Association Between Ground Reaction Forces And Bone Mineral Density In Male And Female Distance Runners

Bone is connective tissue that adapts to mechanical stress from weight-bearing activities like running. Running contributes to microdamage and stimulates bone development. Low bone mineral density (BMD) may occur if the rate of remodeling is outpaced by repetitive microdamages. Bone stress injuries are common among runners, especially females, which may be linked to low BMD. Current research is limited and conflicting as to whether an association exists between the ground reaction force (GRF) during running and BMD. PURPOSE: To investigate the relationship between GRF and leg BMD in male and female runners. METHODS: 28 (18 male; mean age of 26 years +/- 4.2 years; mean weekly running distance of 48.09 km +/- 28.03 km) runners underwent a dual x-ray absorptiometry (DXA) scan to calculate BMD in the spine, pelvis, and dominant leg, femur, and shank. The participants ran for 10 minutes at both a self-selected (SS) and a standardized pace (SP) of 3.33 m/s in a random order on a force instrumented treadmill to measure peak vertical GRF, peak loading rate, and vertical impulse. DXA images were manually segmented to isolate the femur and the shank individually. GRFs were normalized to body weight. Pearson correlation examined the association between GRF and BMD characteristics separately by sex, and independent samples t-tests compared outcomes between males and females (α = 0.05). RESULTS: A higher vertical impulse was associated with higher tibial BMD in males at both SS (r = 0.467, p = 0.05) and SP (r = 0.466, p = 0.5). There were no significant associations between GRFs and BMD at other sites in males (r = -0.185 - 0.425, all p > 0.05) or at any sites in females (r = -0.512 - 0.209, all p > 0.05). No body weight-normalized GRFs were different between males and females in any metric (p = 0.149 - 0.691). All BMD metrics were lower in females (mean of all sites = 1.163 g/cm2 +/- 0.15 g/cm2) compared with males (mean of all sites = 1.33 g/cm2 +/- 0.16 g/cm2) (p = <0.001 - 0.002). CONCLUSIONS: These findings indicate that the relationship between GRFs and BMD may depend on sex. Higher vertical impulse during running may be important for tibial BMD in male runners. However, female runners may benefit from alternative or supplemental training to improve leg BMD, despite having similar normalized vertical impulses compared to males during running. Supported by: Natural Science and Engineering Research Council of Canada (RGPIN-2022-04804, PI: DN Pamukoff), the Canadian Foundation for Innovation John R. Evans Leader Fund (Project ID: 42110), the Ontario Graduate Scholarship 2023-2024 (Smith), and the NSERC-Canada Graduate Scholarship (Smith)