Hoogkamer et al. 2016, Altered running economy directly translates to altered distance-running performance

18 sub-20-minute 5 km runners ran with 100 g and 300 g of lead added per shoe. Each 100 g per shoe raised metabolic cost by 1.11% (95% CI 0.88-1.35%) and slowed 3000 m time-trial pace by 0.78% (95% CI 0.52-1.04%). The classic ~1%-per-100-g rule, with a direct economy-to-performance link. Consistent with Franz et al. 2012 (~1% per 100 g per foot) and the older Frederick 1984 rule of thumb; note one trained-runner study (Rodrigo-Carranza 2020) reports a larger penalty near race intensity. Strong at submaximal speeds.