Side-Side Radial Strength Differences In The Cortex In Female Volleyball Players Compared To Controls

Abstract

INTRODUCTION: Repetitive mechanical loading optimizes bone strength as reported in studies investigating side to side differences in within-subject models using athletes from sports with high repetitive loads and that require use of a dominant lower limb (Weatherholt and Warden, 2016). Similarly, racquet sport players yielded greater strength differences compared to controls in their racquet limb (Kontulainen et al., 2003). Such differences are not yet fully understood in female volleyball players; therefore, due to the highly repetitive striking of a dominant upper limb, the use of female volleyball players is an appropriate population to determine such strength differences. PURPOSE: To determine the percent differences in cortical strength traits between the dominant-non dominant radii in female volleyball players compared to a control group. METHODS: Division II female volleyball players (VB) (N = 16) and age-match controls (CON) (N = 15) underwent peripheral quantitative computed tomography (pQCT) scans to measure bone strength in both radii at the 66% site. Side to Side differences in cortical density (ΔCoD, mg/cm3), cortical area (ΔCoA mm2), strength strain index (ΔSSIp mm3), and moment of inertia (ΔMoI mm4) were assessed using a 2x4 mixed ANOVA. RESULTS: VB (19 yrs + 1.2); CON (22.5 yrs + 3.3). No significant differences between dominant-non dominant radii across all variables were found. Radii cortical strength variables resulted in the following ΔCoD: VB -0.96 % (CI -1.93-0.01); CON -0.45 % (CI -0.03-0.87), ΔCoA: VB 2.12% (CI -0.61-4.85); CON 1.49% (CI -0.21-3.19), ΔSSIp: VB 0.31% (CI -5.8-6.42); CON -2.66 % (CI -7.29-1.97), ΔMoI: VB 4.77 % (CI -1.39-10.93); CON 2.98% (CI -0.46-6.42). CONCLUSION: No significant differences between the dominant-non dominant radii were found in Division II female volleyball players compared to age-matched controls. However, the structural variables CoA and MoI show greater percent differences compared to control than CoD. These data suggest that volleyball may not be an appropriate model for within-subject analysis for bone adaptation due to the type of mechanical loading that is common in the sport. Factors such as start-to-play age, position, and career duration may affect these side to side differences; further investigations are needed on a larger sample size.