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ALTITUDE AND FOOTBALL: WHAT ARE NEW METHODS AND OPPORTUNITIES TO MAXIMIZE PLAYERS' FITNESS?

International audiencePlaying football competition at terrestrial altitude is not an isolated phenomenon. For instance, eight of the last 19 football FIFA World Cup tournaments were hosted by countries located at low-to-moderate altitude. While football-required fitness and technical qualities are affected by the development of neuromuscular fatigue at sea level, hypoxia-induced decrease in convective oxygen transport further hinders the aerobic capacity but also the ability to perform consecutive sprints, eventually impacting the outcome of a game. This results from the decrease in partial pressure of oxygen which reduces maximal aerobic power. The later, in turn, increases the relative intensity of any given absolute level of work, potentially delaying recovery of high-energy phosphates between high-intensity intermittent efforts. Despite reduction in air resistance (caused by the decrease in air density) could facilitate high-velocity running, it can also alter drag and lift, thereby impairing sensorimotor skills. Conversely, altitude/hypoxic training could help footballers preparing for competition at altitude, but also at sea level. Traditional altitude training camps involve chronic exposure to low-to-moderate terrestrial or simulated altitudes (14%) for improving oxygen-carrying capacity. While "live high-train high" or "live high-train low" paradigms are actually implemented by many elite club or national team football squads, the benefits they may have on (repeated-) sprint performance are still debated. The development of hypoxic technologies has led to the emergence of "live low-train high" methods, in isolation (i.e., the "repeated-sprint training in hypoxia" and "resistance training in hypoxia") or in combination with hypoxic/altitude residence (i.e., "live high-train low and high"). Today, the panorama of altitude/hypoxic training methods is wider than ever and includes also practices such as "blood flow restriction" or "ischemic preconditioning", which demonstrate encouraging preliminary results. The aims of this chapter are twofold: First, to summarize the effects of acute altitude/hypoxia exposure on football-specific qualities measured in the laboratory and/or during games at terrestrial altitude. Second, to discuss the potential benefits of each altitude/hypoxic training method in respect to sport-specific physiological and fitness development and/or in-game performance

Neurophysiological Mechanisms of Fatigue Résistance during Repeated Sprints in Hot and Hypoxic Environments: Application to Team Sports

In team sports, characterising fatigue is complex, with the underlying processes (e.g., metabolic energy supply, intramuscular accumulation of metabolic by-products, hyperthermia, dehydration) developing as match proceeds to ultimately manifest as a decline in physical performance. Using acute and chronic manipulations of environmental stress (i.e., heat or hypoxia) and unique tools (i.e., instrumented sprint treadmill, 45-m long hypoxic marquee), the main intention of this work was to better understand the neurophysiological and biomechanical manifestations of fatigue during repeated-sprint exercise. Our work first demonstrated the effect of heat stress on football matches outcomes. Next, we demonstrated during repeated treadmill sprints that (i) hot and hypoxic stresses do not accentuate the extent of fatigue-induced changes in running mechanics, (ii) alterations in RSA and associated neuro-mechanical responses with increase in hypoxia severity do not follow a monotonic (i.e., linear) pattern, and (iii) the rate of force development is not modified by hypoxia exposure. Lastly, we verified the putative benefit of the ‘repeated sprint training in hypoxia’ in a team- sport context and established the usefulness of the combination with ‘traditional’ hypoxic method, namely ‘live high-train low and high’, for inducing concomitant ‘aerobic’ and ‘anaerobic’ adaptive mechanisms via blood oxygen carrying-capacity improvement (i.e., haemoglobin mass gains) and muscle molecular up-regulations (i.e., hypoxia inducible factor- 1α subunit pathway and its target genes). In summary, our work provides deeper insights in the understanding of the neurophysiological mechanisms of fatigue resistance during repeated sprinting in the face of challenging environmental conditions and opens new frontiers in performance optimisation. -- En sports collectifs, la fatigue est un phénomène complexe, dont les processus sous-jacents (fourniture énergétique, accumulation de métabolites, hyperthermie, déshydratation) se développant au cours d’un match se manifestent par une baisse de performance physique. En manipulant le stress environnemental (chaleur ou hypoxie) de façon aigue ou chronique, à l’aide d’outils uniques (tapis de course instrumentée, tunnel hypoxique de 45 m de long), le but de ce travail est de mieux comprendre les manifestations neurophysiologiques et biomécaniques de la fatigue au cours de répétition de sprints. Notre travail a d’abord démontré l’effet de la chaleur sur les résultats de matchs de football. Ensuite, nous avons constaté qu’au cours de sprints répétés (i) l’ampleur des altérations mécaniques de la course ne diffère pas en condition chaude ou hypoxique, (ii) la baisse de performance et les réponses biomécaniques et neurophysiologiques associées à une augmentation du stress hypoxique ne suivent pas un pattern linéaire, et (iii) la capacité à développer la force rapidement n’est pas modifiée par la sévérité du stress hypoxique. Finalement, après avoir vérifié l'avantage de « l’entraînement de sprints répétés en hypoxie » dans les sports collectifs, nous avons développé et validé une nouvelle méthode d’entraînement – « vivre en altitude-s’entrainer au niveau de la mer et en altitude » – pour induire des gains aérobie et anaérobie concomitants via l’amélioration du transport d’oxygène dans le sang (augmentation de la masse en hémoglobine) et des adaptations moléculaires au niveau musculaire (activation du facteur inductible par hipoxie-1α et ses gènes cibles). En conclusion, notre travail a permis d’approfondir les connaissances des mécanismes neurophysiologiques de la résistance à la fatigue au cours de sprint répétés en référence à un stress environnemental et ouvre de nouvelles perspectives dans l’optimisation de la performance physique

Does ischemic pre-conditioning during the recovery period between two successive matches preserve physical performance in badminton doubles players?

Changes in physical performance were assessed in response to two successive doubles badminton matches with implementation of ischemic pre-conditioning (IPC) or sham treatment during recovery period between matches. Eight French national team badminton players (4 males, 4 females) performed two successive doubles matches (2 × 45 min), with 60 min of recovery in-between, during which they received three 5-min cycles of either an IPC (220 mmHg) or a sham (SHAM) (50 mmHg) intervention. A series of physical tests was performed immediately following the first (Post 1) and second (Post 2) match. Jump height (squat and countermovement jumps), leg power (multi-rebound jumps) and sprint time (L-test) remained unchanged from Post 1 to Post 2 (all P>0.193), and did not differ between conditions (all P>0.173). During a badminton-specific repeated-agility test, neither performance-related variables (i.e., best time, total time and sprint decrement score) nor vastus lateralis muscle tissue saturation index displayed a main effect for condition (all P>0.116), time (all P>0.091) or time × condition interaction (all P>0.730). Implementing IPC during the recovery period between successive doubles badminton demonstrated no beneficial effect on physical performance and muscle oxygenation trends

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Article de blogInternational audienc

La capacité à réitérer des sprints : une signature spécifique ?

La capacité à réitérer des sprints (ou « repeated sprint ability » [RSA] en anglais) consiste en des efforts maximaux (< 10 s) entrecoupés de périodes de récupération incomplète

Neuro-mechanical and metabolic adjustments to the repeated anaerobic sprint test in professional football players

Purpose: This study aimed to determine the neuro-mechanical and metabolic adjustments in the lower limbs induced by the running anaerobic sprint test (the so-called RAST). Methods: Eight professional football players performed 6×35m sprints interspersed with 10s of active recovery on artificial turf with their football shoes. Sprinting mechanics (plantar pressure insoles), root mean square activity of the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) muscles (surface electromyography, EMG) and VL muscle oxygenation (near-infrared spectroscopy) were monitored continuously. Results: Sprint time, contact time and total stride duration increased from the first to the last repetition (+17.4, +20.0 and +16.6%; all P0.05), decreased over sprint repetitions and were correlated with the increase in running time (r=−0.82 and −0.90; both P<0.05). Together with a better maintenance of RF and BF muscles activation levels over sprint repetitions, players with a better repeated-sprint performance (lower cumulated times) also displayed faster muscle de- (during sprints) and re-oxygenation (during recovery) rates (r=−0.74 and −0.84; P<0.05 and 0.01, respectively). Conclusion: The repeated anaerobic sprint test leads to substantial alterations in stride mechanics and leg-spring behaviour. Our results also strengthen the link between repeated-sprint ability and the change in neuromuscular activation as well as in muscle de- and re-oxygenation rates

Editorial: Sex differences in sport performance.

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