Plyometrics
Evidence: moderate
Jump and bounding training improves running economy by sharpening elastic energy return, a useful complement to heavy strength work, which has a slightly larger effect.
Plyometrics are explosive jump, hop and bounding exercises that train the stretch-shortening cycle: the rapid stretch-then-shorten of muscle and tendon that stores and returns elastic energy with each stride. For runners the interest is running economy. Adding plyometric training improves economy, with effect sizes that are real but modest, and slightly smaller than those from heavy resistance training (Eihara et al. 2022; Blagrove et al. 2018).
The mechanism fits the economy evidence: better elastic recoil and greater muscle-tendon stiffness mean more of each stride is “free”, returned from stored energy rather than paid for metabolically. Plyometrics develop exactly that quality, which is why they complement rather than duplicate heavy strength work, which builds force, and the two are often programmed together (Balsalobre-Fernández et al. 2016).
Build up before you bound
Plyometrics are high-impact, and the forces are large. They belong on a base of general strength and conditioning, introduced gradually, starting with low-intensity hops and skips before high-impact bounds and depth jumps. Loaded onto unprepared legs, especially alongside high running volume, they are a route to tendon and bone injury, the slow-adapting tissues. Quality and landing mechanics matter more than volume; a small dose, well executed, is the goal.
For most runners, a short plyometric routine once or twice a week, integrated with strength training, is a sensible way to capture the economy benefit. It is a complement to running and lifting, not a substitute for either.