Comparison of Tibial Strength Between Adult Female Dancers, Gymnasts, and Runners

Abstract

The magnitude, frequency, and patterns of mechanical loading are important factors in how weight-bearing bones adapt their strength. Overall, adolescent and adult female athletes that participate in high impact physical activity have greater gains in bone strength than athletes that participate in low-repetitive impact activities (Nichols et al., 2007, Uusi-Rasi et al., 2006, and Nikander et al., 2010); however, it is not clear how medium impact activities (dance) compare to high impact activities (gymnastics) and low-repetitive activities (running) with respect to their osteogenic effects at the tibia. PURPOSE: To compare tibial strength between female adult dancers, gymnasts, and runners. METHODS: Eleven eumenorrheic dance majors and eleven eumenorrheic collegiate gymnasts (ages 18–22) were recruited. Runner (n=22) and sedentary control (n=19) data were obtained from the University of Minnesota Laboratory of Musculoskeletal Health database (Smock et al., 2009 and Bruininks, 2009). Participants’ non-dominant tibias were scanned using peripheral quantitative computed tomography at two locations - 4% (metaphyseal) and 66% (diaphyseal) sites from the distal tibia endplate. The scans provided two estimates of bone strength; bone strength index (BSI; mg.mm-4/10,000) and polar strength-strain index (SSIp, mm3). BSI is an estimate of bone compressive strength at metaphyseal sites and SSIp is an estimate of bone’s ability to resist torsion at diaphyseal sites (Smock et. al. 2009; Farr et al. 2010). BSI at the 4% site and the SSIp at the 66% site were compared between groups using linear regression models. RESULTS: Participants did not differ in age, weight, or tibial length. After controlling for height and body mass, SSIp did not differ significantly between groups. Dancers, gymnasts and runners had significantly greater BSI (33.2%, 43.7% and 20%, respectively) than controls (p=0.001, p<0.001, and p=0.03, respectively). CONCLUSIONS: Despite differences in impact type, dance, gymnastics, and running appear to be effective at increasing distal tibia compressive strength - which is known to delay or prevent bone fragility later in life. Future studies should analyze the magnitude and frequency of loadings to further identify which activities provide the greatest osteogenic benefits in adult females.