Do plantar flexor muscle structure and function contribute to medial tibial stress syndrome in long-distance runners? A case report

Two long-distance runners developed MTSS (male age=26.3 years, female age=47.5 years) after baseline assessment of plantar flexor muscle structure and function and spatiotemporal running variables. B-mode ultrasound and lean leg girth characterized plantar flexor muscle structure. Hand-held dynamometry and a single-leg heel raise to failure protocol characterized plantar flexor muscle function. Finally, spatiotemporal running variables were determined during a treadmill protocol. The two runners who developed MTSS demonstrated less plantar flexor strength and endurance capacity than published comparative control data and marked variability in muscle structure. Reduced plantar flexor strength and endurance capacity were thought to contribute to an impaired ability to resist tibial bending moments during midstance due to earlier muscle fatigue. Earlier muscle fatigue could, in turn, contribute to increased tibial bending moments and MTSS development. Therefore, assessing plantar flexor muscle strength and endurance might help to identify athletes at risk of developing MTSS.