Journal of Sports Science and Medicine
Journal of Sports Science and Medicine
ISSN: 1303 - 2968   
Ios-APP Journal of Sports Science and Medicine
Androit-APP Journal of Sports Science and Medicine
from September 2014
©Journal of Sports Science and Medicine (2012) 11, 380 - 386

Research article
Time-of-Day Effects on EMG Parameters During the Wingate Test in Boys
Hichem Souissi1,2, , Hamdi Chtourou1,2, Anis Chaouachi1, Karim Chamari1,3, Nizar Souissi1,3, Mohamed Amri4
Author Information
1 Research Laboratory “Sports performance optimization” National Center of Medicine and Science in Sports (CNMSS), Tunis, Tunisia
2 Research Unit, High Institute of Sport and Physical Education, Sfax University, Tunisia
3 High Institute of Sport and Physical Education, Ksar-Saïd, Manouba University,, Tunisia
4 Laboratory of Functional Neurophysiology and Pathology, Faculty of Sciences Tunis, Tunisia

Hichem Souissi
✉ Laboratoire de recherche “Optimisation de la performance sportive“ , Centre National de la Médecine et des sciences du sport,Bp263, Ave Med Ali Akid, 1004 El Menzah, Tunis, Tunisa
Publish Date
Received: 24-11-2011
Accepted: 04-05-2012
Published (online): 01-09-2012
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In boys, muscle power and strength fluctuate with time-of-day with morning nadirs and afternoon maximum values. However, the exact underlying mechanisms of this daily variation are not studied yet. Thus, the purpose of this study was to examine the time-of-day effects on electromyographic (EMG) parameters changes during a Wingate test in boys. Twenty-two boys performed a 30-s Wingate test (measurement of muscle power and fatigue) at 07:00 and 17:00-h on separate days. Surface EMG activity was recorded in the Vastus lateralis, rectus femoris and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root-mean-square (RMS) and mean-power-frequency (MPF) were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Muscle power (8.22 ± 0.92 vs. 8.75 ± 0.99 W·kg-1 for peak power and 6.96 ± 0. 72 vs. 7.31 ± 0.77 W·kg-1 for mean power, p < 0.001) and fatigue (30.27 ± 7.98 vs. 34.5 ± 10. 15 %, p < 0.05) during the Wingate test increased significantly from morning to evening. Likewise, MPF (102.14 ± 18.15 vs. 92.38 ± 12.39 Hz during the first 5-s, p < 0.001) and NME (4.78 ± 1.7 vs. 3.88 ± 0.79 W·mV-1 during the first 5-s, p < 0.001) were higher in the evening than the morning; but no significant time-of-day effect was noticed for RMS. Taken together, these results suggest that peripheral mechanisms are more likely the cause of the child’s diurnal variations of muscle power and fatigue during the Wingate test.

Key words: Dkwdurnal variation, muscle power, muscle fatigue, electromyography, pre-pubertal

           Key Points
  • In boys, performances during the Wingate test fluctuate with the time-of-day.
  • MPF and NME are higher in the evening during the Wingate cycling test.
  • RMS is unaffected by the time-of-day.
  • The evening improvement in muscle power and fatigue is due to an enhancement of the muscle contractile properties.
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