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Sprint performance can be characterized through the centre of mass (COM) velocity over time. In-field computation of the COM is key in sprint training.To compare the stance-averaged COM velocity computation from a Magneto-Inertial Measurement Units (MIMU) to a reference system: force platforms (FP), over the early acceleration phase in both straight and curve sprinting.Nineteen experienced-to-elite track sprinters performed 1 maximal sprint on both the straight and the curve (radius = 41.58 m) in a randomized order. Utilizing a MIMU-based system (Xsens MVN Link) and compared to FP (Kistler), COM velocity was computed with both systems. Averaged stance-by-stance COM velocity over straight-line and curve sprinting following the vertical axis (respectively V148 stances were analyzed. V

Resume Contexte Les lesions musculaires des ischio-jambiers sont frequentes dans les sports impliquant de la course a grande vitesse et peuvent avoir diverses consequences. Des programmes de prevention ont ete elabores pour reduire le risque de survenue de ces blessures, mais dans la pratique, et en dehors du contexte experimental, leur efficacite semble encore insuffisante et l’incidence de ces blessures reste importante. Il est a present admis que ces blessures sont d’origine multifactorielle, bien que de nombreuses etudes se soient interessees aux facteurs biomecaniques et physiologiques, les facteurs psychologiques et environnementaux ont ete peu traites jusqu’a present dans le cadre de cette blessure specifique. Objectif Recueillir les sensations, les emotions, les pensees et les intentions de sportifs ayant subi une lesion musculaire des ischio-jambiers durant la seance et, plus particulierement, les minutes precedant la survenue de la blessure. Methode Nous avons donc realise une etude qualitative par entretiens individuels semi-diriges, realises aupres de sportifs de la region stephanoise. Les participants ont ete recrutes d’avril a septembre 2020. Les informations ont ete recueillies jusqu’a suffisance des donnees retranscrites integralement, et une analyse thematique a ete realisee a partir des entretiens. Resultats Huit sportifs ont participe a cette etude. Deux principales notions ressortaient des entretiens : (1) celle de « depassement des limites » : le sportif s’est blesse en cherchant a atteindre le maximum de ce qu’il pouvait faire, et (2) celle d’un certain « deni de la douleur » avec un evitement des perceptions des signaux douloureux qui precedent le developpement de la blessure. Conclusions L’identification de deux schemas cognitifs (intention de se depasser et evitement des perceptions douloureuses) precedant la survenue d’une lesion des ischio-jambiers permet de mieux apprehender certains facteurs psychologiques de la survenue des blessures. Les resultats de cette etude offrent de nouvelles perspectives de prevention des blessures des ischio-jambiers.

ObjectivesTo identify individual characteristics associated with the adoption of injury risk reduction programmes (IRRP) and to investigate the variations in sociocognitive determinants (ie, attitudes, subjective norms, perceived behavioural control and intentions) of IRRP adoption in athletics (track and field) athletes.MethodsWe conducted a cross-sectional study using an online survey sent to athletes licensed with the French Federation of Athletics to investigate their habits and sociocognitive determinants of IRRP adoption. Sociodemographic characteristics, sports practice and history of previous injuries were also recorded. Logistic regression analyses and group comparisons were performed.ResultsThe final sample was composed of 7715 athletes. From the multivariable analysis, competing at the highest level was positively associated with IRRP adoption (adjusted OR (AOR)=1.66; 99.9% CI 1.39 to 1.99 and AOR=1.48; 99.9% CI 1.22 to 1.80) and presenting a low number of past injuries was negatively associated with IRRP adoption (AOR=0.48; 99.9% CI 0.35 to 0.65 and AOR=0.61; 99.9% CI 0.44 to 0.84), both during their lifetime and the current season, respectively. These results were supported by higher scores of sociocognitive determinants among athletes who reported IRRP adoption compared with other athletes.ConclusionSome characteristics of athletes seem to be associated with IRRP adoption either positively (competing at the highest level) or negatively (presenting a lower number of past injuries), whereas all the sociocognitive determinants tested appear to be linked to IRRP adoption. Since many athlete characteristics are difficult or impossible to change, IRRP promotion may be enhanced by targeting athletes’ beliefs and intentions to adopt an IRRP.

Purpose: The aim of this study was to investigate the time course of maximal isometric finger flexor force and blood acid–base balance during repeated simulated matches in world-class judokas. Methods: Seven 21- to 28-year-old world-class female judokas (including Olympic and World Championship medalists) repeated four 4-minute judo combats interspersed by 15 minutes of passive recovery. Maximal voluntary isometric finger flexor contraction (MVIC) force was measured in both hands after warm-up and immediately after each combat using a handgrip dynamometer. MVIC force was classified as MVIC hikite force (pulling hand) and MVIC tsurite force (lifting hand). Results: Blood lactate concentration, pH, bicarbonate concentration, partial pressure of oxygen, and oxygen saturation were measured between 3 and 5 minutes after each match. At completion of the fourth combat, mean MVIC hikite and tsurite force decreased by 18% and 12%, respectively (g = 0.23 and 0.29, respectively; P −1 after warm-up to 13.10 (2.61) mmol·L−1 after the last match (g = 4.13, P = .018). Concurrently, blood pH decreased slightly from 7.44 (0.03) to 7.26 (0.05) (g = 2.34, P = .018), that is, by only 0.18 units. The decreased blood pH was significantly correlated with a decrease in bicarbonate concentration (R2 = .94, P Conclusions: Female world-class judokas were able to maintain a high level of grip strength in both hands and efficiently regulate blood acid–base balance during repeated simulated high-intensity matches.

Thomas, C, Delfour-Peyrethon, R, Dorel, S, and Hanon, C. Positive effects of pre-exercise metabolic alkalosis on perceived exertion and post-exercise squat jump performance in world-class cyclists. J Strength Cond Res 36(9): 2602-2609, 2022-This study aimed to determine the effects of pre-exercise alkalosis in world-class cyclists on their general (rate of perceived exertion [RPE]) and local (category-ratio scale [CR10]) perceived rates of exertion and acid-base status during 2 types of training sessions. Eight world-class cyclists ingested either sodium bicarbonate (BIC) or a placebo (PLA) in a double-blind and randomized order before performing 4 × 1,000 m constant-power sprints (CP) or 3 × 500 m all-out sprints (AO), with 20 minutes of recovery time between each session. For AO, the performance was assessed through the cycling sprint velocity and a squat jump test during recovery. During both tests, RPE, CR10, and acid-base status were measured. Sodium bicarbonate ingestion was effective in inducing pre-exercise alkalosis, compared with a PLA ( p0.05). During CP, performance and RPE were the same for BIC and PLA ( p0.05) with no time effect. The CR10 increased for the last sprint in PLA ( p0.05) but was attenuated in BIC (BIC: 6 vs. PLA: 8.2; p0.05), whereas there was no difference in acid-base status. During AO, RPE and CR10 increased with time, with no BIC effect, whereas blood lactate concentration was different ( p0.05). Sodium bicarbonate supplementation had no effect on overall repeated sprints ( p0.05). However, world-class athletes responded to BIC with higher squat jump performance than the PLA condition after AO ( p0.05). Our results suggest a positive influence of pre-exercise alkalosis in world-class cyclists on local perception of efforts after constant load sprints and an attenuation of muscle power output decline postsprint, as evidenced by improved squat jump performance after all-out cycling effort.

International audience; Objective: To analyse the rates of lower limb muscle injuries in athletics disciplines requiring different running velocities during international athletics championships.Design: Prospective total population study.Methods: During 13 international athletics championships (2009–2019) national medical teams and local organizing committee physicians daily reported all newly incurred injuries using the same study design, injury definition and data collection procedures. In-competition lower limb muscle injuries of athletes participating in disciplines involving running (i.e. sprints, hurdles, jumps, combined events, middle distances, long distances, and marathon) were analysed.Results: Among the 12,233 registered athletes, 344 in-competition lower limb muscle injuries were reported (36% of all in-competition injuries). The proportion, incidence rates and injury burden of lower limb muscles injuries differed between disciplines for female and male athletes. The most frequently injured muscle group was hamstring in sprints, hurdles, jumps, combined events and male middle distances runners (43–75%), and posterior lower leg in female middle distances, male long distances, and female marathon runners (44–60%). Hamstring muscles injuries led to the highest burden in all disciplines, except for female middle distance and marathon and male long distance runners. Hamstring muscles injury burden was generally higher in disciplines requiring higher running velocities, and posterior lower leg muscle injuries higher in disciplines requiring lower running velocities.Conclusions: The present study shows discipline-specific injury location in competition context. Our findings suggest that the running velocity could be one of the factors that play a role in the occurrence/location of muscle injuries.

Resume Introduction Mieux comprendre les consequences psychologiques d’une blessure et l’influence de celle-ci sur les modifications de comportement et la realisation d’un programme de prevention semble pertinent pour la prise en charge therapeutique et dans une optique de prevention. Ainsi, l’objectif de cette presente etude a donc ete (1) d’analyser la perception des blessures par les athletes, et (2) d’analyser l’influence de celles-ci sur la realisation de mesures de prevention. Methodes Nous avons conduit une etude observationnelle quantitative retrospective nationale de recueil du ressenti des athletes de competition licencies a la Federation francaise d’athletisme vis-a-vis de leurs antecedents de blessures, leur perception de la blessure et les programmes de prevention des blessures, par un questionnaire informatique envoye aux athletes au printemps 2020. Resultats Au total, 7712 reponses d’athletes ont ete incluses dans cette analyse, incluant 37 % de femmes et 63 % d’hommes, âges de 37,9 ± 14,8 ans (de 18 a 87 ans), allant de niveau international a departemental, couvrant toutes les disciplines de l’athletisme. Soixante-dix pour cent des athletes n’avaient jamais realise de programme de prevention des blessures durant leur carriere, alors que 30 % estimaient en avoir suivi un de maniere partielle ou totale. Quatre-vingt dix pour cent des athletes avaient eu au moins une blessure depuis le debut de leur pratique. Les sportifs rapportaient qu’une blessure engendrait une tristesse, une frustration, un degout et une preoccupation de se refaire mal au meme endroit. Ils etaient conscients qu’une mauvaise prise en charge pouvait entrainer une recidive ou une nouvelle blessure. Les athletes avec antecedent de blessure realisaient significativement plus un programme de prevention des lesions que ceux ne s’etant jamais blesses. Ceux s’etant deja blesses croyaient en l’efficacite des programmes de prevention, davantage que ceux sans antecedent de blessure. En revanche, il n’y avait pas de difference de perception de l’interet de mesures preventives telles que l’hygiene de vie, l’ecoute de son corps, de ses douleurs et de sa fatigue entre les athletes avec et sans antecedent de blessures. Conclusion Une blessure peut entrainer des consequences psychologiques non negligeables pour l’athlete. Ses repercussions sont importantes a prendre en compte dans la prise en charge globale des lesions.

Couderc, A, Gabbett, TJ, Piscione, J, Robineau, J, Peeters, A, Igarza, G, Thomas, C, Hanon, C, and Lacome, M. Repeated high-intensity effort activity in international male Rugby Sevens. J Strength Cond Res XX(X): 000-000, 2018-Rugby Sevens is characterized by repeated high-intensity accelerations, sprinting, and collisions, commonly referred to as repeated high-intensity effort (RHIE) activity. Although repeated acceleration and sprinting activity of Rugby Sevens has been investigated, to date, no study has investigated the repeated running and collision activity of international Rugby Sevens during competitive events. In this study, 15 elite players competed in 44 matches during the HSBC World Sevens Series. Global positioning systems and match analysis software were used to quantify the frequency of repeated running and collision efforts. High acceleration (≥2.5 m·s), high speed (above maximal aerobic speed), sprint (above 85% of maximal sprint speed), and collision efforts (tackles, ruck, and contact) were considered as high-intensity effort activities. An RHIE bout was defined as 3 or more high-intensity efforts with less than 21 seconds recovery between efforts. The difference between positional groups (forward and backs) and first and second halves was compared using magnitude-based inferential statistics. One hundred twelve individual match observations were analyzed. On average, players performed 27 high-intensity effort events across the game. The distribution of high-intensity efforts included the following: 37% collisions, 34% accelerations, 27.5% high-velocity running, and 1.5% sprints. An average of 3.7 RHIE bouts was performed per player. The difference in high-intensity efforts and number of RHIE bouts performed were trivial/small when compared between first and second halves, and between forward and back positional groups. Repeated high-intensity effort bouts play an important role in the activity profile of elite Rugby Sevens players. This study could provide a framework for performance analysts and coaches to analyze match-related performance of elite Rugby Sevens players, taking into account both the high-intensity running and collision components of the game. Coaches should implement training interventions to ensure the maintenance of RHIE performance during competitive events.

Purpose This study determined the effects of pre-exercise sodium bicarbonate ingestion (ALK) on changes in oxygen uptake (V˙ O2) at the end of a supramaximal exercise test (SXT). Methods Eleven well-trained cyclists completed a 70-s all-out cycling effort, in double-blind trials, after oral ingestion of either 0.3 g kg−1 of sodium bicarbonate (NaHCO3) or 0.2 g kg−1 body mass of calcium carbonate (PLA). Blood samples were taken to assess changes in acid–base balance before the start of the supramaximal exercise, and 0, 5 and 8 min after the exercise; ventilatory parameters were also measured at rest and during the SXT. Results At the end of the PLA trial, which induced mild acidosis (blood pH = 7.20), subjects presented a significant decrease in V˙ O2 (P < 0.05), which was related to the amplitude of the decrease in minute ventilation (˙VE) during the SXT (r = 0.70, P < 0.01, n = 11). Pre-exercise metabolic alkalosis significantly prevented the exercise-induced decrease in V˙ O2 in eleven well-trained participants (PLA: 12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P < 0.05) and the decrease in mean power output was significantly less pronounced in ALK (P < 0.05). Changes in the V˙ O2 decrease between PLA and ALK trials were positively related to changes in the ˙VE decrease (r = 0.74, P < 0.001), but not to changes in power output (P > 0.05). Conclusions Pre-exercise alkalosis counteracted the V˙ O2 decrease related to mild acidosis, potentially as a result of changes in ˙V E and in muscle acid–base status during the all-out supramaximal exercise.

Purpose:To investigate the running demands and associated metabolic perturbations during an official rugby sevens tournament.Methods:Twelve elite players participated in 7 matches wearing GPS units. Maximal sprinting speed (MSS) and maximal aerobic speed (MAS) were measured. High-intensity threshold was individualized relative to MAS (>100% of MAS), and very-high-intensity distance was reported relative to both MAS and MSS. Blood samples were taken at rest and after each match.Results:Comparison of prematch and postmatch samples revealed significant (P < .01) changes in pH (7.41–7.25), bicarbonate concentration ([HCO3–]) (24.8–13.6 mmol/L), and lactate concentration ([La]) (2.4–11.9 mmol/L). Mean relative total distance covered was 91 ± 13 m/min with ~17 m/min at high-intensity. Player status (whole-match or interchanged players), match time, and total distance covered had no significant impact on metabolic indices. Relative distance covered at high intensity was negatively correlated with pH and [HCO3–] (r = .44 and r = .42, respectively; P < .01) and positively correlated with [La] (r = .36; P < .01). Total distance covered and distance covered at very high intensity during the 1-min peak activity in the last 3 min of play were correlated with [La] (r = .39 and r = .39, respectively; P < .01).Conclusions:Significant alterations in blood-metabolite indices from prematch to postmatch sampling suggest that players were required to tolerate a substantial level of acidosis related to metabolite accumulation. In addition, the ability to produce energy via the glycolytic energy pathway seems to be a major determinant in match-related running performance.

To investigate the effects of fatigue and metabolite accumulation on the postexercicse parasympathetic reactivation, 11 long-sprint runners performed on an outdoor track an exhaustive 400 m long sprint event and a 300 m with the same 400 m pacing strategy. Time constant of heart rate recovery (HRR), time (RMSSD), and frequency (HF, and LF) varying vagal-related heart rate variability indexes were assessed during the 7 min period immediately following exercise. Biochemical parameters (blood lactate, pH, PO2, PCO2, SaO2, and HCO3−) were measured at 1, 4 and 7 min after exercise. Time to perform 300 m was not significantly different between both running trials. HHR measured after the 400 m running exercise was longer compared to 300 m running bouts ( versus s, ). Absolute power density in the LF and HF bands was also lower after 400 m compared to the 300 m trial (). No correlation was found between biochemical and cardiac recovery responses except for the PO2values which were significantly correlated with HF levels measured 4 min after both bouts. Thus, it appears that fatigue rather than metabolic stresses occurring during a supramaximal exercise could explain the delayed postexercise parasympathetic reactivation in longer sprint runs.

This study aimed to determine metabolic and respiratory adaptations during intense exercise and improvement of long-sprint performance following six sessions of long-sprint training. Nine subjects performed before and after training (1) a 300-m test, (2) an incremental exercise up to exhaustion to determine the velocity associated with maximal oxygen uptake (v-VO2max), (3) a 70-s constant exercise at intensity halfway between the v-VO2max and the velocity performed during the 300-m test, followed by a 60-min passive recovery to determine an individual blood lactate recovery curve fitted to the bi-exponential time function: $$ {\text{La}}\left( t \right) = {\text{La}}\left( 0 \right) + A_{ 1} ( 1- {\text{e}}^{{ - \gamma_{{ 1 } }}^{{t}}} ) +\; A_{ 2} ( 1- {\text{e}}^{{ - \gamma_{{ 2 }} }^{{t}}} ) $$ , and blood metabolic and gas exchange responses. The training program consisted of 3–6 repetitions of 150–250 m interspersed with rest periods with a duration ratio superior or equal to 1:10, 3 days a week, for 2 weeks. After sprint training, reduced metabolic disturbances, characterized by a lower peak expired ventilation and carbon dioxide output, in addition to a reduced peak lactate (P

Objectifs: Cette etude a pour objectif d’explorer l’interet des relations inertielles charge–vitesse et charge–puissance dans l’identification des zones d’entrainement musculaire. Methodes: Trente-cinq sujets sont venus a deux reprises au laboratoire. La premiere seance a permis de definir la repetition maximale (1RM) en developpe couche alors que la seconde a permis de definir les profils musculaires charge–vitesse et charge–puissance a partir d’un dynamometre inertiel. Quatre zones d’entrainement (vitesse maximale, puissance–vitesse, puissance–force et force maximale) habituellement definies a partir du 1RM ont ete comparees aux zones d’entrainement objectivees pour chaque individu a partir des relations charge–vitesse et charge–puissance. Resultats: Les zones d’entrainement obtenues lorsque l’on se base sur les relations charge–vitesse et charge–puissance different significativement (p < 0,001) de celles etablies sur base du seul 1RM. Les resultats montrent que de 0 a 23 % du 1RM, on travaille la vitesse ; de 25 a 54 % du 1RM, on travaille la puissance–vitesse ; de 54 a 82 % du 1RM, on travaille la puissance-force et au-dela, on travaille la force maximale. Des differences interindividuelles ont ete constatees. L’etablissement de ces profils inertiels permet une definition precise et individualisee de l’entrainement de la vitesse et de la puissance musculaire.

The purpose of this study was to determine whether exhaustion modifies the stiffness characteristics, as defined in the spring-mass model, during track running. We also investigated whether stiffer runners are also the most economical. Nine well-trained runners performed an exhaustive exercise over 2000 meters on an indoor track. This exhaustive exercise was preceded by a warm-up and was followed by an active recovery. Throughout all the exercises, the energy cost of running (Cr) was measured. Vertical and leg stiffness was measured with a force plate (Kvert and Kleg, respectively) integrated into the track. The results show that Cr increases significantly after the 2000-meter run (0.192 +/- 0.006 to 0.217 +/- 0.013 mL[middle dot]kg-1[middle dot]m-1). However, Kvert and Kleg remained constant (32.52 +/- 6.42 to 32.59 +/- 5.48 and 11.12 +/- 2.76 to 11.14 +/- 2.48 kN[middle dot]m-1, respectively). An inverse correlation was observed between Cr and Kleg, but only during the 2000-meter exercise (r = -0.67; P

International audience; This study aimed to compare the response of salivary hormones of track and field athletes induced by preparation and pre-competitive training periods in an attempt to comment on the physiological effects consistent with the responses of each of the proteins measured. Salivary testosterone, cortisol, alpha-amylase, immunoglobulin A (IgA), chromogranin A, blood creatine kinase activity, and profile of mood state were assessed at rest in 24 world-class level athletes during preparation (3 times in 3 months) and pre-competitive (5 times in 5 weeks) training periods. Total mood disturbance and fatigue perception were reduced, while IgA (+61%) and creatine kinase activity (+43%) increased, and chromogranin A decreased (−27%) during pre-competitive compared to preparation period. A significant increase in salivary testosterone (+9 to +15%) and a decrease in testosterone/cortisol ratio were associated with a progressive reduction in training load during pre-competitive period (P < 0.05). None of the psycho-physiological parameters were significantly correlated to training load during the pre-competitive period. Results showed a lower adrenocortical response and autonomic activity, and an improvement of immunity status, in response to the reduction in training load and fatigue, without significant correlations of salivary hormones with training load. Our findings suggest that saliva composition is sensitive to training contents (season period) but could not be related to workload resulting from track and field athletics training.

This study determined the effects of pre-exercise sodium bicarbonate ingestion (ALK) on changes in oxygen uptake (VO2) at the end of a supramaximal exercise test (SXT).Eleven well-trained cyclists completed a 70-s all-out cycling effort, in double-blind trials, after oral ingestion of either 0.3 g kg(-1) of sodium bicarbonate (NaHCO3) or 0.2 g kg(-1) body mass of calcium carbonate (PLA). Blood samples were taken to assess changes in acid-base balance before the start of the supramaximal exercise, and 0, 5 and 8 min after the exercise; ventilatory parameters were also measured at rest and during the SXT.At the end of the PLA trial, which induced mild acidosis (blood pH = 7.20), subjects presented a significant decrease in VO2 (P0.05), which was related to the amplitude of the decrease in minute ventilation (VE) during the SXT (r = 0.70, P0.01, n = 11). Pre-exercise metabolic alkalosis significantly prevented the exercise-induced decrease in VO2 in eleven well-trained participants (PLA:12.5 ± 2.1 % and ALK: 4.9 ± 0.9 %, P0.05) and the decrease in mean power output was significantly less pronounced in ALK (P0.05). Changes in the VO2 decrease between PLA and ALK trials were positively related to changes in the VE decrease (r = 0.74, P0.001), but not to changes in power output (P0.05).Pre-exercise alkalosis counteracted the VO2 decrease related to mild acidosis, potentially as a result of changes in VE and in muscle acid-base status during the all-out supramaximal exercise.

International audience; Hanon, C, Savarino, J, and Thomas, C. Blood lactate and acid-base balance of world-class amateur boxers after three 3-minute rounds in international competition. J Strength Cond Res 29(4): 942–946, 2015—To examine the blood metabolic responses of world-class boxers involved in international competition (Test match), 33 male boxers (mean 6 SD) competing internationally across all the official weight categories were studied on 2 different occasions: Test match 1 (team A against team B) and Test match 2 (team A against team C). Blood samples were collected after the third round for both Test matches for all teams except team B. For all Test matches and boxers, mean blood lactate concentration ([BLac]), bicarbonate concentration, hemo-globin O 2 saturation (SaO 2), partial pressure for CO 2 (PCO 2), and pH were 13.6 6 2.4 mmol$L 21 , 13.2 6 2.3 mmol$L 21 , 95.0 6 2.6%, 32.0 6 5.5 mm Hg, and 7.22 6 0.06 with 7/20 final pH values ,7.20. The intermediate category (60–64 kg) was characterized by the greatest [BLac] (14.8 6 2.9) compared with the heaviest and lighter boxers (;12 mmol$L 21). During the second match (team A again team C), a significant difference between pH, PCO 2 , and SaO 2 values was observed with no concomitant difference in [BLac] suggesting a better buffering capacity in team A. This result highlights the need for a well-developed anaerobic and buffering capacity and indicates that world-class boxers must be able to tolerate a substantial level of acidosis to produce high levels of boxing activity until the end of a match.

International audience; This study analysed the changes in the elec-tromyographic activity (EMG) of the vastus lateralis muscle (VL) during an incremental maximal oxygen uptake test on a treadmill. A breakpoint in the integrated electromyogram (iEMG)-velocity relationship has already been interpreted in two ways: either as a sign of neuromuscular fatigue or as an expression of the iEMG-velocity relationship characteristics. The aim of this study was to test a method of distinguishing fatigue e€ects from those due to increases in exercise power. Eight well-trained male runners took part in the study. They completed a running protocol consisting of 4-min stages of increments in power output. Between each stage (about 15 s after the start of a minute at rest), the subjects had to maintain a standard e€ort: a 10-s iso-metric leg extension contraction [50% isometric maximal voluntary contraction (IMVC)]. The EMG was recorded during the running and isometric protocols, a change in the EMG signal during the isometric exercise being considered as the sign of fatigue. The iEMG-velocity relationships were strongly ®tted by a second-order polynomial function for data taken at both the start (r ˆ 0.98) and the end (r ˆ 0.98) of the stage. Based on the stability of the 50%IMVC-iEMG relationship noted between stages, the start-iEMG has been identi-®ed as expressing the iEMG-velocity relationship without fatigue. The stage after which end-iEMG increased signi®cantly more steeply than start-iEMG was considered as the iEMG threshold and was simultaneous with the ventilatory equivalent for carbon dioxide threshold. The parallel changes of minute ventilation and iEMG would suggest the existence of common regulation stimuli linked either to e€ort intensity and/or to metabolic conditions. The fall in intracellular [K + ] has been discussed as being one of the main factors in regulating ventilation.

To investigate the physiological mechanisms that explain the end-exercise decrease in oxygen uptake during strenuous constant-power exercise, we recruited eleven trained, track cyclists. On two separated days they performed 1) resting spirometric measures, followed by an incremental test on a cycle ergometer to determine the power output at and 2) an exhaustive isokinetic supramaximal cycling exercise (Tlimsupra) at 185 ± 24% of (i.e., 640.5 ± 50.8 W). During cycling exercise tests, , ventilation parameters, stroke volume (SV) and heart rate were continuously recorded. Furthermore, arterialised capillary blood samples were collected to measure blood pH, arterial oxygen saturation, lactate and bicarbonate concentration before and 5 min after Tlimsupra. A > 5% decrease in and/or SV was observed in 6 subjects, with 5 out of 6 subjects presenting both phenomena. The magnitude of the decrease was correlated with the magnitude of the SV decrease (R = 0.75, P

International audience; La boxe anglaise est un sport technique occasionnant une dépense énergétique importante (Dal Monte et Menchinelli, 1986 ; Victorov et al, 1976). L'entraîneur doit intégrer les deux composantes, technique et énergétique, dans la préparation des boxeurs. L'entraînement technique se fait lors de séances spécifiques de type « frappe au sac » ou combat. L'entraînement physique se fait soit sous forme de course à pied ou de « saut à la corde », soit lors de séances plus spécifiques comme la «frappe au sac». Ces séances d'entraînement font partie de la « culture pugilistique » et ont été peu modifiées ces dernières années. Aussi, pour définir la programmation de l'entraînement, est-il important de connaître la nature des sollicitations du métabolisme énergétique lors de ces séances. Or peu d'études dans le domaine de la boxe anglaise ont été réalisées. Ces études ont utilisé la fréquence cardiaque. Victorov et al (1976) ont utilisé la fréquence cardiaque pour évaluer quantitativement l'intensité des charges d'entraînement. Dal Monte et Menchinelli (1986) ont étudié l'évolution de la fréquence cardiaque au cours de combats amateurs de boxe anglaise. Leur conclusion est que les combats sollicitent alternativement les métabolismes aérobie et anaérobie. Le fait que ces études utilisent uniquement la fréquence cardiaque ne permet pas de déterminer avec précision la filière énergétique dominante pour chaque exercice. C'est pour cette raison que nous avons essayé de mettre en relation dans cette étude la lactatémie et la fréquence cardiaque mesurées sur le terrain et les mêmes paramètres mesurés en laboratoire pour étudier le métabolisme énergétique sollicité lors des séances d'entraînement chez des boxeurs de haut niveau.

The purpose of this study was to analyze 2 different long-sprint training programs (TPs) of equal total work load, completed either with short recovery (SR) or long recovery (LR) between sets and to compare the effects of 6 long-sprint training sessions (TSs) conducted over a 2-week period on a 300-m performance. Fourteen trained subjects performed 3 pretraining maximal sprints (50-, 100-, and 300-m), were paired according to their 300-m performance, and randomly allocated to an LR or SR group, which performed 6 TSs consisting of sets of 150, 200, or 250 m. The recovery in the LR group was double that of the SR group. During the third TS and the 300-m pretest and posttest, blood pH, bicarbonate concentration ([HCO₃⁻]), excess-base (EB), and lactate concentration were recorded. Compared with a similar TS performed with SR, the LR training tends to induce a greater alteration of the acid-base balance: pH: 7.09 ± 0.08 (LR) and 7.14 ± 0.05 (SR) (p = 0.10), [HCO₃⁻]: 7.8 ± 1.9 (LR) and 9.6 ± 2.7 (SR) (p = 0.04), and EB: -21.1 ± 3.8 (LR) and -17.7 ± 2.8 (SR) (p = 0.11). A significant improvement in the 300-m performance between pre-TP and post-TP (42.45 ± 2.64 vs. 41.52 ± 2.45, p = 0.01) and significant decreases in pH (p < 0.01), EB (p < 0.001) and increase in [La] (p < 0.001) have been observed post-TP compared with those pre-TP. Although sprint training with longer recovery induces higher metabolic disturbances, both sprint training regimens allow a similar 300-m performance improvement with no concomitant significant progress in the 50- and 100-m performance.

The aim of this study was to describe and compare the blood metabolic responses obtained after a single maximal exercise in elite and less-successful athletes and to investigate whether these responses are related to sprint performance. Eleven elite (ELI) and 14 regional (REG) long sprint runners performed a 300-m running test as fast as possible. Blood samples were taken at rest and at 4 minutes after exercise for measurements of blood lactate concentration [La] and acid-base status. The blood metabolic responses of ELI subjects compared to those of REG subjects for pH (7.07 ± 0.05 vs. 7.14 ± 1.5), sodium bicarbonate concentration ([HCO(3)(-)], 8.1 ± 1.5 vs. 9.8 ± 1.8 mmol·L(-1)), hemoglobin O(2) saturation (SaO(2)) (94.7 ± 1.8 vs. 96.2 ± 1.6%) were significantly lower (p0.05), and [La] was significantly higher in ELI (21.1 ± 2.9 vs. 19.1 ± 1.2 mmol·L(-1), p0.05). The 300-m performance (in % world record) was negatively correlated with pH (r = -0.55, p0.01), SaO2 (r = -0.64, p0.001), [HCO(3)(-)] (r = -0.40, p0.05), and positively correlated with [La] (r = 0.44, p0.05). In conclusion, for the same quantity of work, the best athletes are able to strongly alter their blood acid-base balance compared to underperforming runners, with larger acidosis and lactate accumulation. To obtain the pH limits with acute maximal exercise, coaches must have their athletes perform a distance run with duration of exercise superior to 35 seconds. The blood lactate accumulation values (mmol·L(-1)·s(-1)) recorded in this study indicate that the maximal glycolysis rate obtained in the literature from short sprint distances is maintained, but not increased, until 35 seconds of exercise.

International audience; The aim of this study was to compare the evolution of oxygen uptake ( _V O2) in specifically trained runners during runningtests based on the 400-, 800-, and 1500-m pacing strategies adopted by elite runners to optimize performance. Final velocitydecreased significantly for all three distances, with the slowest velocity in the last 100 m expressed relative to the peakvelocity observed in the 400 m (77%), 800 m (88%), and 1500 m (96%). Relative to the previously determined _V O2maxvalues, the respective _V O2peak corresponded to 94% (400 m) and 100% (800 and 1500 m). In the last 100 m, a decreasein _V O2 was observed in all participants for the 400-m (15.6+6.5%) and 800-m races (9.9+6.3%), whereas a nonsystematicdecrease (3.6+7.6%) was noted for the 1500 m. The amplitude of this decrease was correlated with thereduction in tidal volume recorded during the last 100 m of each distance (r¼0.85, P50.0001) and with maximal bloodlactate concentrations after the three races (r¼0.55, P50.005). The present data demonstrate that the 800 m is similar tothe 400 m in terms of decreases in velocity and _V O2.

This study aimed to investigate the oxygen uptake and metabolic responses during a 400-m run reproducing the pacing strategy used in competition. A portable gas analyser was used to measure the oxygen uptake (V˙O2) of ten specifically trained runners racing on an outdoor track. The tests included (1) an incremental test to determine maximal V˙O2(V˙O2max) and the velocity associated with V˙O2max(v−V˙O2max), (2) a maximal 400-m (400T) and 3) a 300-m running test (300T) reproducing the exact pacing pattern of the 400T. Blood lactate, bicarbonate concentrations [HCO−3], pH and arterial oxygen saturation were analysed at rest and 1, 4, 7, 10 min after the end of the 400 and 300T. The peak V˙O2V˙O2 recorded during the 400T corresponded to 93.9 ± 3.9% of V˙O2maxV˙O2max and was reached at 24.4 ± 3.2 s (192 ± 22 m). A significant decrease in V˙O2 (P < 0.05) was observed in all subjects during the last 100 m, although the velocity did not decrease below v−V˙O2max. The V˙O2 in the last 5 s was correlated with the pH (r = 0.86, P < 0.0005) and [HCO−3] (r = 0.70, P < 0.05) measured at the end of 300T. Additionally, the velocity decrease observed in the last 100 m was inversely correlated with [HCO−3][HCO3−] and pH at 300T (r = −0.83, P < 0.001, r = −0.69, P < 0.05, respectively). These track running data demonstrate that acidosis at 300 m was related to both the V˙O2 response and the velocity decrease during the final 100 m of a 400-m run.

International audience; The purpose of this study was to determine, based on the time course of the velocity and stride pattern recorded in each 50-m segment of a 400-m competition, whether elite 400-m runners present the same pacing strategy as less successful athletes. Based on video data, 3 different levels of performance were analyzed: world-class, national, and regional levels for both sexes, with each of the 6 groups comprising 5 subjects. The peak velocity was reached by all athletes between the 50-and 100-m marks with mean values of 8.96 and 10.12 m.s-1 for the 5 best women and men, respectively. Peak frequencies were observed in the second and third 50-m segments; peak values were 3.99 6 0.13 for the world-class women (WWC) and 4.12 6 0.19 for the men (MWC). A stride length of 2.29 6 0.04 was observed for the WWC and 2.53 6 0.08 for the MWC. The better athletes were able to achieve higher absolute and relative velocities (97.6 6 0.5 [MWC] and 96.3 6 0.7% [WWC] of their best performance for 200 m) at the 200-m mark compared with the lower-level athletes. Furthermore, the fatigue index was calculated as 22.99, 14.43, and 13.91% for the world-class, national, and regional levels, respectively. In summary, world-class runners adopt a more aggressive pacing strategy and demonstrate greater fatigue than the less experienced runners; this might indicate a greater mental commitment and/or a better capacity to run under fatigue.

International audience; Purpose: We compared incline and level training sessions as usually used in elite 400-m runners through stride kinematics and muscular activity measurements. Methods: Nine highly trained 400-m ramiers (international and French national level) performed two maximal velocity sprints: 1) 300-m on level ground (LEV) and 2) 250-m on an incline ground (INC) characterized by a mean ± SD grade of 5.4 ± 0.7%. Kinematics (250 Hz) and electromyography parameters (root mean square [RMS] and integrated electromyography [iEMG] measurements) were analyzed (from 40-to 50-m phases). Results: INC induced a decrease in running velocity compared to LEV (6.28 ± 0.38 vs 7.56 ± 0.38 ms-1) explained by a reduction in stride length (-14.2%) and stride rate (-7.4%) and by an increase in push-off time (+26.4%). Kinematics analysis indicated that the lower limbs were more flexed during INC running. Concerning the level of activity of the lower limb muscles, the major findings pointed out the decrease in RMS for semitendinosus and biceps femoris muscles during the contact phase and for vastus lateralis during its concentric phase. However, iEMG of both semitendinosus and biceps femoris muscles remained constant during both contact and push-off phases. Conclusion: Our results are clearly different from those of previous studies carried out at similar absolute velocities in both LEV and INC conditions, which were not the case in this study. The lower running velocity marking INC running was associated with a decrease in the activation of the hamstrings. Trainers should particularly consider this lower level of activation of the hamstrings muscles during INC maximal sprint.

We investigated the oxygen uptake response (V.O (2)) to a 1500-m test conducted using a competition race strategy. On an outdoor track, eleven middle-distance runners performed a test to determine V.O (2max), velocity associated with V.O (2max) (v-V.O (2max)) and a supramaximal 1500-m running test (each test at least two days apart). V.O (2max) response was measured with the use of a miniaturised telemetric gas exchange system (Cosmed, K4, Roma, Italy). The 1500-m running test was performed at a mean velocity of 107. 6 + 2 % v-V.O (2max). The maximal value of oxygen uptake recorded during the 1500-m test (V.O (2peak)) was reached by subjects at 75.9 + 7.5 s (mean + SD) (i.e., 459 +/- 59 m). The time to reach V.O (2max) (TV.O (2peak)) and the start velocity (200- to 400-m after the onset of the 1500 m) expressed in % v-V.O (2max) were negatively and significantly correlated (p < 0.05), but our results indicate that a fast start does not necessarily induce a good performance. These results suggest that V.O (2max) is reached by all the subjects at the onset of a simulated 1500-m running event and are therefore in contrast with previous results obtained during treadmill running.

International audience; This study analyses the changes in the electro-myographic activity (EMG) of six major muscles of the leg during an incremental running test carried out on a treadmill. These muscles, the gluteus maximus (GM), biceps femoris (BF), vastus lateralis (VL), rectus femoris (RF), tibialis anterior (TA) and gastrocnemius (Ga) are known to have quite different functions during running. The aim of this study was to develop a methodology adapted to the analysis of integrated EMG (iEMG) running results, and to test the chronology of the onset of fatigue of the major muscles involved in running. Nine well-trained subjects [ _ V O 2max 76 (2.9) ml.min À1 .kg À1 ] took part in this study. They completed a running protocol consisting of 4 min stages, incrementally increasing in speed until exhaustion. The EMG signal was recorded during ten bursts of activation analysed separately at 45 s and 3 min 40 s of each stage. During running, consideration of the alteration in stride frequency with either an increase in speed or the onset of fatigue appears to be an indispensable part of the assessment of muscular fatigue. This allows the comparison of muscular activation between the various stage speeds by the use of common working units. Distance seems to be the only working unit that allows this comparison and thus the determination of the appearance of fatigue during running. The biarticular hip-mobilising muscles (RF and BF), which present two different bursts of activation during one running cycle, are the muscles that show the earliest signs of fatigue.

Muscular activity of the lower limbs during flat running The primary objective of this article is to describe the main muscle activity of the lower limbs during flat running. The examination of the literature on this subject emphasizes the fact that the mono-articular muscles are only once activated during the stride cycle (vastus lateralis, gluteus maximus). The bi-articular muscles are activated twice: whatever the speed for the biceps femoris and once or twice depending on the speed for the rectus femoris and the gastrocnemius. From this, certain muscles are activated strongly but briefly (gastrocnemius, vastus lateralis), while others are activated weakly but for a long time (tibialis anterior) and others still, such as the rectus femoris and the biceps femoris are activated long and strongly. Raising the speed has a significant impact on these data by increasing the levels of activation and by modifying more or less the activations patterns. The consequences of fatigue result in an increase in the ratio period of work / period of relaxation, as well as in an increase in the relationship EMGi / Force. Finally, the consequences of the level of expertise on patterns and levels of activity, although discussed only infrequently in the literature, are presented in relation to their role with regard to both the energetic cost and the evolution of these patterns with fatigue., Cet article a pour objectif principal de décrire l'activité des principaux muscles des membres inférieurs dans la course à pied sur le plat. L'examen de la littérature à ce sujet permet de mettre en avant le fait que les muscles mono-articulaires sont activés une seule fois au cours du cycle de la foulée (vastus lateralis, gluteus maximus). Les muscles bi-articulaires sont activés deux fois : quelle que soit la vitesse pour le biceps femoris et une ou deux fois selon la vitesse pour le rectus femoris et le gastrocnemius. De ce fait, certains muscles sont activés fortement mais brièvement (gastrocnemius, vastus lateralis), d'autres sont activés faiblement mais longtemps (tibialis anterior) et d'autres encore tels que le rectus femoris et le biceps femoris sont activés assez longuement et assez fortement. L'élévation de la vitesse influe très largement sur ces données en augmentant les niveaux d'activation et en modifiant peu ou prou les patterns d'activation. Les conséquences liées à la fatigue se traduisent par une augmentation du rapport temps de travail / temps de relaxation, et à une augmentation du rapport EMGi / force. Enfin, les conséquences du niveau d'expertise sur les patterns et niveaux d'activité, quoique peu abordées dans la littérature, sont présentées dans leur lien avec le coût énergétique et dans l'évolution de ces patterns avec la fatigue.

We tested the hypothesis that time course of O (2) uptake (VO (2)) measured during a supramaximal exercise performed in the field is driven to maximal oxygen uptake (VO (2max)). On an outdoor track, five middle-distance male runners first performed a test to determine VO (2max) and a supramaximal 800-m running test at least two days apart. VO (2) response was measured from the start to the end of exercise with the use of a miniaturised telemetric gas exchange system (Cosmed K4). VO (2max) was reached by all subjects 45 +/- 11 s (mean +/- SD) after the onset of the 800-m race (i.e., 316 +/- 75 m), and was maintained during the next 33 +/- 6 s (i.e., 219 +/- 41 m). The mean relative exercise intensity of the 800 m was 120 % VO (2max). An unexpected significant decrease in VO (2) (24.1 +/- 7.0 %; p0.05) was observed in all subjects during the final 38 +/- 17 s (i.e., the last 265 +/- 104 m). We concluded that, at onset of a simulated 800 m running event, VO (2) is quickly projected towards the VO (2max), and then becomes limited by the achievable VO (2max). This race profile shown by all athletes is in some contrast to what can be expected from earlier findings in a laboratory setting.

Gajer Bruno, Hanon Christine, Lehénaff Didier, Vollmer Jean-Claude. Analyse comparée de différentes séances de développement de VO2max. In: Les Cahiers de l'INSEP, n°34, 2003. Expertise et sport de haut niveau. pp. 43-47.

Vallier Jean-Marc, Hanon Christine, Gautier T., Brisswalter J., Savarino J. Aspects physiologiques de la boxe anglaise. In: Les Cahiers de l'INSEP, n°12-13, 1996. Arts martiaux, sports de combat. pp. 121-122.

Resume Objectif – Determiner la part de chaque systeme energetique aux differents moments d'un 800 m couru sur le mode de competition en mesurant en continu la consommation d'oxygene et la vitesse reelle de course. Materiels et methodes – Cinq athletes ont ainsi effectue sur une piste de 400 m, un test progressif de determination de la consommation d'oxygene maximale et de la vitesse maximale aerobie ainsi qu'un exercice supramaximal de 800 m. Resultats – Ils mettent en evidence une depense energetique globale et un deficit d'oxygene evalue a 31,9 % quasi-identiques a ceux obtenus au cours d'un 800 m realise sur tapis roulant mais montrent une repartition differente du deficit d'oxygene. Ceci suggere que la cinetique des vitesses a une incidence determinante aussi bien sur la contribution anaerobie qu'aerobie lorsque existent des variations de vitesse importantes.

Our thesis research fits within the framework of sport science. Based on the exploration of physical and physiological characteristics, technical and physical performance achieved by the French Rugby 7’s team, were studied through the analysis of international tournaments.In the first study, we observe the impact of contextual variables on the physical and technical performance of players during a Rugby 7’s game. The results demonstrate that the level of the opponent and the match result influence the activity of players. Players are likely to perform better physically during a game for which the outcome is favorable. They increase the total distance run in a game against a weaker opponent. For the first time in Rugby 7’s, we were able to show that technical performance is also affected whilst playing against a stronger opponent as there is a decrease in the number of passes and the number of situations where players are ball carriers.Through a physiological approach, the second study focuses on the individual metabolic responses of players during an international Rugby 7’s tournament. The results show a significant relationship between lactate concentrations and peaks activity recorded in the last three minutes of play, suggesting the ability to provide energy via the glycolytic pathway as a fundamental requirement in this sport. Also, the acid-base balance significantly changes towards the end of a game showing that Rugby 7’s players must be able to tolerate a high level of acidosis because the high amount of energy needed for games at an international level.Finally, our last study focuses on high intensity actions done during a Rugby 7’s game. The results show that a player does on average ~26 high intensity actions per game. In addition and for the first time in this sport, we show that approximately 4 sequences of repeated high intensity actions are recorded in a game, the average duration is 40 seconds and includes a time of recovery of under 9 seconds. Thus, Rugby 7’s may be considered as a team sport of repeated high intensity actions.To conclude, this thesis will allow Rugby 7’s coaches and fitness coaches, to better plan and prepare specific trainings that would be adapted to Rugby 7’s., Ce travail de thèse s’inscrit dans le cadre de travaux menés en sciences du sport. Basé sur l’exploration des caractéristiques physiques et physiologiques, les performances techniques et physiques des joueurs de l’équipe de France de Rugby à 7, ont été étudiées au travers de l’analyse de tournois internationaux.Dans une première étude, nous avons observé l’impact de variables contextuelles sur les performances physiques et techniques des joueurs en match. Les résultats démontrent que le niveau de l'adversaire ainsi que le résultat du match influencent l’activité des joueurs.Ces derniers sont susceptibles de réaliser de meilleures performances physiques au cours de match dont l’issue est favorable. En effet, les joueurs augmentent la distance totale parcourue dans un match contre un adversaire plus faible. Pour la première fois en Rugby à 7, nous avons montré que les performances techniques sont elles aussi influencées lorsque les joueurs de l’équipe de France jouaient contre une équipe plus forte. En effet, nous avons observé des diminutions du nombre de passes et de situations où les joueurs sont porteurs de balle.Au travers d’une approche physiologique, une deuxième étude a appréhendé les réponses métaboliques individuelles des joueurs de l’équipe de France durant un tournoi international. Les résultats ont montré des relations significatives entre les concentrations de lactate et les pics d’activité enregistrés dans les trois dernières minutes de jeu, ce qui suggère que la capacité à fournir de l'énergie via la voie de la glycolyse est une exigence fondamentale dans cette discipline. L'équilibre acido-basique modifié de façon significative en fin de match, indique que les joueurs doivent être capables de tolérer un niveau important d'acidose due à une forte sollicitation énergétique lors des matchs internationaux.Enfin, notre dernière étude s’est centrée sur les actions de haute intensité effectuées en match. Ces derniers résultats de recherche ont permis de démontrer qu’un joueur réalise en moyenne ~26 actions de haute intensité par match. De plus et pour la première fois dans cette discipline, nous avons montré qu’environ 4 séquences de répétitions d’actions de haute intensité sont comptabilisées en match, dont la durée moyenne est d’environ 40 secondes et comprennent des temps de récupérations inférieurs à 9 secondes. Ainsi, le Rugby à 7 peut être considéré comme un sport collectif de répétitions d’efforts intenses.Pour conclure alors, ces travaux de thèse vont permettre aux entraîneurs et préparateurs physiques de Rugby à 7, de pouvoir s’inspirer de nos résultats pour planifier et mettre en œuvre des entraînements spécifiques aux exigences du Rugby à 7.

This thesis falls within the general framework of the energetic physiology, and includes three studies, ranging from global exploration of the humans in motion (field tests with athletes of the French Cycling Team, laboratory exploration during exercise on trained cyclists) to studies of muscle metabolism by techniques of cellular and molecular investigations in active subjects. This work has focused on high-intensity exercise generating high levels of muscle fatigue and the resulting adaptive cardiorespiratory and muscular responses. Supplementation of sodium bicarbonate against placebo was used to study the precise role of the accumulation of protons during sprint cycling sessions. Through this work, we have shown that, if an induced alkalosis did not systematically improve sprint cycling performances, a significant disruption of the pH led to changes in oxygen transport during exercise, in mitochondrial function after 24h of recovery, but also in the expression of some proteins involved in pH regulation (i. E. , lactate/proton co-transporter (MCT1) its chaperone protein CD147, and the sodium/proton exchanger (NHE1)). These changes were related to a reduction of the oxidative stress induced by alkalosis, suggesting a harmful role of the carbonylation in these protein expressions. These results provide a new perspective on the role played by acidosis in the regulatory mechanisms at physiological, cellular and molecular levels in humans.; Ce travail de thèse s’inscrit dans le cadre général de la physiologie énergétique, et comprend trois études, qui vont de l’exploration globale de l’Homme en mouvement (tests de terrain chez des athlètes de l’Equipe de France de Cyclisme, explorations à l’effort en laboratoire chez des cyclistes entrainés) jusqu’à des études du métabolisme musculaire par des techniques d’investigations cellulaires et moléculaires chez des sujets actifs. Ce travail a porté sur l’exercice de haute intensité générant de hauts niveaux de fatigue musculaire et sur les réponses adaptatives qui en résultent au niveau cardio-respiratoire et musculaire. La prise de bicarbonate de sodium contre placebo a permis d’étudier précisément le rôle de l’accumulation de protons au cours de séances de sprints en cyclisme. Grâce à ces travaux, nous avons pu montrer que si une alcalose induite n’améliorait pas systématiquement les performances de sprint en cyclisme, une perturbation importante du pH conduisait à des modifications du transport de l’oxygène pendant l’exercice, du fonctionnement des mitochondries après 24h de récupération, mais également de l’expression de certaines protéines impliquées dans la régulation du pH, à savoir le cotransporteur lactate/proton (MCT1) et sa protéine chaperonne CD147, ainsi que l’échangeur sodium/proton (NHE1). Ces modifications étaient en lien avec une réduction du stress oxydatif par l’alcalose induite, suggérant un rôle délétère de la carbonylation des protéines sur l’expression de ces protéines. Ces résultats permettent d’avoir un nouveau regard sur le rôle de l’acidose dans les mécanismes de régulation au niveau physiologique, cellulaire et moléculaire chez l’Homme.

This thesis falls within the general framework of the energetic physiology, and includes three studies, ranging from global exploration of the humans in motion (field tests with athletes of the French Cycling Team, laboratory exploration during exercise on trained cyclists) to studies of muscle metabolism by techniques of cellular and molecular investigations in active subjects. This work has focused on high-intensity exercise generating high levels of muscle fatigue and the resulting adaptive cardiorespiratory and muscular responses. Supplementation of sodium bicarbonate against placebo was used to study the precise role of the accumulation of protons during sprint cycling sessions. Through this work, we have shown that, if an induced alkalosis did not systematically improve sprint cycling performances, a significant disruption of the pH led to changes in oxygen transport during exercise, in mitochondrial function after 24h of recovery, but also in the expression of some proteins involved in pH regulation (i. E. , lactate/proton co-transporter (MCT1) its chaperone protein CD147, and the sodium/proton exchanger (NHE1)). These changes were related to a reduction of the oxidative stress induced by alkalosis, suggesting a harmful role of the carbonylation in these protein expressions. These results provide a new perspective on the role played by acidosis in the regulatory mechanisms at physiological, cellular and molecular levels in humans.; Ce travail de thèse s’inscrit dans le cadre général de la physiologie énergétique, et comprend trois études, qui vont de l’exploration globale de l’Homme en mouvement (tests de terrain chez des athlètes de l’Equipe de France de Cyclisme, explorations à l’effort en laboratoire chez des cyclistes entrainés) jusqu’à des études du métabolisme musculaire par des techniques d’investigations cellulaires et moléculaires chez des sujets actifs. Ce travail a porté sur l’exercice de haute intensité générant de hauts niveaux de fatigue musculaire et sur les réponses adaptatives qui en résultent au niveau cardio-respiratoire et musculaire. La prise de bicarbonate de sodium contre placebo a permis d’étudier précisément le rôle de l’accumulation de protons au cours de séances de sprints en cyclisme. Grâce à ces travaux, nous avons pu montrer que si une alcalose induite n’améliorait pas systématiquement les performances de sprint en cyclisme, une perturbation importante du pH conduisait à des modifications du transport de l’oxygène pendant l’exercice, du fonctionnement des mitochondries après 24h de récupération, mais également de l’expression de certaines protéines impliquées dans la régulation du pH, à savoir le cotransporteur lactate/proton (MCT1) et sa protéine chaperonne CD147, ainsi que l’échangeur sodium/proton (NHE1). Ces modifications étaient en lien avec une réduction du stress oxydatif par l’alcalose induite, suggérant un rôle délétère de la carbonylation des protéines sur l’expression de ces protéines. Ces résultats permettent d’avoir un nouveau regard sur le rôle de l’acidose dans les mécanismes de régulation au niveau physiologique, cellulaire et moléculaire chez l’Homme.