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Effect of glucose and sodium chloride mouth rinses on neuromuscular fatigue: a preliminary study

Khong TK, Selvanayagam V, Yusof A

Eur J Sport Sci, 2021 Feb;21(2):224-230.
PMID: 32056510 DOI: 10.1080/17461391.2020.1730980

Carbohydrate (CHO) mouth rinse has been shown to improve endurance performance and maintain the central drive of contracting muscles. Salt (NaCl) mouth rinse solution, often used in dentistry to desensitise the oral cavity to pain, could also activate cortical areas of the brain. Hence, the objective of this preliminary study was to investigate whether CHO (glucose) and NaCl mouth rinses could attenuate the reduction in maximum voluntary contraction (MVC) and sustained MVC (sMVC) following an endurance exercise (30-minute cycling at 70% VO2max). Ten subjects (male, age: 22 ± 1 years, weight: 65.3 ± 12.4 kg, height: 164.5 ± 7.5 cm, VO2max: 48.3 ± 6.1 mL kg-1 min-1) completed three trials of 30-minute cycling exercise. In a randomised cross-over study, in each trial, the participants rinsed using either water, 6% glucose, or 6% NaCl solution for 5 s immediately prior to and every 10 min during the cycling exercise. The MVC and sMVC were measured pre and post cycling. Analysis of variance showed significant interaction and time effects for MVC, while for sMVC there was a significant interaction with time and group effects. Both MVC and sMVC were higher post cycling in the glucose and NaCl groups compared to the water group, which suggests that activation of glucose and NaCl oral receptors could better preserve post-exercise force production. This is the first study to show that NaCl mouth rinse can produce a comparable effect on glucose. Hence, mouth rinses may be able to activate other distinct pathways that could attenuate fatigue.

Matched MeSH terms: Muscle Fatigue/drug effects*
Fulltext The impact of work rest scheduling for prolonged standing activity

Rahman IA, Mohamad N, Rohani JM, Zein RM

Ind Health, 2018 Nov 21;56(6):492-499.
PMID: 30210096 DOI: 10.2486/indhealth.2018-0043

Prolonged standing can cause discomfort on the body of the workers and can lead to injury and occupational disease. One of the ergonomic intervention is through improving the work-rest scheduling. The purpose of this study are to identify the fatigue level from the perception of the worker and to investigate the impact of the work-rest scheduling to the standing workers for 12 h working time with a different gender. This study involved two methods which are self-assessment of the worker and direct measurement by using electromyography (EMG). For self-assessment, 80 workers have been interviewed using questionnaire in order to identify the fatigue level. For direct measurement, EMG was attached to the 15 selected workers at their respective leg and lower back to analyse the muscle efforts. In terms of perception, the results show the discomfort and fatigue level at the lower body region in the following order as foot ankle, lower back and leg. There is a significant difference between gender on discomfort pain for foot ankle and leg. The results show short frequent break by 10 min can reduce the fatigue at the leg and infrequent long break is preferable in order to reduce the fatigue at the lower back. In conclusion, it was found that prolonged standing affect the muscle fatigue and discomfort especially lower extremities such as foot ankle, lower back and leg. Besides that, different type of work rest scheduling and gender have significant result towards the muscle fatigue development.

Matched MeSH terms: Muscle Fatigue/physiology*
Towards a Grand Unified Theory of sports performance

Glazier PS

Hum Mov Sci, 2017 Dec;56(Pt A):139-156.
PMID: 26725372 DOI: 10.1016/j.humov.2015.08.001

Sports performance is generally considered to be governed by a range of interacting physiological, biomechanical, and psychological variables, amongst others. Despite sports performance being multi-factorial, however, the majority of performance-oriented sports science research has predominantly been monodisciplinary in nature, presumably due, at least in part, to the lack of a unifying theoretical framework required to integrate the various subdisciplines of sports science. In this target article, I propose a Grand Unified Theory (GUT) of sports performance-and, by elaboration, sports science-based around the constraints framework introduced originally by Newell (1986). A central tenet of this GUT is that, at both the intra- and inter-individual levels of analysis, patterns of coordination and control, which directly determine the performance outcome, emerge from the confluence of interacting organismic, environmental, and task constraints via the formation and self-organisation of coordinative structures. It is suggested that this GUT could be used to: foster interdisciplinary research collaborations; break down the silos that have developed in sports science and restore greater disciplinary balance to the field; promote a more holistic understanding of sports performance across all levels of analysis; increase explanatory power of applied research work; provide stronger rationale for data collection and variable selection; and direct the development of integrated performance monitoring technologies. This GUT could also provide a scientifically rigorous basis for integrating the subdisciplines of sports science in applied sports science support programmes adopted by high-performance agencies and national governing bodies for various individual and team sports.

Matched MeSH terms: Muscle Fatigue/physiology
Fulltext Cognitive stress changes the attributes of the three heads of the triceps brachii during muscle fatigue

Hussain J, Sundaraj K, Subramaniam ID

PLoS One, 2020;15(1):e0228089.
PMID: 31999750 DOI: 10.1371/journal.pone.0228089

INTRODUCTION: Cognitive stress (CS) changes the peripheral attributes of a muscle, but its effect on multi-head muscles has not been investigated. The objective of the current research was to investigate the impact of CS on the three heads of the triceps brachii (TB) muscle.
METHODS: Twenty-five young and healthy university students performed a triceps push-down exercise at 45% one repetition maximum (1RM) with and without CS until task failure, and the rate of fatigue (ROF), endurance time (ET) and number of repetitions (NR) for both exercises were analyzed. In addition, the first and last six repetitions of each exercise were considered non-fatiguing (NF) and fatiguing (Fa), respectively, and the root mean square (RMS), mean power frequency (MPF) and median frequency (MDF) for each exercise repetition were evaluated.
RESULTS: The lateral and long head showed significant differences (P<0.05) in the ROF between the two exercises, and all the heads showed significant (P<0.05) differences in the RMS between the two exercises under NF conditions. Only the long head showed a significant difference (P<0.05) in the MPF and MDF between the two exercises. CS increases the ET (24.74%) and NR (27%) of the exercise. The three heads showed significant differences (P<0.05) in the RMS, MPF and MDF under all exercise conditions.
CONCLUSION: A lower ROF was obtained with CS. In addition, the RMS was found to be better approximator of CS, whereas MPF and MDF were more resistant to the effect of CS. The results showed that the three heads worked independently under all conditions, and the non-synergist and synergist head pairs showed similar behavior under Fa conditions. The findings from this study provide additional insights regarding the functioning of each TB head.

Matched MeSH terms: Muscle Fatigue/physiology*
Fulltext Comparison between two methods of variable resistance training on body composition, muscular strength and functional capacity among untrained males

Amir Bahram Kashiani, Kim, Geok Soh, Kim, Lam Soh, Swee, Leong Ong, Kittichottipanich, Boonsrin

Movement Health & Exercise, 2020;9(1):45-66.
MyJurnal

Several studies have shown a positive association between variable resistance training (VRT) and improvements in muscular performance. However, the effects of VRT on body composition among untrained individuals remain unclear. The objective of this study was to examine the comparison between of methods of VRT on body composition, muscular strength and functional capacity among untrained male adults. Fifty healthy untrained males (age: 21.5 ± 1.95 years) were selected randomly and assigned into three groups: combined weight and chain (WC), combined weight and elastic band (WE), and free-weight (CG). All three groups completed 12 weeks of high intensity resistance training (70-80% of one-repetition maximum) with three sets of 8-12 repetitions two times per week. Approximately 65% of the whole resistance was provided by free-weights, while the other 35% of the resistance was provided by chains and elastic bands for the WC and WE groups, respectively. Dependent variables including body composition, muscular strength and functional capacity using bioelectrical impedance analyzer, one-repetition maximum and maximum repetitions to muscular fatigue were measured, respectively in pre-test, post-test 1 (week 6) and post-test 2. Significance level was set at P < 0.05. No differences existed among all groups at baseline for depended variables. A mixed model ANOVA with repeated measurements analysis revealed that although there were not significant differences in body composition among the groups (P > 0.05), all groups showed a significant reduction in fat mass and significant increase in fat-free mass during and after the intervention (P = 0.0001), and these differences were insignificantly greater in WE and WC groups compared with CG group. Furthermore, all three groups showed significant improvements in muscular strength and functional capacity during and after intervention (P = 0.0001), and muscular strength and functional capacity were greater in WE and WC groups compared with the CG group, but there were not significant differences in muscular strength and functional capacity between WE and WC groups. However, the WE group showed insignificantly more improvement in muscular strength and functional capacity compared with the WC group during and after the intervention. The results of this study show that VRT has a slightly better effect than free-weight to improve body composition during and after 12 weeks intervention. Also, WE training had a slightly better effect than WC training in improving muscular strength and functional capacity during and after 12 weeks of VRT among untrained male adults.

Matched MeSH terms: Muscle Fatigue
Fulltext Muscle Fatigue in the Three Heads of the Triceps Brachii During a Controlled Forceful Hand Grip Task with Full Elbow Extension Using Surface Electromyography

Ali A, Sundaraj K, Badlishah Ahmad R, Ahamed NU, Islam A, Sundaraj S

J Hum Kinet, 2015 Jun 27;46:69-76.
PMID: 26240650 DOI: 10.1515/hukin-2015-0035

The objective of the present study was to investigate the time to fatigue and compare the fatiguing condition among the three heads of the triceps brachii muscle using surface electromyography during an isometric contraction of a controlled forceful hand grip task with full elbow extension. Eighteen healthy subjects concurrently performed a single 90 s isometric contraction of a controlled forceful hand grip task and full elbow extension. Surface electromyographic signals from the lateral, long and medial heads of the triceps brachii muscle were recorded during the task for each subject. The changes in muscle activity among the three heads of triceps brachii were measured by the root mean square values for every 5 s period throughout the total contraction period. The root mean square values were then analysed to determine the fatiguing condition for the heads of triceps brachii muscle. Muscle fatigue in the long, lateral, and medial heads of the triceps brachii started at 40 s, 50 s, and 65 s during the prolonged contraction, respectively. The highest fatiguing rate was observed in the long head (slope = -2.863), followed by the medial head (slope = -2.412) and the lateral head (slope = -1.877) of the triceps brachii muscle. The results of the present study concurs with previous findings that the three heads of the triceps brachii muscle do not work as a single unit, and the fiber type/composition is different among the three heads.

Matched MeSH terms: Muscle Fatigue
Branched-chain amino acid supplementation improves cycling performance in untrained cyclists

Manaf FA, Peiffer JJ, Maker GL, Fairchild TJ

J Sci Med Sport, 2021 Apr;24(4):412-417.
PMID: 33162329 DOI: 10.1016/j.jsams.2020.10.014

OBJECTIVES: To investigate the effects of acute branched-chain amino acid (BCAA) supplementation on cycling performance and neuromuscular fatigue during a prolonged, self-paced cycling time-trial.
DESIGN: Randomised double-blind counterbalanced crossover.
METHODS: Eighteen recreationally active men (mean±SD; age: 24.7±4.8 years old; body-weight, BW: 67.1±6.1kg; height: 171.7±4.9cm) performed a cycling time-trial on an electromagnetically-braked cycle ergometer. Participants were instructed to complete the individualised total work in the shortest time possible, while ingesting either BCAAs (pre-exercise: 0.084gkg-1 BW; during exercise: 0.056gkg-1h-1) or a non-caloric placebo solution. Rating of perceived exertion, power, cadence and heart rate were recorded throughout, while maximal voluntary contraction, muscle voluntary activation level and electrically evoked torque using single and doublet stimulations were assessed at baseline, immediately post-exercise and 20-min post-exercise.
RESULTS: Supplementation with BCAA reduced (287.9±549.7s; p=0.04) time-to-completion and ratings of perceived exertion (p≤0.01), while concomitantly increasing heart rate (p=0.02). There were no between-group differences (BCAA vs placebo) in any of the neuromuscular parameters, but significant decreases (All p≤0.01) in maximal voluntary contraction, muscle voluntary activation level and electrically evoked torque (single and doublet stimulations) were recorded immediately following the trial, and these did not recover to pre-exercise values by the 20min recovery time-point.
CONCLUSIONS: Compared to a non-caloric placebo, acute BCAA supplementation significantly improved performance in cycling time-trial among recreationally active individuals without any notable changes in either central or peripheral factors. This improved performance with acute BCAA supplementation was associated with a reduced rating of perceived exertion.

Matched MeSH terms: Muscle Fatigue/drug effects*
Role of carbohydrate in central fatigue: a systematic review

Khong TK, Selvanayagam VS, Sidhu SK, Yusof A

Scand J Med Sci Sports, 2017 Apr;27(4):376-384.
PMID: 27714855 DOI: 10.1111/sms.12754

Carbohydrate (CHO) depletion is linked to neuromuscular fatigue during exercise. While its role at peripheral level is relatively well understood, less is known about its impact centrally. The aim of this systematic review was to critically analyze the effects of CHO on central fatigue (CF) assessed by various neurophysiological techniques. Four databases were searched using PRISMA guidelines through February 2016. The inclusion criteria were: CHO as intervention against a placebo control, fatigue induced by prolonged exercise and assessed using neurophysiological measures [voluntary activation (VA), superimposed twitch (SIT), M-wave, electromyography], alongside maximal voluntary contraction (MVC). Seven papers were reviewed, where exercise duration lasted between 115 and 180 min. CHO improved exercise performance in three studies, whereby two of them attributed it to CF via attenuation of VA and SIT reductions, while the other indicated peripheral involvement via attenuation of M-wave reduction. Although a few studies suggest that CHO attenuates CF, data on its direct effects on neurophysiological outcome measures are limited and mixed. Generally, measures employed in these studies were inadequate to conclude central contribution to fatigue. Factors including the techniques used and the lack of controls render additional confounding factors to make definitive deductions. Future studies should employ consistent techniques and appropriate neurophysiological controls to distinguish CHO effect at central level. The use of pharmacological intervention should be incorporated to elucidate involvement of central mechanisms.

Matched MeSH terms: Muscle Fatigue