Calf Muscle Strategy For Tibia Bone Load According To Gait Speed

Tibial bone stress injury (BSI) is a common injury among military people and runners who participate in activities that involve persistent and repetitive force on the tibia, such as marching or long-distance running. The majority of research accounts for bone load by only monitoring Ground Reaction Force (GRF) characteristics such as loading rate and impact peak. Internal bone load, on the other hand, is related not only to external force (GRF) but also to internal muscle forces. It is also unclear how internal muscle forces affect internal bone load when changing gait speed. PURPOSE: The purpose of this study is to investigate the effect of gait speed on tibia compressive force (TCF) and the calf muscle strategy associated with TCF. METHODS: This study was conducted using a previously published dataset. Ten experienced long-distance male runners completed running trials at various speeds (2.0 m/s, 3.0 m/s, 4.0 m/s, 5.0 m/s), and kinematic, kinetic, and electromyography data of the calf muscles (SOL: Soleus, LG: Lateral Gastrocnemius, MG: Medial Gastrocnemius) were collected during each trial. Participant-specific musculoskeletal models were used to obtain joint moments and estimated muscle forces via inverse dynamics and static optimization. These variables were then used to determine peak TCF acting on the distal tibia during the stance phase and calf muscle force at peak TCF. A one-way repeated measures ANOVA was performed to compare peak TCF and calf muscle force across different gait speeds. RESULTS: The TCF and SOL force increased with faster gait speeds (Table 1). At all speeds, SOL force was significantly higher, followed by MG force, and LG force (Table 1). CONCLUSION: These results suggest that increasing gait speeds increase tibial compressive force due primarily to concomitant increases in SOL tensile force. When developing programs to reduce the risk of BSI or for rehabilitation, prioritizing a reduction in SOL force is advisable.