ABSTRACT The exact underlying mechanisms of muscle power and strength diurnal variation are not elucidated yet. The purpose of this study was to examine the time-of-day effects on electromyographic (EMG) parameters changes during a single leg drop jump (SLDJ) in male and female athletes. Forty athletes (20 males and 20 females) performed an SLDJ at 07–08°° and 17–18°° on the same day. Surface EMG activities were recorded in the Vastus lateralis, rectus femoris, Tibialis anterior and Peroneus longus muscles throughout the SLDJ test. The root-mean-square (RMS) and mean-power-frequency (MPF) were calculated. The SLDJ performance test (18.83 ± 7.13 vs 19.72 ± 7.06 cm; p = 0.017; dz = 0.13) increased significantly from morning to evening; however, EMG activities for these muscles activity (p > 0.05) has not presented a diurnal variation.