The objectives of this study were (a) to determine the concurrent validity of the flight time (FT) and double integration of vertical reaction force (DIF) methods in the estimation of vertical jump height with the video method (VID) as reference; (b) to verify the degree of agreement among the 3 methods; (c) to propose regression equations to predict the jump height using the FT and DIF. Twenty healthy male and female nonathlete college students participated in this study. The experiment involved positioning a contact mat (CTM) on the force platform (FP), with a video camera 3 m from the FP and perpendicular to the sagittal plane of the subject being assessed. Each participant performed 15 countermovement jumps with 60-second intervals between the trials. Significant differences were found between the jump height obtained by VID and the results with FT (p ≤ 0.01) and DIF (p ≤ 0.01), showing that the methods are not valid. Additionally, the DIF showed a greater degree of agreement with the reference method than the FT did, and both presented a systematic error. From the linear regression test was determined the prediction equations with a high degree of linearity between the methods VID vs. DIF (R = 0.988) and VID vs. FT (R = 0.979). Therefore, the prediction equations suggested may allow coaches to measure the vertical jump performance of athletes by the FT and DIF, using a CTM or an FP, which represents more practical and viable approaches in the sports field; comparisons can then be made with the results of other athletes evaluated by VID.

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This study aimed to investigate the acute effects of simulated judo matches on fatigue and muscle damage markers. Twenty male judo athletes participated in this study. The athletes performed three 5-minute judo matches separated by 15 minutes of passive rest between each match. The following measurements were performed before and after each match: shoulder external/internal rotation isokinetic torque and countermovement jump (CMJ). Blood samples were taken before the first match and after the third match for serum creatine kinase (CK) and lactate dehydrogenase (LDH) analysis. T-tests for dependent samples and analysis of variance for repeated measures were used to compare the variables over the time; the level of significance was set at 0.05. An overall effect of the successive matches on shoulder internal (PTIN) and external (PTEX) rotation peak torque and CMJ performance was observed. PTIN and PTEX showed significant decreases in postmatch 2 and postmatch 3 when compared with the baseline (p < 0.01). Also, CMJ height declined in postmatch 2 and postmatch 3 (p < 0.01) when compared with the baseline. Serum CK and LDH activity increased significantly after the third match (p < 0.01). It was concluded that 3 successive judo matches induced a decline of peak torque and muscle power in the upper and lower limbs, respectively, and also provoked an increase of muscle damage markers. These findings may provide important knowledge for coaches and physical trainers to improve judo-specific strength training in both the upper and lower limbs.