Next Article in Journal
Age-Related Differences in the Physical and Physiological Demands during Small-Sided Games with Floaters
Previous Article in Journal
Does Perception of Motor Competence Mediate Associations between Motor Competence and Physical Activity in Early Years Children?
Previous Article in Special Issue
Thinking Outside the Block: External Focus of Attention Improves Reaction Times and Movement Preparation Times in Collegiate Track Sprinters
Article Menu
Issue 4 (April) cover image

Export Article

Open AccessFeature PaperArticle

Fatigue-Mediated Loss of Complexity is Contraction-Type Dependent in Vastus Lateralis Electromyographic Signals

Department of Kinesiology and Physical Education, Northern Illinois University, DeKalb, IL 60115, USA
Author to whom correspondence should be addressed.
Sports 2019, 7(4), 78;
Received: 7 March 2019 / Revised: 28 March 2019 / Accepted: 29 March 2019 / Published: 2 April 2019
(This article belongs to the Special Issue The Evaluation of Exercise Using Electromyography)
PDF [1157 KB, uploaded 2 April 2019]


The purpose of this study was to investigate the effect of fatigue status and contraction type on complexity of the surface electromyographic (sEMG) signal. Twelve females (mean age ± SD = 21.1 ± 1.4 years) performed three fatigue-inducing protocols that involved maximal concentric, eccentric, or isometric knee-extensor contractions over three non-consecutive sessions. Pre- and post-fatigue assessments were also completed each session and consisted of three maximal efforts for each type of contraction. Complexity of sEMG signals from the vastus lateralis was assessed using Sample Entropy (SampEn) and Detrended Fluctuation Analysis (DFA) as expressed using the scaling exponent α. The results showed that fatigue decreased (p < 0.05) sEMG complexity as indicated by decreased SampEn (non-fatigued: 1.57 ± 0.22 > fatigued: 1.46 ± 0.25) and increased DFA α (non-fatigued: 1.27 ± 0.26 < fatigued: 1.32 ± 0.23). In addition, sEMG complexity was different among contraction types as indicated by SampEn (concentric: 1.58 ± 0.22 > eccentric: 1.47 ± 0.27 and isometric: 1.50 ± 0.21) and DFA α (concentric: 1.27 ± 0.18 < isometric: 1.32 ± 0.18). Thus, these findings suggested sEMG complexity is affected by fatigue status and contraction type, with the degree of fatigue-mediated loss of complexity dependent on the type of contraction used to elicit fatigue. View Full-Text
Keywords: quadriceps; sEMG; sample entropy; DFA; eccentric; concentric; isometric quadriceps; sEMG; sample entropy; DFA; eccentric; concentric; isometric

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Share & Cite This Article

MDPI and ACS Style

Hernandez, L.R.; Camic, C.L. Fatigue-Mediated Loss of Complexity is Contraction-Type Dependent in Vastus Lateralis Electromyographic Signals. Sports 2019, 7, 78.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Sports EISSN 2075-4663 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top