Purpose:To determine what variables determine the differences in performance on 2 tests of squat jump (SJ) performed under light load in highly trained athletes using maximal velocity (V_max) or flight time (FT) as the discriminating factor of SJ performance.Methods:Thirty-two participants performed 2 maximal weighted SJs using a force platform synchronized with a linear transducer. Mean force (F_mean), mean and maximal power (P_mean, P_max), peak force (PF), maximal rate of force development (RFD_max), and time required to attain PF (TPF) and RFD_max (TRFD_max) were analyzed. SJs were divided into 2 segments: from the initiation of force application to PF₁ and from the moment after PF₁ to V_max.Results:Traditional significance statistics revealed significant differences in the same variables between best and worst SJs using both FT and V_max. However, to use an approach based on the magnitude of the effect, the best SJ showed greater P_max (83/17/0%), P_mean (85/15/0%), F_mean (71/29/0%), RFD_max1 (73/27/0%), and PF₁ (53/47/0%) and lower TPF₂ (0/61/39%) than the worst SJ when V_max was used to discriminate SJ performance. However, using FT to differentiate SJ performance, no difference was observed between best and worst.Conclusions:Although jump height assessed through FT is a valid measure, these results suggest that V_max is a more sensitive variable than FT to detect differences in loaded-SJ performance.