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This study examined the effects of systematically modifying two Advanced Footwear Technology (AFT) components, the curved carbon fibre plate and the polyether block amide (PEBA) midsole material, on the energetic cost of running (Erun) and muscle activation. Sixteen male recreational runners performed treadmill running trials in three shoe conditions: the standard Nike Vaporfly 4% (Original VP4), a prototype without the carbon fibre plate (No Plate), and a prototype with EVA foam replacing the PEBA foam (EVA). Erun was quantified using indirect calorimetry, and muscle activation of the gastrocnemius medialis and soleus muscles was assessed using surface electromyography (EMG). The results showed that Erun was significantly lower in the Original VP4 condition compared to both the No Plate and EVA conditions, by 1.87% and 2.23%, respectively. However, changes in muscle activation were not statistically significant across shoe conditions. These findings suggest that both the curved carbon fibre plate and PEBA foam in the Vaporfly 4% contribute to reduced Erun, through mechanisms other than reduced activation of the selected plantar flexor muscles.
Subramanium et al. (Sun,) studied this question.