The Role of the Nervous System in Neuromuscular Fatigue Induced by Ultra-Endurance Exercise

Ultra-endurance events are not a recent development but they have only become very popular in the last two decades, particularly ultra-marathons run on trails. The present paper reviews the role of the central nervous system (CNS) in neuromuscular fatigue induced by ultra-endurance exercise. Large decreases in voluntary activation are systematically found in ultra-endurance running but are attenuated in ultra-endurance cycling for comparable intensity and duration. This indirectly suggests that afferent feedback, rather than neurobiological changes within the CNS, is determinant in the amount of central fatigue produced. Whether this is due to inhibition from type III and IV afferent fibres induced by inflammation, disfacilitation of Ia afferent fibers due to repeated muscle stretching or other mechanisms still needs to be determined. Sleep deprivation per se does not seem to play a significant role in central fatigue although it still affects performance by elevating ratings of perceived exertion. The kinetics of central fatigue and recovery, the influence of muscle group (knee extensors vs plantar flexors) on central deficit as well as the limitations related to studies on central fatigue in ultra-endurance exercise are also discussed in the present article. To date, no study has quantified the contribution of spinal modulations to central fatigue in ultra-endurance events. Future investigations utilizing spinal stimulation (i.e. thoracic stimulation) must be conducted to assess the role of changes in motoneuronal excitability on the observed central fatigue. Recovery after ultra-endurance events and the effect of sex on neuromuscular fatigue must also be studied further

Resting and active motor thresholds versus stimulus–response curves to determine transcranial magnetic stimulation intensity in quadriceps femoris

Background: Transcranial magnetic stimulation (TMS) is a widely-used investigative technique in motor cortical evaluation. Recently, there has been a surge in TMS studies evaluating lower-limb fatigue. TMS intensity of 120-130% resting motor threshold (RMT) and 120% active motor threshold (AMT) and TMS intensity determined using stimulus-response curves during muscular contraction have been used in these studies. With the expansion of fatigue research in locomotion, the quadriceps femoris is increasingly of interest. It is important to select a stimulus intensity appropriate to evaluate the variables, including voluntary activation, being measured in this functionally important muscle group. This study assessed whether selected quadriceps TMS stimulus intensity determined by frequently employed methods is similar between methods and muscles.Methods: Stimulus intensity in vastus lateralis, rectus femoris and vastus medialis muscles was determined by RMT, AMT (i.e. during brief voluntary contractions at 10% maximal voluntary force, MVC) and maximal motor-evoked potential (MEP) amplitude from stimulus-response curves during brief voluntary contractions at 10, 20 and 50% MVC at different stimulus intensities.Results: Stimulus intensity determined from a 10% MVC stimulus-response curve and at 120 and 130% RMT was higher than stimulus intensity at 120% AMT (lowest) and from a 50% MVC stimulus-response curve (p 0.05).Conclusions: Similar optimal stimulus intensity and maximal MEP amplitudes at 20 and 50% MVC and the minimal risk of residual fatigue at 20% MVC suggest that a 20% MVC stimulus-response curve is appropriate for determining TMS stimulus intensity in the quadriceps femoris. The higher selected stimulus intensities at 120-130% RMT have the potential to cause increased coactivation and discomfort and the lower stimulus intensity at 120% AMT may underestimate evoked responses. One muscle may also act as a surrogate in determining optimal quadriceps femoris stimulation intensity

FRONTCRAWL PROPULSIVE PHASE DETECTION USING INERTIAL SENSORS

Front crawl is an alternating swimming stroke technique in which different phases of arm movement induce changes in acceleration of limbs and body. This study proposes a new approach to use inertial body worn sensors to estimate main temporal phases of front crawl. Distinctive features in kinematic signals are used to detect the temporal phases. These temporal phases are key information sources of qualitative and quantitative evaluation of swimming coordination, which have been assessed previously by video analysis. The present method has been evaluated upon a wide range of coordination and showed a difference of 4.9% with video based system. The results are in line with video analysis inter-operator variability yet offering an easy-to-use system for trainers

Therapeutic potential of fatty acid amide hydrolase, monoacylglycerol lipase, and N-acylethanolamine acid amidase inhibitors

Fatty acid ethanolamides (FAEs) and endocannabinoids (ECs) have been shown to alleviate pain and inflammation, regulate motility and appetite, and produce anti-cancer, anxiolytic, and neuroprotective efficacies via cannabinoid receptor type 1 (CB1) or type 2 (CB2), or via peroxisome proliferator-activated receptor α (PPAR-α) stimulation. FAEs and ECs are synthesized by a series of endogenous enzymes, including N acylphosphatidylethanolamine-phospholipase D (NAPE-PLD), diacylglycerol lipase (DAGL), or phospholipase C (PLC), and their metabolism is mediated by several metabolic enzymes, including fatty acid amide hydrolase (FAAH), monoacylglycerol lipase (MAGL), Nacylethanolamine acid amidase (NAAA), or cyclooxygenase-2 (COX-2). Over the last decades, increasing the concentration of FAEs and ECs through the inhibition of degrading enzymes has been considered to be a viable therapeutic approach to enhance their anti-nociceptive and anti-inflammatory effects, as well as protecting the nervous system

Utilisation de la stimulation magnétique transcrânienne dans l'évaluation de la fonction motrice (aspects méthodologiques et application à l'exercice extrême)

La stimulation magnétique transcrânienne (TMS) est une technique d'investigation classiquement utilisée dans l'évaluation du cortex moteur. La TMS est utilisée dans l'étude de la fatigue afin de distinguer sa composante centrale. Peu d'études ont utilisé cette technique pour évaluer les effets de l'exercice locomoteur et aucune dans des conditions extrêmes. Ainsi, l'objectif de cette thèse était double: d'abord, répondre à certaines questions méthodologiques concernant l'utilisation de la TMS dans l'évaluation de la fatigue, en particulier du muscle quadriceps, et deuxièmement, étudier les effets de l'exercice en conditions extrêmes sur le développement de la fatigue centrale et supraspinal ainsi que sur l excitabilité et l'inhibition corticospinales. Dans les Etudes 1 et 2, l'effet de différentes approches d'une force cible avant l application d'une impulsion TMS ainsi que les différences entre les principales méthodes utilisées pour déterminer l'intensité optimale de TMS ont été étudiés. Dans l'Etude 3, l'effet d'une nuit de privation de sommeil sur les performances cognitives et physiques et les paramètres centraux a été étudié. L'effet d'un ultra-trail de 110 km sur la composante supraspinale de la fatigue centrale a été évalué dans l'Etude 4. Les conclusions principales de cette thèse sont, sur le plan méthodologique, i) que lors de l'évaluation par TMS pendant de brèves contractions volontaires, il est essentiel d appliquer l'impulsion de TMS après que la force produite par le sujet se soit stabilisée à la valeur cible et ii) qu'une courbe stimulus-réponse à 20% de la force maximale volontaire est appropriée pour déterminer l'intensité de TMS optimale dans les études portant sur l'exercice et la fatigue. De plus, bien que la privation de sommeil ait des impacts négatifs sur les performances cognitives et à l'exercice, elle n'a pas d'influence sur des paramètres neuromusculaires ni ne provoque une plus grande fatigue centrale. Une fatigue supraspinale se développe et l excitabilité corticospinale augmente au cours d exercices d'endurance/ultra-endurance en course à pied et ne vélo, tandis que les effets sur les mécanismes inhibiteurs corticospinaux sont équivoques et probablement dépendent des caractéristiques de l'exercice et de l'intensité de la TMSTranscranial magnetic stimulation (TMS) is a widely-used investigative technique in motor cortical evaluation. TMS is now being used in the investigation of fatigue to help partition the effects of central fatigue. Few studies have utilized this technique to evaluate the effects of locomotor exercise and none in conditions of extreme exercise. Therefore, the purpose of this thesis was twofold; first, to answer methodological questions pertaining to the use of TMS in fatigue evaluation, particularly of the quadriceps, and second, to investigate the effects of extreme exercise conditions on the development of central and supraspinal fatigue and corticospinal excitability and inhibition. In Studies 1 and 2, the effect of approaching a target force in different ways before the delivery a TMS pulse and the difference between commonly-employed methods of determining TMS intensity on the selection of optimal TMS intensity were investigated. In Study 3, the effect of one night sleep deprivation on cognitive and exercise performance and central parameters was investigated. The effect of a 110-km ultra-trail on the supraspinal component of central fatigue was evaluated in Study 4. The principal findings from this thesis are that during TMS evaluation during brief voluntary contractions, it is essential to deliver the TMS pulse once the force has stabilized at the target and that a stimulus-response curve at 20% MVC is appropriate for determining optimal TMS intensity in exercise and fatigue studies. Furthermore, while sleep deprivation negatively-impacted cognitive and exercise performance, it did not influence neuromuscular parameters nor result in greater central fatigue. Supraspinal fatigue develops and corticospinal excitability increases during endurance/ultra-endurance running and cycling, while the effects on inhibitory corticospinal mechanisms are equivocal and probably depend on exercise characteristics and TMS intensityST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF

A Student Parent Assistance Pilot Program for Incoming Associate Degree Students

This Student Parent Assistance Pilot Program engaged family members to support their students in adapting to the academic challenges of entering college. Materials were constructed so that family members did not have to be knowledgeable in the course content in order to assist their students. Outcomes indicated that participating students and their family members had a more positive view of the program than did a non-participating comparison student group. A student vignette is used to illustrate the students’ positive view of the program

New horizons for the methodology and physiology of training periodization: Block Periodization: New horizon or a false dawn?

It would appear premature to herald block periodization as a ‘new horizon’ in training planning, partly because of a fundamental lack of supporting evidence and clearly delineated rationale, and partly because contradictory evidence exists questioning its universal efficacy in elite contexts. What block periodization does positively contribute to current planning methodologies is a more formal description of a particular planning tactic that may be advantageously added to the elite coaches menu of potential planning options. Therefore, while blocked-training schemes may be useful ploys in specific training contexts, the claim that this framework represents a new departure in training planning may be somewhat overly enthusiastic. Hence, perhaps a more appropriate description of block periodization is ‘new variation’, rather than a ‘new horizon’, in sports training planning

Use of transcranial magnetic stimulation to assess relaxation rates in unfatigued and fatigued knee-extensor muscles

We examined whether transcranial magnetic stimulation (TMS) delivered to the motor cortex 13 allows assessment of muscle relaxation rates in unfatigued and fatigued knee extensors (KE). 14 We assessed the ability of this technique to measure time course of fatigue-induced changes 15 in muscle relaxation rate and compared relaxation rate from resting twitches evoked by 16 femoral nerve stimulation. Twelve healthy men performed maximal voluntary isometric 17 contractions (MVC) twice before (PRE) and once at the end of a 2-min KE MVC and five 18 more times within 8 min during recovery. Relative (intraclass correlation coefficient; ICC2,1) 19 and absolute (repeatability coefficient) reliability and variability (coefficient of variation) 20 were assessed. Time course of fatigue-induced changes in muscle relaxation rate was tested 21 with generalized estimating equations. In unfatigued KE, peak relaxation rate coefficient of 22 variation and repeatability coefficient were similar for both techniques. Mean (95% CI) 23 ICC2,1 for peak relaxation rates were [0.933 (0.724-0.982)] and [0.889 (0.603-0.968)] for 24 TMS and femoral nerve stimulation, respectively. TMS-induced normalized muscle 25 relaxation rate was -11.5 ± 2.5 s-1 at PRE, decreased to -6.9 ± 1.2 s-1 (-37 ± 17%, P < 0.001), 26 and recovered by 2 min post-exercise. Normalized peak relaxation rate for resting twitch did 27 not show a fatigue-induced change. During fatiguing KE exercise, the change in muscle 28 relaxation rate as determined by the two techniques was different. TMS provides reliable 29 values of muscle relaxation rates. Furthermore, it is sufficiently sensitive and more 30 appropriate than the resting twitch evoked by femoral nerve stimulation to reveal fatigue-31 induced changes in KE