PURPOSE: This study investigated the effect of an 8-week core-training program on tennis serve velocity. A second purpose was to determine the relationship between several biometric measures and serve velocity. METHODS: Seventeen men and 18 women of intermediate level (3.4 +/- 3.1 yrs tennis experience with a minimum of 1 year of tournament experience) varying from recreationally active to collegiate club players age (25.2 +/- 7.0 yrs), height (69.92 +/- 4.68 in) and weight (178.9 +/- 12.5 lbs) volunteered to participate in this study. After a 5-minute warm up and dynamic stretches, the subjects completed 25 serves of maximum velocity, which were recorded via Stalker Sport 2 radar gun (Applied Concepts Inc., Plano, TX). Serves were required to be within the service court. The 5 serves with the highest velocities were retained for analysis. After the serve test and within the same session, grip strength (Hydraulic Hand Dynamometer, Fabrication Enterprises, Inc., White Plains, NY), squat strength (5RM), bench press strength (5 RM), vertical jump height, core plank time, back extension time, arm length (acromioclavicular joint to longest finger), internal and external shoulder range of motion (Biodex 4 Isokinetic Dynamometer, Biodex Medical Systems Inc., Shirley, NY) were completed. The subjects were randomly assigned to a control and treatment group. After the pretest, the control group returned to their daily routine while participating 2-3 days/wk in tennis practice and competitive play but did not participate in a physical conditioning program. The experimental group engaged in an 8-week core training program, 2 days/wk while also participating in tennis practice and play. The first 4 weeks of core training focused on stability and endurance, while the last 4 weeks included an increased emphasis on core strength and power exercises by increasing the intensity and decreasing the volume of work. Planks, sit-ups, isolated hip flexion and extension exercises, back bridges, and medicine ball throws were included in the training program. After training, all subjects completed a posttest that included the serve velocity, core plank time and back extension time. Multiple regression with hierarchical regression was used to analyze the data. A t-test was used to examine the change score of the 2 groups for the plank and back extension time and serve velocity. RESULTS: The mean core plank improvement was significantly higher (p < 0.01) for the experimental group (51.85 s) compared to the control (22.78 s). Although improved back extension time was higher for the experimental group (32.56 s) compared to the control (13.95 s), the difference was not significant. While core times significantly improved, serve velocity in intermediate tennis players did not (p > .05). Core endurance measures were not significantly correlated with the posttest serve velocity (-0.09 <= r <= 0.36). Significant correlations were found with the following strength and power measures: bench press strength (r = .76), squat strength (r = .59), grip strength (r = .66), and vertical jump height (r = .64). Gender (r = .82), height (r = .56), and arm length (r = .39) were also significantly correlated with serve velocity. The results from the regression analysis showed that group membership was not a significant predictor of serve velocity. In addition, regression analysis determined that gender and external rotation range of motion were the significant predictors of serve velocity. CONCLUSION: The hypothesis that 8 weeks of core training would improve serve velocity in intermediate tennis players was not supported; however, several biometric measures were related to serve velocity. PRACTICAL APPLICATION: Participation in core training alone may not be an effective method for improving serve velocity, but may be effective with the addition of upper- and lower-body strength and conditioning.
(C) 2011 National Strength and Conditioning Association