Estimating tibial stress throughout the duration of a treadmill run

Abstract

Introduction: Stress fractures of the tibia are a problematic injury amongst runners of all levels. Quantifying tibial stress using a modelling approach provides an alternative to invasive assessments that may be used to detect changes in tibial stress during running. This study aimed to assess the repeatability of a tibial stress model and to use this model to quantify changes in tibial stress that occur throughout the course of a 40-minute prolonged treadmill run. Methods: Synchronised force and kinematic data were collected during prolonged treadmill running from fourteen recreational male rearfoot runners on two separate occasions. During each session, participants ran at their preferred speed for two consecutive 20-minute runs, separated by a 2-minute pause. The tibia was modelled as a hollow ellipse and bending moments and stresses at the distal 1/3 of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modelling. Results: Intraclass correlation coefficients indicated good-to-excellent repeatability for peak stress values between sessions. Peak anterior and posterior stresses increased following 20 minutes of prolonged treadmill running and were 15% and 12% greater respectively after 40 minutes of running compared with the start of the run. Conclusion: The hollow elliptical tibial model presented is a repeatable tool that can be utilised to assess within-participant changes in peak tibial stress during running. The increased stresses observed during a prolonged treadmill run may have implications for the development of tibial stress fracture.