Bone Functionality and Division II Male and Female Collegiate Athletes from Multiple Sports

Abstract

Participation in athletics is a risk factor for stress fracture however athletes are also viewed as icons of health, specifically bone health. Bone adaptation may vary depending on the type of loading; high or low impact sport. Are the tibiae of athletes involved in high impact sports (volleyball and soccer) functionally adapted compared to runners and swimmers? PURPOSE: To determine if Division II collegiate athletes had functionally adapted tibia (sufficient strength relative to body size) and whether functional adaptation can be determined from both the 25% and 50% tibial site. METHODS: No single variable indicates bone strength (Jepsen, 2013) and therefore cortical area (Ct.Ar), cortical bone mineral density (cBMD), moment of inertia (J) and bone strength (Strength-strain Index) were measured in 73 athletes (46 females and 27 males (age: 20.2 ± 1.7 yrs, body fat % 16.9 ± 7.5)) and 19 college student controls (8 females and 11 males (age: 23.3 ± 2.3 yrs, body fat % 21.1 ± 7.7)) using peripheral quantitative computed tomography (pQCT) at 25% and 50% of tibial length. Bone functionality was assessed by plotting bone strength vs loading (body weight x tibial length) and robustness (total area/length) vs loading. Based on the residuals from the regression, an athlete’s individual functionality was determined and two groups were formed (functionally adapted (FA) and under adapted (UA)). Student’s t-test detected differences. RESULTS: Height, weight, % body fat and tibial length were similar between the FA and UA groups. However, the FA female group had stronger (27%), more robust bones (23%), with larger moments of inertia (J) (33%) than the female UA group. Male FA group had similar cortical area and cBMD (P<0.05) as the male UA group but they had more robust (23%) stronger (26%) bones with larger J (32%). Both the 25% and 50% sites resulted in similar FA and UA groups and differences. Interestingly the FA and UA groups were comprised of athletes from all teams yet a majority of swimmers were found in the UA female group. CONCLUSIONS: Bone functional adaptation cannot be determined by anthropometric variables. FA groups had robust tibiae at the 25% and 50% site and larger J, allowing them to withstand the bending and torsional loads in sports. Determining bone functionality using the 25% or 50% site of the tibia yielded similar results.