Biomechanics associated with bone stress injury in athletes differ by proximal and distal anatomical locations: a cross-sectional analysis.

Background: Bone stress injury (BSI) is a common overuse injury in female athletes that can occur in a variety of bones, including both proximal (pelvis, sacrum, femoral neck) or distal (tibia, fibula, metatarsals) locations. Prior work has demonstrated differences in running biomechanics in those with BSI; however, this was not separated by anatomy. We hypothesised that both female athletes with distal BSI and female athletes with proximal BSI would have lower cadence, higher centre of mass (COM) and lower duty factor than those without prior BSI. Methods: Cross-sectional study of 45 female athletes (15 with prior distal BSI, 15 with prior proximal BSI and 15 with no BSI history). Each ran on an instrumented treadmill at self-selected and 5-kilometre race speeds, with data collected in a fresh and exerted state. A series of analysis of variance tests (ANOVAs, group by condition) were used to analyse the results. Results: Participants with previous proximal BSI ran with greater vertical COM excursion compared with those with no previous BSI at race speed (10.2±1.7 cm vs 8.5±0.8 cm (p<0.001)). The proximal BSI population had a lower cadence than the no prior BSI population at race speed (170±13 steps per minute vs 180±10 steps per minute (p=0.012)). Duty factor was lower in the proximal BSI group compared with the distal BSI group at the race speed (32±3% vs 34±3% (p=0.013)). Conclusion: COM and cadence should be further investigated for association with proximal BSI.