Heavy strength work improves running economy. This is the single-leg version.
Balsalobre-Fernández et al., 2016 · Meta-analysis: Strength and plyometric training 2–3 times a week for 8–12 weeks produced a large improvement in running economy. (Highly trained middle- and long-distance runners only.)
Blagrove et al., 2018 · Review: Strength training generally improved running economy by 2–8% and tended to improve 1.5–10 km time trials, without hurting body composition. (24 studies; not every study found a benefit.)