The changes in stroke production in the modern game of tennis have increased the demands on trunk rotation in elite tennis players. Unlike the shoulder where unilateral strength adaptations have been identified, no study to date has objectively quantified side to side rotational trunk strength in elite tennis players. Method: One hundred nine elite tennis players were tested using a Cybex isokinetic torso rotation unit at 60 and 120 degrees per second to measure left and right rotation while stabilized in a seated position. Subjects performed five maximal repetitions using a total arc of 90 degrees rotation (45 degrees right, 45 degrees left) for data collection with 30 seconds rest applied between testing speeds. A repeated measures ANOVA was used with post-hoc dependent t-tests where main effect differences were identified to determine side to side rotational differences. Results: No significant difference between left and right trunk rotation strength was measured in the elite male players. Peak torque to body weight ratios averaged 63.7% and 57.5% for forehand rotation (left rotation in right handed player) and 64.4% and 59.2% for backhand rotation at 60 and 120 degrees per second respectively. In females, slightly greater (p<.001) backhand rotation strength (right rotation in a right handed player) was measured at both testing speeds with peak torque to body weight ratios ranging between 47.7% and 45.1% for left rotation and 50.8% and 48.3% for right rotation at 60 and 120 degrees per second respectively. Left rotation/right rotation ratios ranged between 95-98% for males and 94-96% for females. Conclusion: Elite level male tennis players have symmetric trunk rotation strength. Elite female tennis players have slightly greater backhand rotation strength (by 4-8%) than forehand rotation. Conditioning programs for elite tennis players should include exercises to facilitate and develop bilateral trunk rotation. Symmetrical trunk rotation strength is expected during the evaluation of the elite level tennis player. Descriptive generated in this study is meant to assist clinicians in the evaluation of trunk strength in elite tennis player for both performance enhancement as well as injury prevention and rehabilitation.
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