Recent data on cellular component turnover: Focus on adaptations to physical exercise

Significant progress has expanded our knowledge of the signaling pathways coordinatingmuscle protein turnover during various conditions including exercise. In this manuscript, the multiplemechanisms that govern the turnover of cellular components are reviewed, and their overall rolesin adaptations to exercise training are discussed. Recent studies have highlighted the central role ofthe energy sensor (AMP)-activated protein kinase (AMPK), forkhead box class O subfamily protein(FOXO) transcription factors and the kinase mechanistic (or mammalian) target of rapamycin complex(MTOR) in the regulation of autophagy for organelle maintenance during exercise. A new cellulartrafficking involving the lysosome was also revealed for full activation of MTOR and protein synthesisduring recovery. Other emerging candidates have been found to be relevant in organelle turnover,especially Parkin and the mitochondrial E3 ubiquitin protein ligase (Mul1) pathways for mitochondrialturnover, and the glycerolipids diacylglycerol (DAG) for protein translation and FOXO regulation.Recent experiments with autophagy and mitophagy flux assessment have also provided importantinsights concerning mitochondrial turnover during ageing and chronic exercise. However, data inhumans are often controversial and further investigations are needed to clarify the involvement ofautophagy in exercise performed with additional stresses, such as hypoxia, and to understand theinfluence of exercise modality. Improving our knowledge of these pathways should help developtherapeutic ways to counteract muscle disorders in pathological conditions

Autophagy, a Highly Regulated Intracellular System Essential to Skeletal Muscle Homeostasis — Role in Disease, Exercise and Altitude Exposure

Autophagy is an evolutionarily conserved intracellular system that selectively eliminates protein aggregates, damaged organelles, and other cellular debris. It is a self-cleaning process critical for cell homeostasis in conditions of energy stress. Autophagy has been until now relatively overlooked in skeletal muscle, but recent data highlight its vital role in this tissue in response to several stress conditions. The most recognized sensors for autophagy modulation are the adenosine monophosphate (AMP)-activated protein kinase (AMPK) and the mechanistic target of rapamycin (MTOR). AMPK acts as a sensor of cellular energy status by regulating several intracellular systems including glucose and lipid metabolisms and mitochondrial biogenesis. Recently, AMPK has been involved in the control of protein synthesis by decreasing MTOR activity and in the control of protein breakdown programs. Concerning proteolysis, AMPK notably regulates autophagy through FoxO transcription factors and Ulk1 complex. In this chapter, we describe the functioning of the different autophagy pathways (macroautophagy, microautophagy, and chaperone-mediated autophagy) in skeletal muscle and define the role of macroautophagy in response to physical exercise, a stress that is well assumed to be a key strategy to counteract metabolic and muscle diseases. The effects of dietary factors and altitude exposure are also discussed in the context of exercise

Influence of post-exercise hot-water therapy on long-term adaptations to training in elite short-track speed skaters

International audienceThis study aimed to investigate the effects of regular hot water bathing (HWB), undertaken 10 min after the last training session of the day, on chronic adaptations to training in elite athletes. Six short-track (ST) speed skaters completed four weeks of post-training HWB and four weeks of post-training passive recovery (PR) according to a randomized cross-over study. During HWB, participants sat in a jacuzzi (40 °C; 20 min). According to linear mixed models, maximal isometric strength of knee extensor muscles was significantly increased for training with HWB (p 0.05), including aerobic peak power output, the decline rate of jump height during 1 min-continuous maximal countermovement jumps (i.e. anaerobic capacity index), and the force-velocity relationship. Regarding specific tasks on ice, a small effect of training was found on both half-lap time and total time during a 1.5-lap all-out exercise (p = 0.0487; d = 0.23 and p = 0.0332; d = 0.21, respectively) but no additional effect of HWB was observed. In summary, the regular HWB protocol used in this study can induce additional effects on maximal isometric strength without compromising aerobic and anaerobic adaptations or field performance in these athletes

Pupil light reflex in young elite athletes: autonomic nervous system activity and viscoelastic properties

Introduction: The pupil light reflex (photomotor reflex) has a duration of 3.5 s and is a highly reproducible measurement. Conventionally, the autonomic nervous system (ANS) activity evaluated by this reflex does not consider the viscoelasticity of the iris muscles. This study aims to detect differences in reflex autonomic activity in a supine position with parameters derived from the Kelvin-Voigt viscoelastic model in two distinct groups of elite athletes.Method: Groups formed using a dendrogram analysis based on basal autonomic activity assessed with heart rate variability. Heart rate variability was measured, and the photomotor reflex was modeled.Results: The model showed a high degree of adjustment to the photomotor reflex (r2 = 0.99 ± 0.01). The impulse 3, an indicator of reflex sympathetic activity, revealed a significantly higher activity (ρ ≤ 0.05) in the [sympa/para]+ group compared to the [sympa/para]⁻ group. This result was further supported by a greater relative total redilation amplitude (ρ ≤ 0.05) and a shorter duration of 75% redilation (ρ ≤ 0.01). Finally, the relative total redilation amplitude exhibited a significant correlation with the linear stiffness constant (ρ ≤ 0.001) and the maximum redilation speed with restoring force (ρ ≤ 0.001).Discussion: These results indicate that (i) the photomotor reflex can detect an alteration of the reflex autonomic activity specific to each of the two branches of the ANS (ii) the viscoelastic properties of the iris muscles play a significant role in the energy storage-restitution mechanisms during the photomotor reflex. This approach could allow athletes to benefit from reduced time spent in the analysis of ANS activity, potentially making it an almost daily and automated process

A pragmatic approach to resolving technological unfairness: The case of Nike’s Vaporfly & Alphafly running footwear

Background Technology is often introduced into sport to facilitate it or to improve human performance within it. On occasion, some forms of novel technology require regulation or prevention entirely to ensure that a sport remains fair and accessible. Recently, the Nike Vaporfly and Alphafly shoes have received some concerns over their appropriateness for use in competitive distance running. Methods This paper evaluates the use of these shoes against an existing framework for sports technology discourse and adopts a pragmatic approach to attempt to resolve them. Results It is proposed that the three concerns regarding cost, access and coercion cannot be ruled out but likely remain short term issues. As a result, it is proposed that these running shoes are acceptable forms of technology but that ongoing vigilance will be required as such technologies develop further in the future. Conclusions The Nike Vaporfly/Alphafly shoes do push the perceived acceptability of running shoes to the limits of the current sports regulations. However, the alleged gains have not manifested themselves to a level that could be considered excessive when reviewing historical performances or when evaluated against a set of well-cited criteria. The sport will need to adopt a stance of ongoing vigilance as such technologies continue to develop or be optimised in the future

Les Equations de la marche

La marche peut être un exercice délicat, mais demeure un atout pour l'homme. Ce mode de déplacement peut varier en fonction de notre âge, de l'environnement dans lequel on se trouve et de la température. L'auteur explique quelles lois physiques sont impliquées dans cette manière de se déplacer. Un parallèle est établi avec la marche du gibbon

Stratégies d’épargne d'énergie de l’unité contractile

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