Diurnal variation in drop jump performance and associated electromyographic parameters

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 degrees degrees and 17-18 degrees degrees 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.