Athletic Performance after Complex Training Compared to Traditional Strength Training.

Effects of ≥4‑week Complex Training (CT) in trained/developmental athletes (≥3×/week, local competition) are unclear. This review addressed this gap. Five databases were searched for RCTs (updated June 2025) comparing CT vs. traditional strength training on jump, agility, and sprint. Three‑level meta‑analyses with moderation and GRADE certainty assessment were used. Seventy‑five studies were included. CT produced moderate‑to‑large improvements in CMJ (62 studies; ES = 0.58, p < .01, I² = 33.99%), SJ (23; ES = 0.77, p < .01, I² = 68.59%), agility (29; ES = -1.05, p < .01, I² = 63.97%; negative = faster), and sprint (50; ES = -0.65, p < .05, I² = 56.04%). Larger effects for technical/composite and younger athletes. Dose-response meta‑regression revealed non‑linear associations. Peak CMJ at 1 rep minimum (SMD = 1.69, 95%CI [0.56, 2.81]) and 14 reps maximum (SMD = 1.36, [0.34, 2.38]). Largest agility and sprint improvements at 6 sets (agility: SMD = -1.60, [-2.37, -0.83]; sprint: SMD = -1.28, [-2.01, -0.57]) and 12 reps (sprint min.rep: SMD = -1.33, [-2.26, -0.40]), indicating attenuation at insufficient/excessive loads. Certainty moderate. CT effectively improves athletic performance, moderated by athlete characteristics and optimized by outcome‑specific dosing.