Neuromuscular and Perceptual Responses to Sub-Maximal Eccentric Cycling

ObjectiveEccentric (ECC) cycle-ergometers have recently become commercially-available, offering a novel method for rehabilitation training. Many studies have reported that ECC cycling enables the development of higher levels of muscular force at lower cardiorespiratory and metabolic loads, leading to greater force enhancements after a training period. However, fewer studies have focused on the specific perceptual and neuromuscular changes. As the two latter aspects are of major interest in clinical settings, this review aimed to present an overview of the current literature centered on the neuromuscular and perceptual responses to submaximal ECC cycling in comparison to concentric (CON) cycling.DesignNarrative review of the literature.ResultsAt a given mechanical workload, muscle activation is lower in ECC than in CON while the characteristics of the musculo-articular system (i.e., muscle-tendon unit, fascicle, and tendinous tissue length) are quite similar. At a given heart rate or oxygen consumption, ECC cycling training results in greater muscular hypertrophy and strength gains than CON cycling. On the contrary, CON cycling training seems to enhance more markers of muscle aerobic metabolism than ECC cycling performed at the same heart rate intensity. Data concerning perceptual responses, and neuromuscular mechanisms leading to a lower muscle activation (i.e., neural commands from cortex to muscular system) at a given mechanical workload are scarce.ConclusionEven though ECC cycling appears to be a very useful tool for rehabilitation purposes the perceptual and neural commands from cortex to muscular system during exercise need to be further studied

Neuromuscular alterations induced by fatiguing eccentric and concentric exercises : emphasis on eccentric cycling

L’effet du mode de contraction musculaire dynamique (concentrique ou excentrique) sur la fatigabilité fonctionnelle et les altérations neuromusculaires associées reste à explorer. Le mode de contraction musculaire interagit avec d’autres caractéristiques d’exercice, telles que l’intensité (maximale ; sous-maximale) ou la modalité (mono-articulaire ; locomoteur). Ce travail de thèse a comparé l’impact d’exercices excentriques et concentriques sur la fonction neuromusculaire au niveau des extenseurs du genou, à travers trois études. Nous avons montré que, pour la réalisation d’un même travail mécanique, les deux modes de contraction musculaire affectaient autant le moment maximal volontaire isométrique. En revanche, l’origine des perturbations (nerveuses/musculaires) dépendaient des caractéristiques de l’exercice. Dans l’étude 1, des contractions mono-articulaires excentriques à intensité maximale affectaient la fonction nerveuse mais pas contractile, alors que des contractions concentriques avaient l’effet inverse. Dans l’étude 2, des exercices de pédalage excentrique et concentrique à la même puissance sous-maximale causaient des altérations neuromusculaires semblables, à l’exception d’une perturbation du couplage excitation-contraction après le pédalage excentrique. En comparant les résultats de ces deux études avec la littérature, il semble que le mode de contraction musculaire n’influence les perturbations neuromusculaires après l’exercice que pour des exercices maximaux. L’étude 3, n’a rapporté aucun changement du contrôle nerveux du pédalage concentrique ou excentrique au cours d’un exercice fatigant. Néanmoins, l’excitabilité corticospinale vers les muscles extenseurs du genou était moindre et l’inhibition relative supérieure lors du pédalage excentrique en comparaison du concentrique. Dans leur ensemble, ces résultats précisent les effets des contractions excentriques sur la fonction neuromusculaire et offrent de nombreuses perspectives d’études. Notamment les mécanismes responsables de l’inhibition corticospinale relative pendant le pédalage excentrique peuvent être sondés par stimulations transcrâniennes et de la voie pyramidale pendant la période de silence.The influence of dynamic contraction type (concentric or eccentric) on performance fatigability and associated neuromuscular alterations is partly unknown. Contraction type interacts with other exercise features such as intensity (maximal; submaximal) or modality (single-joint; locomotor). Thus, we compared eccentric with concentric exercises of similar characteristics across three experimental studies. We showed that, for the completion of a given amount of mechanical work, both contraction types impaired maximal voluntary isometric torque similarly. However, neuromuscular impairments depended on exercise features. In study 1, maximal single-joint eccentric contractions affected neural but not contractile function, and concentric exercises exhibited the opposite effect. In study 2, eccentric and concentric cycling at the same power output caused similar neuromuscular alterations, apart from an impairment of the excitation-contraction coupling process after eccentric cycling only. Along with the literature, these two studies suggest that contraction type only affects post-exercise neuromuscular perturbations when exercise intensity is maximal. Study 3 showed no change in the neural control of pedaling during fatiguing concentric or eccentric cycling at the same power output. Yet we found a greater excitability and relative inhibition of the corticospinal pathway to the knee extensor muscles, during concentric compared with eccentric cycling, respectively. Overall, these results provide specifications on the effects of eccentric contractions on neuromuscular function et offer research perspectives. Notably, the processes underpinning the relative corticospinal inhibition during eccentric cycling may be investigated by applying transcranial and pyramidal tract stimulations during the silent period

Altérations neuromusculaires induites par des exercices excentriques et concentriques fatigants : emphase sur le pédalage des membres inférieurs

The influence of dynamic contraction type (concentric or eccentric) on performance fatigability and associated neuromuscular alterations is partly unknown. Contraction type interacts with other exercise features such as intensity (maximal; submaximal) or modality (single-joint; locomotor). Thus, we compared eccentric with concentric exercises of similar characteristics across three experimental studies. We showed that, for the completion of a given amount of mechanical work, both contraction types impaired maximal voluntary isometric torque similarly. However, neuromuscular impairments depended on exercise features. In study 1, maximal single-joint eccentric contractions affected neural but not contractile function, and concentric exercises exhibited the opposite effect. In study 2, eccentric and concentric cycling at the same power output caused similar neuromuscular alterations, apart from an impairment of the excitation-contraction coupling process after eccentric cycling only. Along with the literature, these two studies suggest that contraction type only affects post-exercise neuromuscular perturbations when exercise intensity is maximal. Study 3 showed no change in the neural control of pedaling during fatiguing concentric or eccentric cycling at the same power output. Yet we found a greater excitability and relative inhibition of the corticospinal pathway to the knee extensor muscles, during concentric compared with eccentric cycling, respectively. Overall, these results provide specifications on the effects of eccentric contractions on neuromuscular function et offer research perspectives. Notably, the processes underpinning the relative corticospinal inhibition during eccentric cycling may be investigated by applying transcranial and pyramidal tract stimulations during the silent period.L’effet du mode de contraction musculaire dynamique (concentrique ou excentrique) sur la fatigabilité fonctionnelle et les altérations neuromusculaires associées reste à explorer. Le mode de contraction musculaire interagit avec d’autres caractéristiques d’exercice, telles que l’intensité (maximale ; sous-maximale) ou la modalité (mono-articulaire ; locomoteur). Ce travail de thèse a comparé l’impact d’exercices excentriques et concentriques sur la fonction neuromusculaire au niveau des extenseurs du genou, à travers trois études. Nous avons montré que, pour la réalisation d’un même travail mécanique, les deux modes de contraction musculaire affectaient autant le moment maximal volontaire isométrique. En revanche, l’origine des perturbations (nerveuses/musculaires) dépendaient des caractéristiques de l’exercice. Dans l’étude 1, des contractions mono-articulaires excentriques à intensité maximale affectaient la fonction nerveuse mais pas contractile, alors que des contractions concentriques avaient l’effet inverse. Dans l’étude 2, des exercices de pédalage excentrique et concentrique à la même puissance sous-maximale causaient des altérations neuromusculaires semblables, à l’exception d’une perturbation du couplage excitation-contraction après le pédalage excentrique. En comparant les résultats de ces deux études avec la littérature, il semble que le mode de contraction musculaire n’influence les perturbations neuromusculaires après l’exercice que pour des exercices maximaux. L’étude 3, n’a rapporté aucun changement du contrôle nerveux du pédalage concentrique ou excentrique au cours d’un exercice fatigant. Néanmoins, l’excitabilité corticospinale vers les muscles extenseurs du genou était moindre et l’inhibition relative supérieure lors du pédalage excentrique en comparaison du concentrique. Dans leur ensemble, ces résultats précisent les effets des contractions excentriques sur la fonction neuromusculaire et offrent de nombreuses perspectives d’études. Notamment les mécanismes responsables de l’inhibition corticospinale relative pendant le pédalage excentrique peuvent être sondés par stimulations transcrâniennes et de la voie pyramidale pendant la période de silence

V̇ o 2peak is of great interest for clinical purposes

International audienc

Effect of Cycling Cadence on Neuromuscular Function: A Systematic Review of Acute and Chronic Alterations

There is a wide range of cadence available to cyclists to produce power, yet they choose to pedal across a narrow one. While neuromuscular alterations during a pedaling bout at non-preferred cadences were previously reviewed, modifications subsequent to one fatiguing session or training intervention have not been focused on. We performed a systematic literature search of PubMed and Web of Science up to the end of 2020. Thirteen relevant articles were identified, among which eleven focused on fatigability and two on training intervention. Cadences were mainly defined as “low” and “high” compared with a range of freely chosen cadences for given power output. However, the heterogeneity of selected cadences, neuromuscular assessment methodology, and selected population makes the comparison between the studies complicated. Even though cycling at a high cadence and high intensity impaired more neuromuscular function and performance than low-cadence cycling, it remains unclear if cycling cadence plays a role in the onset of fatigue. Research concerning the effect of training at non-preferred cadences on neuromuscular adaptation allows us to encourage the use of various training stimuli but not to say whether a range of cadences favors subsequent neuromuscular performance

Corticospinal excitability is altered similarly following concentric and eccentric maximal contractions

International audiencePurpose To examine corticospinal excitability and neuromuscular function following the completion of eccentric (ECC) or concentric (CON) maximal exercises of same mechanical work. Methods Ten males (29.9 +/- 11.8 years) performed maximal isokinetic knee extensor contractions in four experimental sessions. The two first sessions (one in ECC and one in CON) ended with a dynamic peak torque loss of 20%. The work completed in each contraction type was then achieved in the other contraction type. Neuromuscular function- maximal voluntary isometric contraction (MVIC), voluntary activation level (VAL), potentiated doublet (Dt), M-wave- and corticospinal excitability- motor evoked potential (MEP) amplitude and silent period (SP)-were assessed in the vastus lateralis (VL) and rectus femoris (RF) muscles at 20% MVIC before and immediately after exercise. Results To lose 20% of dynamic peak torque subjects performed 1.8 times more work in ECC than CON (P = 0.03), inducing a non-different decline in MVIC (P = 0.15). VAL dropped after the ECC sessions only (- 8.5 +/- 6.7%; all P 0.45), irrespective of contraction type (all P > 0.15). Conclusion Same-work maximal ECC and CON exercises induced similar fatigue level but from different origins (preferentially central for ECC vs peripheral for CON). Yet, net corticospinal excitability did not depend on contraction type

Cartographie des habitats naturels des estrans et zones humides littorales

A l’interface entre terre et mer, les zones humides littorales sont des environnements dont le fonctionnement écosystémique est contraint par les forçages climatiques et anthropiques. Par le biais des directives européennes et des plans de gestion, ces milieux sont suivis et cartographiés à échéance régulière dans le but d’asseoir leur état écologique. Différentes stratégies de cartographie basées sur l’exploitation d’images satellite sont adoptées selon les objectifs à atteindre : (1) cartographie exhaustive des faciès/habitats intertidaux (type Natura 2000), (2) cartographie de l’herbier à Zostera noltii (Directive Cadre sur l’Eau), (3) cartographie des habitats des prés-salés, (4) suivi de l’évolution naturelle des paysages et de la végétation en lien avec des événements accidentels ou volontaires (actions de dépoldérisation)

Increasing polarity in tacrine and huprine derivatives: Potent anticholinesterase agents for the treatment of myasthenia gravis

Symptomatic treatment of myasthenia gravis is based on the use of peripherally-acting acetylcholinesterase (AChE) inhibitors that, in some cases, must be discontinued due to the occurrence of a number of side-effects. Thus, new AChE inhibitors are being developed and investigated for their potential use against this disease. Here, we have explored two alternative approaches to get access to peripherally-acting AChE inhibitors as new agents against myasthenia gravis, by structural modification of the brain permeable anti-Alzheimer AChE inhibitors tacrine, 6-chlorotacrine, and huprine Y. Both quaternization upon methylation of the quinoline nitrogen atom, and tethering of a triazole ring, with, in some cases, the additional incorporation of a polyphenol-like moiety, result in more polar compounds with higher inhibitory activity against human AChE (up to 190-fold) and butyrylcholinesterase (up to 40-fold) than pyridostigmine, the standard drug for symptomatic treatment of myasthenia gravis. The novel compounds are furthermore devoid of brain permeability, thereby emerging as interesting leads against myasthenia gravis