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
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©Journal of Sports Science and Medicine (2016) 15, 148 - 157

Research article
Limitations of Spectral Electromyogramic Analysis to Determine the Onset of Neuromuscular Fatigue Threshold during Incremental Ergometer Cycling
Iban Latasa1, Alfredo Cordova2, Armando Malanda1, Javier Navallas1, Ana Lavilla-Oiz3, Javier Rodriguez-Falces1, 
Author Information
1 Department of Electrical and Electronical Engineering. Public University of Navarra, Pamplona, Spain
2 Department of Physiology and Biochemistry. University of Valladolid, Soria, Spain
3 Pediatric Neurology Unit., Complejo Hospitalario de Navarra, Pamplona, Spain

Javier Rodriguez-Falces
✉ Universidad Pública de Navarra D.I.E.E., Departament of Electrical and Electronical Engineering, Campus de Arrosadía s/n. 31006 Pamplona. Spain.
Email: javier.rodriguez.falces@gmail.com
Publish Date
Received: 03-12-2015
Accepted: 04-01-2016
Published (online): 23-02-2016
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ABSTRACT

Recently, a new method has been proposed to detect the onset of neuromuscular fatigue during an incremental cycling test by assessing the changes in spectral electromyographic (sEMG) frequencies within individual exercise periods of the test. The method consists on determining the highest power output that can be sustained without a significant decrease in spectral frequencies. This study evaluated the validity of the new approach by assessing the changes in spectral indicators both throughout the whole test and within individual exercise periods of the test. Fourteen cyclists performed incremental cycle ergometer rides to exhaustion with bipolar surface EMG signals recorded from the vastus lateralis. The mean and median frequencies (Fmean and Fmedian, respectively) of the sEMG power spectrum were calculated. The main findings were: (1) Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods. (2) Examination of the whole incremental test showed that the behaviour of Fmean and Fmedian with increasing power output was highly inconsistent and varied greatly among subjects. (3) Over the whole incremental test, half of the participants exhibited a positive relation between spectral indicators and workload, whereas the other half demonstrated the opposite behavior. Collectively, these findings indicate that spectral sEMG indexes do not provide a reliable measure of the fatigue state of the muscle during an incremental cycling test. Moreover, it is concluded that it is not possible to determine the onset of neuromuscular fatigue during an incremental cycling test by examining spectral indicators within individual exercise periods of the test.

Key words: Cycling, neuromuscular fatigue, surface electromyography, motor unit recruitment, spectral EMG analysis


           Key Points
  • The behaviour of spectral EMG indicators during the incremental test exhibited a high heterogeneity among individuals, with approximately half of the participants showing a positive relation between spectral indicators and workload and the other half showing the opposite behaviour.
  • None of the spectral EMG indicators examined (Fmean nor Fmedian) decreased significantly between the ventilatory threshold and the highest power output.
  • Examination of spectral indicators within individual exercise periods of the test showed that neither Fmean nor Fmedian decreased significantly during the last (most fatiguing) exercise periods.
 
 
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