Effect of muscle fatigue on metabolic cost in running and implications for footwear design

Metabolic cost and muscle fatigue are important and interrelated criteria that influence running performance. Runners incur a greater metabolic cost when running with fatigued lower limb muscles (induced by an exhaustive bout of running) than when running with unfatigued muscles (Nicol et al., 2007). However, it remains unclear how individual muscle groups contribute to the observed metabolic penalties. Of particular interest are the knee extensors (KE), due to their large volume and important role in locomotion. Because midsole cushioning and KE behaviour can both affect impact attenuation during running, shoe design may influence the relationship between metabolic cost and KE fatigue. Unfortunately, the relationship between metabolic cost and KE fatigue is not yet well understood.