To run faster, distance runners need shoes that reduce their metabolic energy expenditure. Here, we studied how shoe heel-toe drop affects metabolic energy expenditure during running. To do so, we studied 20 runners as they ran at 3.5 m/s in custom footwear that varied in heel-toe drop: 0, 10, 20, and 30 mm. Shoe model and mass were fixed. Overall, increasing shoe heel-toe drop increased net metabolic power during running (η²ₚ = 0.12, p=0.016); where changing from a 20 to 0 mm heel-toe drop reduced net metabolic power by 1.6%. Higher heel-toe drop decreased average vertical ground reaction force (η²ₚ = 0.10, p=0.011) and increased average ankle effective mechanical advantage (η²ₚ = 0.28, p<0.001). Higher heel-toe drop shoes increased average ankle plantarflexion angle (η²ₚ = 0.75, p<0.001), leading to shorter medial gastrocnemius fascicle operating lengths at touch-down, toe-off, and on average during ground contact (η²ₚ ≤ 0.14 p≤0.026). Additionally, higher heel-toe drop increased peak and average knee moments during running (η²ₚ ≤ 0.40, p<0.001). Therefore, longer triceps surae muscle fascicle operating lengths and reduced knee extensor moments contribute to more economical running in shoes with a lower heel-toe drop. Based on the metabolic and biomechanical findings, recreational and high-caliber distance runners who want to run faster should opt for shoes with a zero heel-toe drop.
Renninger et al. (Sun,) studied this question.