ABSTRACT
Tibial stress fractures are a problematic injury among runners. Increased loading of the tibia has been observed following prolonged weight-bearing activity and is suggested to be the result of reduced activity of the plantar flexor muscles. The musculature that spans the tibia contributes to bending of the bone and influences the magnitude of stress on the tibia during running. Participant-specific models of the tibia can be used as a non-invasive estimate of tibial stress. This study aimed to quantify tibial stress during running using participant-specific bone geometry and to compare tibial stress before and after a protocol of repeated muscular contractions of the plantar flexor muscle group. Fourteen participants who run recreationally were included in the final analysis of the study. Synchronized force and kinematic data were collected during overground running before and after an exhaustive, weighted calf-raise protocol. Bending moments and stress at the distal third of the tibia were estimated using beam theory combined with inverse dynamics and musculoskeletal modeling. Bone geometry was obtained from magnetic resonance images. There was no difference in stress at the anterior, posterior, medial, or lateral peripheries of the tibia after the calf-raise protocol compared with before. These findings suggest that an exhaustive, repeated calf-raise protocol did not alter tibial stress during running.
