Special Issue "The Evaluation of Exercise Using Electromyography"

A special issue of Sports (ISSN 2075-4663).

Deadline for manuscript submissions: 31 October 2019

Special Issue Editor

Guest Editor
Assoc. Prof. Clayton L. Camic, Ph.D.

Kinesiology and Physical Education, 228 Anderson Hall, Northern Illinois University, DeKalb, Illinois 60115, USA
Website | E-Mail
Interests: nutritional supplements; ergogenic aids; electromyography; muscle fatigue

Special Issue Information

Dear Colleagues,

Electromyography is a diverse tool used to evaluate neuromuscular function through the analysis of the electrical activity of contracting skeletal muscle fibers. Specifically, the electromyographic signal provides global information related to the action potentials of the motor units within the pickup range of the recording electrodes. This technique is widely utilized across many fields, with therapeutic, clinical, and human performance applications.

The electromyographic technique is commonly used to examine changes in muscle activation during various forms of static (e.g., isometric muscle actions) and dynamic (e.g., cycling, running, isolated concentric and eccentric muscle actions) exercise. For example, electromyographic responses from active muscle reflect the motor control strategies (i.e., motor unit recruitment, motor unit firing rates, motor unit synchronization) associated with changes in force production and the development of fatigue specific to a given task.  

The aim of this Special Issue is to deliver new insight into the use of electromyography to assess neuromuscular function during exercise and promote novel applications. We hope that this knowledge will help provide coaches, clinicians, and other health and sport professionals with valuable information that can be used to establish new training methods, therapeutic strategies, and assessment techniques.

Prof. Clayton L. Camic, Ph.D.
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sports is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 350 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • electromyography
  • neuromuscular function
  • neuromuscular fatigue
  • muscle activation
  • exercise
  • sports performance
  • motor control strategies
  • motor unit recruitment
  • motor unit firing rates

Published Papers (3 papers)

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Research

Open AccessFeature PaperArticle
Fatigue-Mediated Loss of Complexity is Contraction-Type Dependent in Vastus Lateralis Electromyographic Signals
Received: 7 March 2019 / Revised: 28 March 2019 / Accepted: 29 March 2019 / Published: 2 April 2019
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Abstract
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, [...] Read more.
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. Full article
(This article belongs to the Special Issue The Evaluation of Exercise Using Electromyography)
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Open AccessArticle
Thinking Outside the Block: External Focus of Attention Improves Reaction Times and Movement Preparation Times in Collegiate Track Sprinters
Received: 1 September 2018 / Revised: 11 October 2018 / Accepted: 17 October 2018 / Published: 19 October 2018
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Abstract
While focusing attention on external cues (EF) has been shown to enhance performance track and field coaches tend to provide instructions that promote internal focus of attention (IF) during block starts. The aims of this study were to determine: (1) whether promoting EF [...] Read more.
While focusing attention on external cues (EF) has been shown to enhance performance track and field coaches tend to provide instructions that promote internal focus of attention (IF) during block starts. The aims of this study were to determine: (1) whether promoting EF versus IF would improve reaction time (RT) of sprinters, and (2) if changes occur at the level of central processes during movement preparation (premotor RT) or peripheral processes during movement execution (motor RT). Twelve collegiate track sprinters (age 20.8 ± 1.7) completed three testing sessions under EF, IF, and no focus instruction (NF) conditions. RT was recorded from the left and right blocks. Muscle activation time (EMG) was recorded from the vastus lateralis and gastrocnemius muscles. Mean rear foot RT was significantly shorter (p < 0.0001) under the EF (212.11 ms) compared with the IF (234.21 ms) and NF conditions (236.87 ms). Front foot RT was significantly shorter (p < 0.05) during EF (250.24 ms), compared to IF (266.98 ms) but not shorter than the NF (268.73 ms) condition. Mean premotor RT under the EF condition (157.75 ms) was significantly shorter (p < 0.001) compared with the IF (181.90 ms) and NF (173.60 ms) conditions. No differences were found in motor RT across conditions (p > 0.05). Adopting an EF improves RT during sprint starts. This improvement likely originates from a shortening in movement preparation time, as opposed to a faster excitation contraction coupling of the muscle fibers. These findings could potentially contribute to the development of new coaching methods aimed at improving the starting technique of athletes. Full article
(This article belongs to the Special Issue The Evaluation of Exercise Using Electromyography)
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Open AccessArticle
Co-Activation, Estimated Anterior and Posterior Cruciate Ligament Forces, and Motor Unit Activation Strategies during the Time Course of Fatigue
Received: 31 July 2018 / Revised: 14 September 2018 / Accepted: 18 September 2018 / Published: 21 September 2018
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Abstract
This study aimed to combine co-activation as well as anterior and posterior cruciate ligament force estimations with the motor unit activation strategies employed by the primary muscles that are involved in the movement at the knee joint. Fourteen male subject performed 25 maximal [...] Read more.
This study aimed to combine co-activation as well as anterior and posterior cruciate ligament force estimations with the motor unit activation strategies employed by the primary muscles that are involved in the movement at the knee joint. Fourteen male subject performed 25 maximal concentric isokinetic leg extension muscle actions at 120 s−1. Electromyographic and mechanomyographic signals from the vastus lateralis and bicep femoris, as well as force, were used to measure co-activation, and estimated anterior and posterior ligament forces during the time course of fatigue. There were decreases in quadriceps force and increases in hamstring force during the 25 leg extensions. The posterior cruciate ligament force was greater than the anterior cruciate ligament force during each leg extension. Both the posterior and anterior cruciate ligament forces decreased during the 25 leg extensions. Each muscle indicated unique neuromuscular responses, which may explain the decreases in quadriceps force and increases in the hamstring force. The combination of anterior and posterior cruciate ligament force estimation and motor unit activation strategies helped to provide a better understanding of the fatigue-related mechanism that was utilized to avoid injury and increase or maintain joint stability during the time course of fatigue. Full article
(This article belongs to the Special Issue The Evaluation of Exercise Using Electromyography)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. The Effects Of Attentional Focus On Power Production During Bench-Press

    Attila J. Kovacs, Jonathan R. Flintchum, Michael Schiller, Clayton L. Camic

Abstract: Over the past decade a growing body of literature has demonstrated the benefits of an external focus of attention compared to an internal focus of attention during motor performance. This pattern of results has been explained by the constrained action hypothesis, whereby adopting an external focus of attention allows the system to self-organize, resulting in more efficient and automated motor performance and learning. While many studies focused on the effects of different attentional foci during skill acquisition, relatively few studies have been reported investigating these effects on skill performance using a well-learned dynamic task. Therefore, the purpose of this study was to compare muscle power production during a bench-press task under different foci of attention conditions. Participants (n = 26; age 18-22) were undergraduate students/athletes that have been regularly performing weightlifting activities two times a week, for a minimum of one year. Following a standardized warm-up, participants completed five repetitions of bench press at 45% load of their one repetition maximum (1RM) using a Smith machine. Power output was recorded by a MyotestPro device attached to the barbell. The task required participants to propel the barbell with weights as high and as fast as possible. Power output was assessed under three different conditions: external focusing instructions (EF) required to focus attention on the barbell and to try to propel it as high as possible; internal focusing instructions (IF) required to focus attention on contracting the pectoral muscles during the task; and no focusing (NF) condition in which participants did not receive any type of instruction. Data analysis, using repeated measures ANOVAs, indicated significant (P < 0.05) differences among conditions. Power production was significantly greater under the EF condition compared to the IF condition, while performances under IF and NF conditions were not different. Additionally, there was a significant decrease in muscle activation (EMG RMS) for the triceps brachii muscle under the EF condition, compared with the IF and NF conditions. This pattern of reduced muscle activation and higher power output suggests that adopting an EF might improve the efficiency movement control during dynamic movements. Conversely, lower power output, and increased muscle activation of the pectoralis major was detected under the IF condition compared with the EF and NF conditions. These findings might be considered when designing training protocols for athletes with the purpose of maximizing their power production.

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