degrees of separation between the pelvis and upper torso, and ball velocity. Three reflective makers were placed on an official size and weight Baden® Lexum™ Comp VX450 volleyball. The ball was held in position by a SPIKE IT® to decrease variability between sets. Using a 3-4 step approach participants performed one set of DL and one set of DAC spikes (Figure 3). Each set consisted of 10 spikes and the order of the sets was randomized. A 5 minute rest period was given between each set and a 30 seconds rest between each volleyball spike.
Table 1. Spiked ball velocity and peak pelvic torso separation for down the line and diagonal cross court spikes.
Table 2. Significant correlations for ball velocity and other variables during diagonal cross court spike.
CONCLUSIONS
These data demonstrate a significantly greater SBV for DL versus DAC spikes and that PPTSA was the most important predictor of SBV. Significant relationships were seen between PPTSA, PUTRV, PPRV, and SBV for DAC spikes only. Interestingly, the DAC spikes were slower yet had greater PPTSA. Using the Spike It in the same position for both the DL and DAC trials may have influenced the spiking technique of the spikers. Future studies should allow for optimal positioning of the Spike It for both DL and DAC spikes as well as examine the use of set balls rather than ball in fixed positions. Incorporating core rotational exercises into strength and conditioning programs of outside hitters may help improve SBV for DAC spikes. In addition, spiking drills that emphasize creating a pelvis-torso separation during the backswing may help players impart more velocity to the spiked ball.
REFERENCES
Ferris, DP, Signorile, JG, and Caruso, JF. The relationship between physical and physiological variables and volleyball spiking velocity. Journal of Strength and Conditioning Research 9(1): 32–36, 1995.
Forthomme, B, Croisier, J, Ciccarone, G, Crielaard, J, and Cloes, M. Factors correlated with volleyball spike velocity. American Journal of Sports Medicine 33(10): 1513–1519, 2005.
Myers, J, Lephart, SM, Tsai, YS, Sell, TC, Smoliga, JM, and Jolly, JT. The role of upper torso and pelvis rotation in driving performance during the golf swing. Journal of Sports Sciences 26(2): 181–188, 2008.
Stodden, DF, Fleisig, GS, McLean, SP, and Andrews, JR. Relationship of biomechanical factors to baseball pitching velocity: Within pitcher variation. Journal of Applied Biomechanics, 21, 44–56, 2005.
Variable DL
DAC
P-value
SBV (m/s)
17.54 ± 2.35
15.97 ± 2.36
.039
PPTSA (°)
-9.16 ± 5.32
± 5.36
.043
Variable r
P-value
Peak pelvic torso separation angle
.56
.019
Peak upper torso rotational velocity
.66
.005
Peak pelvic rotational velocity
.47
.044
Figure 2. Participant attire and reflective marker placement.
Figure 3. Down the line and diagonal cross court spikes for right and left handed players.
RESULTS
SBV was statistically greater for the DL spike (Table 1). Statistically significant differences were also seen for PPTSA between DL and DAC spikes (Table 1). For the DAC spikes, moderate positive correlation coefficients were observed between: SBV and PPTSA as well as SBV and PUTRV. No significant correlations were observed for the DL spikes. A multiple regression analysis revealed the most important predictor of SBV was PPTSA for DAC SBV.