Author(s): LU, J., GIRARD, O., THAPA, R.K., Institution: BEIJING SPORT UNIVERSITY, Country: CHINA, Abstract-ID: 689

INTRODUCTION:
Combined contrast training (CCT) pairs a heavy-resistance exercise with a biomechanically similar ballistic or plyometric exercise within the same session. We quantified chronic CCT effects on jump, sprint, and strength outcomes and tested whether training exposure and within-session structure explain between-study variability.
METHODS:
PRISMA-guided systematic review and multilevel meta-analysis (PROSPERO CRD420251244479) of chronic CCT interventions (>=4 weeks). The primary synthesis compared CCT with non-CCT comparators; paired versus blocked head-to-head contrasts were extracted and summarised separately. Multilevel random-effects models with CR2 cluster-robust inference were used (Hedges’ g for CMJ; mean difference (MD) for sprint time and 1RM), and 95% prediction intervals (PI) were reported. Sprint times were sign-reversed so positive MD indicates faster performance. Dose-response meta-regressions estimated the change in effect per doubling of total training minutes or total sessions and were interpreted as study-level associations, not causal prescriptions.
RESULTS:
Fifty studies met inclusion criteria; 41 studies (total n=1290) contributed to quantitative synthesis. Compared with non-CCT controls, CCT improved CMJ (g=0.603, 95% CI 0.400 to 0.805; PI -0.288 to 1.493; k=29), improved 10-m sprint performance (MD=0.056 s, 95% CI 0.025 to 0.087; PI -0.042 to 0.154; k=15), and increased squat 1RM (MD=15.611 kg, 95% CI 10.402 to 20.819; PI -6.540 to 37.761; k=23). CMJ effects increased with greater total minutes (slope=0.512 g per doubling, 95% CI 0.081 to 0.942; p=0.024; k=27), and sprint improvements increased with more total sessions (slope=0.064 s per doubling, 95% CI 0.031 to 0.097; p=0.004; k=14). Pr(>=MCID) was 0.82 for CMJ (0.20 SMD), 0.71 for 10-m sprint (0.030 s), and 0.83 for squat 1RM (5.0 kg). Head-to-head paired versus blocked organisation (18 studies; 109 contrasts) was inconsistent and not pooled.
CONCLUSION:
CCT improved jump, sprint, and squat strength on average, but PI indicated substantial context-dependent variability. In measurement-consistent subsets, CMJ heterogeneity decreased to I2=0.0 (Optojump-only), whereas sprint heterogeneity remained high in a photocell/standing-start subset, suggesting that sprint variability is less likely to be a measurement artefact. For sprint, residual tau2 decreased by 39.4% after accounting for intensity matching and biomechanical similarity (isomorphic pairing), indicating that pairing precision may contribute beyond exposure alone. Overall, the pattern was consistent with more exposure-sensitive jump outcomes and more structure-sensitive sprint outcomes within the range of programmes studied. Evidence remains insufficient to recommend a single paired versus blocked organisation, highlighting the need for more transparent reporting of CCT dose and pairing characteristics to support clearer practical recommendations.