Midsole material properties affect the amplitude but not the frequency of soft-tissue vibrations in heel-toe runners

Soft-tissue vibrations generate discomfort and thus require a greater muscle contribution to preserve an efficient motion. Besides, this may lead to an earlier onset of muscle fatigue. As a matter of fact, reducing tissue vibrations is of great interest from a comfort and performance standpoint. This study aimed at assessing the effect of shoe midsole viscoelasticity on the properties of soft-tissue vibrations in heel-toe runners. Acceleration and myographic activity were recorded for gastrocnemius and vastus medialis. With the most viscous midsole, electromyographic activity tended to decrease, and the amplitude of soft-tissue vibrations was lower. The frequency of tissue vibrations was unchanged. These results highlight that a more viscous midsole substantially reduced the amplitude of tissue vibrations, but not their frequency.