effect eccentric phase duration on maximal strength, muscular hypertrophy and countermovement jump

Some authors suggest slower eccentric tempos enhance resistance training (RT) adaptations, and narrative reviews yield divergent conclusions. PubMed, CINAHL, SPORTDiscus, ProQuest, and Google Scholar were searched following Cochrane Handbook and PRISMA-guidelines, to compare RT outcomes following fast (FEG) and slow (SEG) eccentric phases. Random-effects multi-level meta-analyses with robust variance estimation was performed for strength, hypertrophy, and countermovement jump (CMJ), with results interpreted relative to a region of practical equivalence. Evidence quality was assessed using the Cochrane RoB 2 and GRADE criteria. Eight studies involving 148 participants (52% trained, 80% male) were included. FEG enhanced CMJ by a practically worthwhile degree with moderate certainty (Hedge's g = -0.73 [90% CI = -1.34, -0.12; 90% PI = -1.34, -0.12]), while uncertain estimates for maximal strength (g = 0.18 [90% CI = -0.27, 0.63; 90% PI = -0.96, 1.31]) and muscle hypertrophy (g = 0.03 [90% CI = -0.30, 0.36; 90% PI = -0.32, 0.38]) meant that practically worthwhile effects could neither be supported nor rejected. SEG led to practically equivalent or enhanced strength gains, compared to FEG, in trained participants (g = 0.33 [90% CI = 0.07, 0.60; 90% PI = 0.07, 0.60]) and volume-load matched trials (g = 0.25 [90% CI = 0.04, 0.45; 90% PI = 0.04, 0.45]) with moderate certainty in subgroup analyses. FEG may enhance CMJ, while SEG may cause similar or higher maximal strength increases in trained participants and volume-load matched conditions. Given the uncertainty of estimates, more research is needed. This project was prospectively registered (https://osf.io/s6uqn/).