Effects of concurrent training on maximal and explosive strength in trained individuals: Insights from the load-velocity relationship

This study explored the effects of concurrent-training (CT), resistance-only (R) and endurance-only (E) training on back squat one-repetition maximum (1RM), load-velocity profile (LVP) parameters and countermovement jump (CMJ). Thirty trained males were randomised into three groups (E, R, CT) and trained thrice-weekly for 11-weeks. R and CT groups completed a two-phase resistance training programme: maximal-strength (weeks 1-5) and explosive-strength (weeks 6-11). E and CT groups performed 30-minutes of running within the moderate-to-heavy-intensity domains. CT involved resistance followed by endurance training. LVP parameters (L₀, V₀, Slope and A_line), 1RM and CMJ height were assessed at baseline, mid-training and post-training. Back squat 1RM increased similarly in R and CT groups during the first phase but only in R during the second phase. CMJ height increased throughout both phases for R but only during the second for CT. R increased V₀ and decreased Slope in both phases, while CT exhibited similar changes only during the second phase. A_line increased in R and CT during the first phase but improved only in R during the second. No significant changes occurred in the E group. CT impaired maximal and explosive strength adaptations compared to R, highlighting the need for tailored programmes to reduce interference effects.