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A Journal on Sports Medicine

Official Journal of the Italian Sports Medicine Federation
Indexed/Abstracted in: BIOSIS Previews, EMBASE, Science Citation Index Expanded (SciSearch), Scopus
Impact Factor 0,163

Frequency: Quarterly

ISSN 0025-7826

Online ISSN 1827-1863


Medicina dello Sport 2014 June;67(2):185-93


Reliability of electromyography and peak torque during maximum voluntary concentric, isometric and eccentric contractions of quadriceps muscles in healthy subjects

Carvalho A. 1, Abade E. 1, 2, Carvalho C. 1, Sampaio J. 1, 2

1 Research Center of Sports Science, Health and Human Development (CIDESD), High Institute of Maia, Maia, Portugal;
2 University of Trás-os-Montes e Alto Douro (UTAD), Vila Real, Portugal

AIM: The aim of this study was to investigate the reliability of surface electromyography of the average full wave rectified signal (AvgEMG) of each muscle. Also, the peak torque (PT) of the subjects’ best performance during maximum voluntary concentric, eccentric and isometric contractions of quadriceps was recorded. Considering that EMG interpretation of dynamic contractions might become difficult, based on the fact that movement itself may affect the signal characteristics, it was also examined the AvgEMG reliability without electrode removal, after a one hour resting period and with electrode removal with a one week interval.
METHODS: The EMG signals of Vastus lateralis (VL), Rectus femoris (RF) and Vastus medialis (VM) muscles were recorded in 16 subjects (males) using surface electrodes (Medicotest, Blue Sensor SP). These data were analyzed considering the AvgEMG of each muscle and its corresponding intra-class correlation coefficient (ICC).
RESULTS: The results of this study show that PT and AvgEMG obtained high reliability without electrode removal, one hour after the resting period (PT ICC: 0.98 to 0.99; AvgEMG ICC: 0.71 to 0.97). In addition, it was observed a high reliability in all of the variables regarding the results obtained with electrode removal, one week after the resting period (Isometric PT ICC: 0.90; Concentric PT ICC: 0.95; Eccentric PT ICC 0.95; AvgEMG ICC: 0.80 to 0.94). This study demonstrated that one hour after the resting period without electrode removal, PT and EMG variables revealed high reliability and that one week after the resting period with electrode removal they still indicate good reliability of PT and EMG variables.
CONCLUSION: The RF muscle seems to present less reliable results than VL and VM muscles. When the electrodes are removed, the reproducibility seems to decrease, probably due to the electrode replacement related factors.

language: English, Italian


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