Abstract
CONTEXT: Overhead-throwing athletes consistently display substantial bilateral differences in humeral retroversion (HRV). However, evidence is limited regarding HRV asymmetries in tennis players despite similarities between the overhead throw and tennis serve. OBJECTIVE: To determine whether (1) junior and collegiate tennis players demonstrated bilateral differences in HRV and (2) the magnitude of the HRV side-to-side difference (HRVΔ) was similar across age groups. DESIGN: Cross-sectional study. SETTING: Field-based setting. PATIENTS OR OTHER PARTICIPANTS: Thirty-nine healthy tennis players were stratified into 3 age groups: younger juniors (n = 11, age = 14.5 ± 0.5 years), older juniors (n = 12, age = 17.1 ± 0.9 years), and collegiate (n = 16, age = 19.6 ± 1.2 years). MAIN OUTCOME MEASURES: Three-trial HRV means were calculated for the dominant and nondominant limbs, and HRVΔ was obtained by subtracting the mean of the nondominant side from that of the dominant side. A paired-samples t test was used to determine bilateral differences in HRV, and a 1-way analysis of variance was used to compare HRVΔ among groups. RESULTS: For all 3 groups, HRV angle was greater in the dominant versus nondominant upper limb (younger juniors = 62.9° ± 9.1° versus 56.3° ± 6.8°, P = .039; older juniors = 75.5° ± 11.2° versus 68.6° ± 14.2°, P = .043; collegiate = 71.7° ± 8.5° versus 61.2° ± 6.9°, P = .001). However, no differences were detected in HRVΔ across age groups (P = .511). CONCLUSIONS: Consistent with the findings of previous studies of overhead-throwing athletes, we demonstrated greater measures of HRV in the dominant limb of tennis players. Furthermore, HRV asymmetries appeared to have developed before the teenage years, as no changes were observed in HRVΔ among age groups.