Upper-Body Isometric Strength Qualities Are Associated With Faster High-Intensity Running Performances in Professional Soccer Players: A Cross-Sectional Study.

Curovic, I, Toskic, L, Markovic, M, Alexander, J, Suzovic, D, Grecic, D, and Harper, DJ. Upper-body isometric strength qualities are associated with faster high-intensity running performances in professional soccer players: A cross-sectional study. J Strength Cond Res XX(X): 000-000, 2026-Despite being highlighted as potentially important, the relationship between greater upper-body (UB) strength and lower-body-dominant high-intensity actions (HIA) in professional soccer players remains unknown. The aim of this study was to examine the associations between relative UB isometric strength qualities and HIA [i.e., sprinting, repeated sprint ability (RSA), change of direction (COD), vertical jumping] while controlling for leg power influence in 63 male professional players. Statistical significance was set at p ≤ 0.05. Results identified that handgrip strength (HGS), particularly rate of force development (RFD), demonstrated significant large correlations with faster 30-m sprints (r ≈ -0.52, p < 0.001) and RSA (r ≈ -0.55, p < 0.001). Upper-body maximal strength capacity (push-pull composite score) exhibited significant moderate correlations with faster RSA (r = -0.36, p = 0.004) and COD 505 test (r = -0.30, p = 0.019). Hierarchical regression analysis showed that, after controlling for leg power, UB strength accounted for an additional 12.1% of the variance in RSA performance (ΔR2 = 0.121, p = 0.004), while HGS added a further 12.4% (ΔR2 = 0.124, p = 0.002), with the full model explaining 29.3% of total variance. In conclusion, greater relative UB strength appears to be linked to superior high-intensity running performances in professional soccer players, especially during RSA tasks. Future research should investigate the effects of UB strength training through longitudinal interventions and further explore the role of UB-derived RFD metrics for HIA while accounting for horizontal lower-body force-generating capacities.