Machine-based based subtalar pronator and supinator strength training increases rearfoot stability in male runners

Excessive pronation and increased pronation velocity of the foot due to excessive Subtalar Joint (STJ) motion have been discussed as major intrinsic factors for the pathophysiology of overuse running injuries. A possible strategy to reduce these risk factors is the use of the supinator muscles acting eccentrically during the support phase of running. We hypothesised that STJ-specific strength training of the supinator and pronator muscles would be more effective in reducing rearfoot motion compared to traditional plantarflexor and dorsiflexor exercises. Twenty healthy male (20-35 years) recreational runners performed machine-based Subtalar Training (ST) with the right foot and machine-based plantar-/ dorsiflexor taining around the Talocrural joint (TT) with the left over a period of ten weeks. STJ muscle strength and shank muscle volume were measured in pre- and posttest. Furthermore, rearfoot motion during overground running (3.3 m/s) was analysed. The multifactorial analyses showed significant increases in muscle strength and volume (p < 0.001). Interaction effects (time x group) revealed higher strength increases for ST (p < 0.001) and higher muscle volume increase in the deep supinator muscles (p < 0.05) for ST. The analyses of rearfoot motion showed significant changes after the treatment indicated by a higher inversion angle at touchdown (p < 0.01) and reduced eversion velocity in mid-stance (p < 0.01). Both effects were higher after ST (p < 0.01; time x group interaction). Machine-based subtalar-specific strength training represents a potential prevention strategy for male runners to enhance the function of the supinator muscles, to stabilise rearfoot motion during running and, therefore, to reduce lower limb injury risk.