Effects of plyometric training with and without external load on neural adaptations and lower-limb power in male collegiate sprinters

Purpose This study aimed to explore whether plyometric training with 10% body-mass external load can enhance the intensity of eccentric contractions, induce neuromuscular adaptations, and improve lower-limb power among male collegiate sprinters. Methods Twenty-three male collegiate sprinters were randomly assigned to a weighted plyometric training group (PG-Load, n=8), a bodyweight plyometric training group (PG-BW, n=8), and a control group (CG, n=7) over an 8-week intervention. Both training groups completed 8 weeks of plyometric training (two sessions/week) in addition to regular sprint training, while CG maintained regular training only. The Hoffmann (H-) reflex and M-wave tests, isokinetic strength, tendon elastography, rate of force development (RFD) and 30-m sprint performance were assessed at baseline and post-intervention. Results Significant group-by-time interactions were found for Mmax, Hmax/Mmax, H-reflex threshold, M-wave threshold, hamstring concentric/eccentric torque and RFD (all P<0.05). Post-hoc tests showed larger gains in these outcomes within PG-Load relative to PG-BW and/or CG. Quadriceps thickness, patellar tendon stiffness, jump performance, vertical stiffness and 30-m sprint performance improved significantly over time across all groups (all P<0.05). Conclusion Eight weeks of plyometric training improved neuromuscular function and lower-limb power in male collegiate sprinters. Adding external load to plyometric training elicited greater adaptations in motor unit recruitment, hamstring strength, and rapid force production, which may be partly mediated by spinal-level neuromodulatory adjustments. Weighted plyometrics may benefit sprint acceleration, though larger samples are required to verify performance transfer.