Mechanical Variables Derived From Submaximal Back Squat Performance Are Positively Associated With Running Performance in Highly Trained Endurance Athletes

Abstract Jaén-Carrillo, D, Cartón-Llorente, A, García-Ramos, A, and Santos, L. Mechanical variables derived from submaximal back squat performance are positively associated with running performance in highly trained endurance athletes. J Strength Cond Res XX(X): 000–000, 2026—The purpose of this study was to determine the relationship between lower-body maximal neuromuscular capacities and endurance running performance. Fifteen highly trained endurance runners completed 3 sessions. The first determined one-repetition maximum (1RM) in the half squat. The second assessed maximal neuromuscular capacities ( L 0 : maximal theoretical load; V 0 : maximal theoretical velocity; A line : area under the load-velocity relationship line, used as a proxy for maximal power) and strength deficit (mean propulsive velocity MPV at 40–90% 1RM). The third measured running speed, ground contact time, cadence, and leg stiffness during 9- and 3-minute time trials. Pearson correlation analyses, with the significance level set at p < 0.05, revealed a positive association between A line and leg stiffness during both the 9-minute ( r = 0.552, p = 0.033) and 3-minute ( r = 0.580, p = 0.023) time trials. In addition, leg stiffness was also significantly associated with strength deficit, showing moderate correlations with MPV at 60% 1RM ( r = 0.585, p = 0.022) and 70% 1RM ( r = 0.555, p = 0.032) in the 9-minute trial, and at 50% 1RM ( r = 0.611, p = 0.016), 60% 1RM ( r = 0.685, p = 0.005), 70% 1RM ( r = 0.653, p = 0.008), and 80% 1RM ( r = 0.552, p = 0.033) in the 3-minute trial. Given the established association between leg stiffness and running efficiency, long-distance runners may benefit from incorporating explosive strength training with moderate to high loads (50–80% 1RM) to enhance power output and maintain propulsive force during endurance running.