Relationships Between Loaded Countermovement Jumps and 1-RM Back Squat: A Discrete Metrics and Waveform Analysis

Background/Objectives: This study evaluated the differences in force–time characteristics of different incrementally loaded countermovement jumps (CMJs) and assessed their relationship to one-repetition maximum (1-RM) back squat performance. Methods: Nineteen resistance-trained males participated in this cross-sectional study, performing CMJs under six conditions (0%, 20%, 40%, 60%, 80%, and 100% body mass) followed by a 1-RM back squat. Multiple regression models were used to evaluate the relationship between discrete CMJ metrics (net concentric impulse, net concentric mean force, eccentric duration) with 1-RM values. Additionally, one-dimensional statistical parametric mapping (SPM) was used to evaluate the intact force–time curve between jump conditions. Results: The multiple regression models explained 53–66% of the variance in 1-RM squat performance, which was greatest under the 80% body mass condition. One-dimensional SPM analysis revealed significant differences in force–time curves across all loading conditions. Conclusions: These findings demonstrate that metrics from a loaded CMJ explained up to 66% of variance in the 1-RM back squat, suggesting the two tests are independent measures of strength. Further, each loaded jump condition elicited unique force-time curves, suggesting that each load requires a different neuromuscular technique.