Association between bone mineral density and ground reaction force in male and female runners.

BACKGROUND

Bone responds to loading by accruing areal bone mineral density (BMD). Distance runners experience a ground reaction force (GRF) during exercise which contributes to bone loading. Sex differences in BMD reflect that males and females respond differently to running-imposed GRF.

RESEARCH QUESTION: What is the relationship between GRF and BMD in male and female runners?

METHODS

Forty participants (20 male; age=25.1 ± 4.5 years; height=1.7 ± 0.1 m; mass=67.2 ± 11.5 kg) who routinely participated in distance running (44.0 ± 26.1 km/week over 4.5 ± 1.5 weekly sessions for the past 6.9 ± 5.2 years) underwent dual x-ray absorptiometry to calculate BMD and ran on a force-instrumented treadmill to measure vertical GRF characteristics at a self-selected (SS) and at a standardized pace (SP; 3.33 m/s). Independent samples t-tests compared outcomes between males and females. Pearson correlation examined associations between GRF and BMD separately based on sex.

RESULTS

Absolute GRF and BMD outcomes were consistently lower in females compared with males (all p < 0.05). At SS, greater BMD in some sites was associated with greater vertical GRF (r = 0.582-0.793, p < 0.001-0.007), vertical loading rate (r = 0.459-0.626, p = 0.003-0.042), and vertical impulse (r = 0.518-0.759, p < 0.001-0.019) in males. Greater BMD in some sites was also associated with greater vertical GRF (r = 0.550-0.736, p < 0.001-0.012), vertical loading rate (r = 0.495-0.718, p < 0.001-0.026), and vertical impulse (r = 0.478-0.755, p < 0.001-0.033) in males at SP. There were no associations between BMD and GRF in females at either pace (r = -0.095-0.360, p = 0.130-0.983).

SIGNIFICANCE: The associations between GRF and BMD in runners differ between males and females. Supplemental training methods may be necessary for female runners to influence BMD.