Optimal design of sport footwear with considering energy dissipation of lower limb soft-tissue during running

Summary Aims Postponing muscular fatigue and preventing injuries of the lower extremity during running are common desires for professional runners. These favorites may significantly be provided via reducing the energy dissipation (ED) at the lower limb soft-tissues (LLST). It is obvious that footwear plays a main role in this matter. Use of a pair of sport shoes made by materials having optimal viscoelastic parameters can certainly help to perform a professional running. Hence, in this paper we intend to find an optimal domain for the viscoelastic parameters of sport shoes, called safe area, at which the ED at the LLST is minimum. Methods Evaluation of the ED is done based on a mass-spring-damper (MSD) model, which provides a simulated signal of the vibrating movements of the human calf muscle during running. This model is primarily validated through experimental signals recorded from vibrations of the calf muscle of eight professional runners. Frequency characterization and comparison between the simulated and recorded signals asserts the accuracy of the model. Fast Fourier Transform (FFT) as well Continuous Wavelet Transform (CWT) techniques are utilized to this end. The ED estimation is obtained by two different methods; one is statistical definition of the signal average power, the other is calculation of mechanical dissipative work. Results Results show that the safe area of shoe-specific parameters obtained based on the ED criterion is a subdomain of the one obtained based on the physiological hypothesis relied on central nervous system (CNS) functionality, namely, constant ground reaction force (GRF) peaks and minimum amplitude of muscle vibrations.