No description available.

O objetivo deste estudo foi avaliar o efeito da manipulação do espaço (dimensão da quadra) de jogo reduzidos (JRs) na demanda física, fisiológica e perceptual em jovens jogadores de basquetebol. Doze jogadores da categoria sub19 (18,6 ± 0,5 anos, 88,8 ± 14,5 kg e 192,6 ± 6,5 cm) participaram voluntariamente do estudo. Todos os atletas realizaram os dois protocolos de JRs, em dias distintos (procedimento cross-over); a variável manipulada nos JRs foi o espaço de jogo (dimensão da quadra). No primeiro protocolo, o JR foi realizado em uma quadra com tamanho oficial (28x15m; JR28x15), e no segundo, em uma quadra com a largura reduzida, 28x9m (JR28x9). Os JRs foram realizados em uma dinâmica de 3x3 (3 jogadores em cada equipe), com 4 períodos de 4 minutos intercalados por 3 minutos de intervalo. Antes e após os JRs foram realizados os testes de sprints repetidos (TSR; 12 sprints de 20m com 20s de intervalo entre os sprints) e salto vertical (SV). Amostras de sangue para a análise da concentração de lactato [Lac] foram coletadas, a) antes do jogo (Pré-JR), b) imediatamente após o jogo (Pós-JR), c) depois do TSR após o JR (Pós-TSR-JR), e d) 30 minutos após o término do JR (Pós-30min). A frequência cardíaca (FC) foi registrada durante todo o jogo em ambos os protocolos e utilizada, posteriormente, para o cálculo do \"impulso de treinamento\" (TRIMP); 30 minutos após o término dos JRs os jogadores registraram a percepção subjetiva do esforço da sessão (PSE da sessão). Uma medida de carga interna de treinamento (CIT) foi gerada e registrada através do método da PSE da sessão. Para análise dos dados, utilizou-se uma ANOVA de medidas repetidas de dois fatores (Protocolos de JR x Momento) para avaliar o desempenho nos testes físicos, [Lac] e a FC medida em cada período de jogo e intervalos de recuperação. Para a análise da FC média, PSE da sessão, TRIMP e CIT foi utilizado um test t de student para amostras pareadas. O nível de significância foi estabelecido em 5%. O tamanho de efeito foi estimado através do d de Cohen. Não foram observadas diferenças do momento pré para pós, como também entre os protocolos de JR para as variáveis de desempenho dos testes físicos; a [Lac] apresentou um aumento do momento pré-JR para pós-JR, sem diferença estatística entre os protocolos. Foram observados valores médios de 88,1 ± 3,2% e 90,2 ± 3,1% para FC relativa (%FC pico), 97,3 ± 4,9 e 100,5 ± 7,8 UA para TRIMP, 171,9 ± 31,2 e 172,2 ± 29,2 UA para CIT, 7,2 ± 1,4 e 6,7 ± 1,3UA para a PSE da sessão e 5,4 ± 2,6 e 5,9 ± 2 mmol·l-1 para a [Lac] pós-JR (JR28x15 e JR28x9, respectivamente). Porém não foram observadas diferenças significantes entre os protocolos para nenhumas das medidas apresentadas. Os resultados do presente estudo indicam que: 1) a manipulação do espaço não acarreta em diferentes respostas psicofisiológicas; 2) a demanda induzida pelo JRs não foi suficiente para induzir uma queda na capacidade de desempenho de sprints repetidos e no salto vertical; 3) a demanda induzida pelo JR nos parâmetros psicofisiológicos foi similar aquela reportada para jogos oficiais / The aim of the study was to analyze the effect of court size manipulation of smallsided games (SSG) on physical, physiological and perceptual demand in young basketball athletes. Twelve players from an under-19 team (18.6 ± 0.5 yrs, 88.8 ± 14.5 kg e 192.6 ± 6.5 cm) voluntarily participated in this study. All athletes performed two SSG protocols in different days (cross-over design); the manipulated variable was court area. In the first protocol, SGG was played at official court area (28x15m; SSG28x15), and in the second protocol was played at a court with reduced width area (28x9m; SSG28x9). SSG\'s were performed with a 3-a-side dynamic, with four game periods of four minutes, and three minutes of active rest between periods. Before and after SSG players were submitted to a repeated sprint test (RST; 12sprints of 20m with 20s recovery) and a vertical jump test. Blood samples were provided to lactate concentration [Lac] analysis at: a) before game (Pre-SSG), b) Immediately after game (Post-SSG), c) after RST performed post SSG (Post-RSTSSG), and d) 30 minutes after SSG (Post-30min). The heart rate (HR) was monitored during the SSG and used to calculate SSG mean HR and to calculate training impulse (TRIMP); 30 minutes after the ending of SSG player answered the rate of perceived exertion of the session (Session-RPE). Internal training load (ITL) was calculated by the Session-RPE method. For data analysis a Two-way ANOVA with repeated measures (SSG\'s protocols x Moments) was conducted to evaluate tests performance, [Lac], and mean HR for each game period and rest interval. In order to analyze the game\'s mean HR, Session-RPE, TRIMP and ITL were utilized a student t-test for repeated measures. The significance level was set at 5%. Effect size was estimate through Cohen\'s d. No statistical difference was observed between pre and post measures, or between protocols to tests performance variables. [Lac] showed and increased from pre-SSG to post-SSG, with no difference between protocols. Psychophysiological variables present mean values of 88.1 ± 3.2% and 90.2 ± 3.1% to relative HR (% peak HR), 97.3 ± 4.9 and 100.5 ± 7.8 AU to TRIMP, 171.9 ± 31.2 and 172.2 ± 29.2 AU to ITL, 7.2 ± 1.4 and 6.7 ± 1.3 AU to Session-RPE and 5.4 ± 2.6 and 5.9 ± 2 mmol·l-1 to Post-SSG [lac] (SSG28x15 and SSG28x9, respectively). However, it was not observed any difference between SSG protocols and any measure. The results from the present study indicates: 1) Court size manipulation does not elicit different psychophysiological responses; 2) SSG demand was not sufficient to impair repeated sprints ability or jump ability; 3)SSG psychophysiological demand was similar to those reported to official basketball games

Consumption of supplements and energy drinks is common among athletes; however, there is a lack of research on the efficacy of energy drink consumption before and during short-duration, intense exercise. The purpose of this research was to investigate the acute effects of a low-calorie, caffeine-taurine, energy drink (AdvoCare Spark®) on repeated sprint performance and anaerobic power in National Collegiate Athletic Association Division I football players. Twenty well-trained Division I football players (age: 19.7 ± 1.8 years, height: 184.9 ± 5.3 cm, weight: 100.3 ± 21.7 kg) participated in a double-blind, randomized crossover study in which they received the energy drink or an isoenergetic, isovolumetric, noncaffeinated placebo. The two trials were separated by 7 days. The Running Based Anaerobic Sprint Test (RAST), consisting of six 35-m sprints with 10 s of rest between each sprint, was used to assess anaerobic power. Sprint times were recorded with an automatic electronic timer. On average, there iv was no statistically significant difference between the placebo (15.06 ± 3.80 W·s-1) and beverage (15.3 ± 4.18 W·s-1) measurements of fatigue index. Neither were there statistically significant main effects of the beverage treatment on power F(1, 18) = 3.84, p = 0.066; or sprint time F(1, 18) = 3.06, p = 0.097. However, there was a significant interaction effect between caffeine use and the beverage for sprint times (F = 4.62, p = 0.045), as well as for anaerobic power (F = 5.40, p = 0.032), indicating a confounding effect. In conclusion, a caffeine-taurine energy drink did not improve the sprint performance or the anaerobic power of collegiate football players, but the level of caffeine use by the athletes likely influenced the effect of the drink.

A small number of previous cross-sectional studies have examined the relationship between endurance training status on recovery of performance and metabolites from sprinting. However, no longitudinal studies have been undertaken. In addition, there is a dearth of information on female subjects and on running exercise which prompted the need, in the present thesis, to address the effect of menstrual cycle phase on performance and metabolic responses during a repeated sprint run. Thus, the overall purpose of the present thesis was to examine the effect of short-term endurance training on a repeated sprint in female subjects. A number of methodological studies (for which 25 subjects volunteered) were undertaken as preparation for the main experimental chapters of the thesis (Chapter 3). The first methodological study examined the reliability of performance during a 30-s sprint on the non-motorised treadmill. Performance was reproducible as indicated by the 95% limits of agreement for PPO (5 ± 42 W) and by the ratio limits of agreement for MPO (1.01 */÷1.06) during the 30 s sprint. In the second methodological study it was found that capillary lactate concentrations were significantly higher than venous blood lactate after a 30 s sprint (P < 0.05). The third methodological study revealed that a repeated sprint run caused an additional plasma volume loss when compared with the loss caused by a change in posture alone (12.7 % vs 7.5 % for sprint and posture change, respectively, P < 0.05). Finally, it seems that prolonged freezing (up to 13 months) does not have a detrimental influence on whole blood lactate concentration, but repeated defrosting may result in errors in the determination of blood lactate at high lactate concentrations (methodological study 4). The first mam experiment examined the effects of menstrual cycle phase on performance and metabolic responses during a repeated sprint run (2x30 s, with a 2 min passive recovery) in 8 volunteers (chapter 4). Performance was unaltered during the follicular, mid-cycle and luteal phase of the menstrual cycle as reflected by PPO (461 ± 51 and 395 ± 48, 443 ± 43 and 359 ± 44, 449 ± 52 and 397 ± 48 W, for the first and second sprint, during the follicular, mid-cycle and luteal phase, respectively, P > 0.05) and MPO (302 ± 41 and 252 ± 29, 298 ± 37 and 248 ± 29, 298 ± 39 and 252 ± 35 W, for the first and second sprint, at follicular, mid-cycle and luteal phases, respectively, P > 0.05). Similarly, blood metabolic responses were unaffected by menstrual cycle phase as reflected by the unchanged metabolic profile of blood lactate, plasma' ammonia, blood pH and % changes in plasma volume across menstrual cycle. These results suggest that the hormonal fluctuations of 17-,β-estradiol (estradiol) and progesterone, due to menstrual cycle phase, have no effect on repeated sprint performance and possibly on the metabolic responses as reflected by the blood metabolic responses. The second main experiment examined the effects of short-term endurance training on power output recovery and metabolic responses to a repeated sprint run (2x30 s with a 2 min passive recovery) (chapter 5, n = 16). Six weeks of endurance training resulted in a 3% increase (P < 0.05) in V̇ 0₂ max (from 48.7 ± 4.4 before training to 50.17 ± 5.1 mL.kg⁻¹·min⁻¹ after training) in the training group (n = 8) in comparison with 1.9% decrease (from 50.4 ± 1.3 to 49.4 ± 1.2 mL.kg⁻¹·min⁻¹ post-trial) in the control group (n = 7). In addition, % V̇ 0₂ max @ 4 mmol·L⁻¹ [the relative intensity (% V̇ 0₂ max) corresponding to blood lactate concentration of 4 mmol·L⁻¹] was 3% higher (from 82 to 84%) in the training group as compared with the 1% decrease in the control group (from 81 to 80%) (P < 0.05). These endurance adaptations were accompanied by a 7% improvement in MPO recovery (in the second of two 30 s sprints) in the training group in comparison with 2% increases in the control group after training (P < 0.05). Metabolic responses to sprints were unaltered after training, but there was a tendency for higher pH immediately after sprint 1 in the training group in comparison with the control group (7.12 ± 0.07 vs 7.19 ± 0.06 and 7.09 ± 0.07 vs 7.10 ± 0.06, before and after training, in the training and control group, respectively, P = 0.082). These findings suggest that endurance training can be beneficial in terms of quicker recovery of performance during a repeated sprint run. The third main experiment examined the effects of endurance training on performance recovery and muscle metabolites (chapter 6, n=14). Endurance training resulted in a tendency towards lower blood lactate concentrations during sub-maximal exercise in the training group in comparison with the control group (P = 0.063) whilst time to exhaustion for the incremental V̇ 0₂ max test was 12.7% longer for the training group in comparison with 4.1% decrease in the control group (P = 0.095). These endurance training adaptations were accompanied by a 7% improvement (77 ± 7 to 84 ± 5 W) in MPO recovery in the second of two 30 s sprints in the training group while in the control group MPO recovery improved by just 2% (87 ± 8 to 89 ± 8%) (P < 0.05). In addition, similar increases in the recovery of peak speed (3.4% vs 1%, P < 0.05), and mean speed (5% vs 0.9%, P < 0.05) were also evident in the training in comparison with control group. Endurance training resulted in 5.6% decrease in ATP provision from PCr degradation ≈ 14 s post-sprint 1 (P < 0.05) while glycogen degradation was 10% lower (P = 0.063). The latter alterations, in turn, resulted in a tendency towards less reliance on anaerobic energy resources for energy supply after training in the training group (11%, P = 0.098). These results corroborate the findings of chapter 5, but it is still unclear which physiological mechanisms were instrumental in enhancing recovery of performance. It is possible that a faster initial PCr resynthesis or an improved mechanical efficiency or an increased reliance on aerobic metabolism, independently, all together, or in any combination, could have contributed to these improvements in performance recovery. In conclusion the present thesis has shown that: the non-motorised treadmill is a reliable tool for the examination of sprint running performance in the laboratory; that performance and metabolic responses during a repeated sprint run are unaffected by menstrual cycle phase and; that endurance training enhances the recovery of power in female subjects during a repeated sprint run of 2 x 30 s duration with a 2 min passive recovery. The mechanisms underlying the performance improvement following endurance training are unknown, but it is possible that faster PCr resynthesis during the initial phase of recovery (< 1 min) after the sprint is the dominant factor, while greater reliance on aerobic metabolism and improved mechanical efficiency can not be excluded.

The purpose of the present study was to examine the time-course of mechanical power output and neuromuscular activity during fatiguing repeated-sprint exercise and recovery in man. Prior to the main study, we also investigated the reproducibility of power output during a single 6-s cycling sprint. For this study, eleven healthy moderately trained males performed a 6-s standing sprint on the front-access cycle ergometer on four separate occasions. The results of the study showed that reliable power outputs can be obtained after one familiarization session in subjects unfamiliar with maximal cycling sprint exercise. However, the inclusion of an extra familiarization session ensured more stable power outputs. Therefore, two trials should allow adequate familiarization with the maximal 6-s cycling test. For the main study, eight young moderately trained adult men performed an exercise protocol that consisted of ten, 6-s sprints on a wind-braked cycle ergometer interspersed with 30 s of recovery. After 6 min of passive recovery, five, 6-s sprints were repeated, again interspersed by 30 s of recovery. Peak power output (PPO) and mean power output (MPO) were measured during each sprint and EMG data (i.e., RMS) from the vastus lateralis muscle were also recorded. A one-way ANOVA with repeated measures (i.e., sprint number) was used to allocate the significant differences in each dependent variable over time. Analysis revealed a decline in power output during the fatiguing exercise that was accompanied by a decrease in EMG amplitude of the vastus lateralis muscle. Six minutes after the fatiguing exercise, power output during sprint 11 significantly recovered with respect to values recorded in sprint 10, but remained significantly lower than that recorded in the initial sprint. Thus, 6 min was insufficient to fully recover from the fatiguing repeated sprint protocol utilised in this study. The main findings in the present study were that: 1) the partial recovery of power output in sprint 11 was not accompanied by the recovery V of EMG amplitude; 2) similar mean power outputs were recorded during sprint 4 and 11 despite a significantly lower EMG activity recorded during the latter sprint; and 3) despite comparable mean power outputs during sprint 4 and 11, the decrease in power output over the next five sprints was greater for sprints 11 to 15 than for sprints 4 to 8.

O objetivo deste estudo foi avaliar o efeito da manipulação do espaço (dimensão da quadra) de jogo reduzidos (JRs) na demanda física, fisiológica e perceptual em jovens jogadores de basquetebol. Doze jogadores da categoria sub19 (18,6 ± 0,5 anos, 88,8 ± 14,5 kg e 192,6 ± 6,5 cm) participaram voluntariamente do estudo. Todos os atletas realizaram os dois protocolos de JRs, em dias distintos (procedimento cross-over); a variável manipulada nos JRs foi o espaço de jogo (dimensão da quadra). No primeiro protocolo, o JR foi realizado em uma quadra com tamanho oficial (28x15m; JR28x15), e no segundo, em uma quadra com a largura reduzida, 28x9m (JR28x9). Os JRs foram realizados em uma dinâmica de 3x3 (3 jogadores em cada equipe), com 4 períodos de 4 minutos intercalados por 3 minutos de intervalo. Antes e após os JRs foram realizados os testes de sprints repetidos (TSR; 12 sprints de 20m com 20s de intervalo entre os sprints) e salto vertical (SV). Amostras de sangue para a análise da concentração de lactato [Lac] foram coletadas, a) antes do jogo (Pré-JR), b) imediatamente após o jogo (Pós-JR), c) depois do TSR após o JR (Pós-TSR-JR), e d) 30 minutos após o término do JR (Pós-30min). A frequência cardíaca (FC) foi registrada durante todo o jogo em ambos os protocolos e utilizada, posteriormente, para o cálculo do \"impulso de treinamento\" (TRIMP); 30 minutos após o término dos JRs os jogadores registraram a percepção subjetiva do esforço da sessão (PSE da sessão). Uma medida de carga interna de treinamento (CIT) foi gerada e registrada através do método da PSE da sessão. Para análise dos dados, utilizou-se uma ANOVA de medidas repetidas de dois fatores (Protocolos de JR x Momento) para avaliar o desempenho nos testes físicos, [Lac] e a FC medida em cada período de jogo e intervalos de recuperação. Para a análise da FC média, PSE da sessão, TRIMP e CIT foi utilizado um test t de student para amostras pareadas. O nível de significância foi estabelecido em 5%. O tamanho de efeito foi estimado através do d de Cohen. Não foram observadas diferenças do momento pré para pós, como também entre os protocolos de JR para as variáveis de desempenho dos testes físicos; a [Lac] apresentou um aumento do momento pré-JR para pós-JR, sem diferença estatística entre os protocolos. Foram observados valores médios de 88,1 ± 3,2% e 90,2 ± 3,1% para FC relativa (%FC pico), 97,3 ± 4,9 e 100,5 ± 7,8 UA para TRIMP, 171,9 ± 31,2 e 172,2 ± 29,2 UA para CIT, 7,2 ± 1,4 e 6,7 ± 1,3UA para a PSE da sessão e 5,4 ± 2,6 e 5,9 ± 2 mmol·l-1 para a [Lac] pós-JR (JR28x15 e JR28x9, respectivamente). Porém não foram observadas diferenças significantes entre os protocolos para nenhumas das medidas apresentadas. Os resultados do presente estudo indicam que: 1) a manipulação do espaço não acarreta em diferentes respostas psicofisiológicas; 2) a demanda induzida pelo JRs não foi suficiente para induzir uma queda na capacidade de desempenho de sprints repetidos e no salto vertical; 3) a demanda induzida pelo JR nos parâmetros psicofisiológicos foi similar aquela reportada para jogos oficiais / The aim of the study was to analyze the effect of court size manipulation of smallsided games (SSG) on physical, physiological and perceptual demand in young basketball athletes. Twelve players from an under-19 team (18.6 ± 0.5 yrs, 88.8 ± 14.5 kg e 192.6 ± 6.5 cm) voluntarily participated in this study. All athletes performed two SSG protocols in different days (cross-over design); the manipulated variable was court area. In the first protocol, SGG was played at official court area (28x15m; SSG28x15), and in the second protocol was played at a court with reduced width area (28x9m; SSG28x9). SSG\'s were performed with a 3-a-side dynamic, with four game periods of four minutes, and three minutes of active rest between periods. Before and after SSG players were submitted to a repeated sprint test (RST; 12sprints of 20m with 20s recovery) and a vertical jump test. Blood samples were provided to lactate concentration [Lac] analysis at: a) before game (Pre-SSG), b) Immediately after game (Post-SSG), c) after RST performed post SSG (Post-RSTSSG), and d) 30 minutes after SSG (Post-30min). The heart rate (HR) was monitored during the SSG and used to calculate SSG mean HR and to calculate training impulse (TRIMP); 30 minutes after the ending of SSG player answered the rate of perceived exertion of the session (Session-RPE). Internal training load (ITL) was calculated by the Session-RPE method. For data analysis a Two-way ANOVA with repeated measures (SSG\'s protocols x Moments) was conducted to evaluate tests performance, [Lac], and mean HR for each game period and rest interval. In order to analyze the game\'s mean HR, Session-RPE, TRIMP and ITL were utilized a student t-test for repeated measures. The significance level was set at 5%. Effect size was estimate through Cohen\'s d. No statistical difference was observed between pre and post measures, or between protocols to tests performance variables. [Lac] showed and increased from pre-SSG to post-SSG, with no difference between protocols. Psychophysiological variables present mean values of 88.1 ± 3.2% and 90.2 ± 3.1% to relative HR (% peak HR), 97.3 ± 4.9 and 100.5 ± 7.8 AU to TRIMP, 171.9 ± 31.2 and 172.2 ± 29.2 AU to ITL, 7.2 ± 1.4 and 6.7 ± 1.3 AU to Session-RPE and 5.4 ± 2.6 and 5.9 ± 2 mmol·l-1 to Post-SSG [lac] (SSG28x15 and SSG28x9, respectively). However, it was not observed any difference between SSG protocols and any measure. The results from the present study indicates: 1) Court size manipulation does not elicit different psychophysiological responses; 2) SSG demand was not sufficient to impair repeated sprints ability or jump ability; 3)SSG psychophysiological demand was similar to those reported to official basketball games

The critical power (CP) concept has been used to determine the appropriate rest interval during intermittent exercise through the investigation of critical rest interval (CRI). Repeated sprint ability (RSA) testing has been developed to define the athlete’s ability to recover and maintain maximal effort during successive bouts. The CP model has been used to understand the physiological responses involved with intermittent exercise delineating between severe and heavy exercise intensity domains. The primary purpose of this study was to determine the CRI from the work-time relationship given by RSA testing using varying work to rest ratios. The secondary purpose was to determine the validity of CRI by evaluation of physiological responses above and below estimated rest interval values during intermittent cycling. Twelve recreationally trained males (mean ± SD; age 24.1 ± 3.6yr; height 175.8 ± 7.0cm; weight 77.6 ± 12.8kg; V̇ O2peak 43.3 ± 5.6ml/kg/min; Body Fat (%) 24.5 ± 4.4) were recruited for this study. Participants performed a graded exercise test to determine V̇ O2peak and peak heart rate. Eight participants completed the same three RSA protocols with 6s maximal sprints and varying rest intervals (12-24s) on a cycle ergometer. Intermittent critical power (ICP) was calculated through the linear total work (TW) and time-to-exhaustion (TTE) relationship, whereas CRI was estimated using the average work per sprint and ICP. Seven subjects completed trials above and below estimated CRI to evaluate the validity of this estimate through the examination of the physiological responses. Breath-by-breath oxygen consumption (V̇ O2) and heart rate (HR) values were recorded during the validation trials. One-way repeated measures analysis of variance (ANOVA) was used to analyze the variables from the RSA trials. Paired samples t-tests were performed to compare performance and physiological variables above or below CRI during the validation trials. Two-way repeated measures ANOVA was used to examined the changes in oxygen consumption (V̇ O2), HR, mean power (MP), and TW throughout the validation trials. Significant differences (p < 0.1) were found for the number of intervals completed, TTE, average work per sprint, peak and mean V̇ O2 between RSA protocols. Linearity between TW and TTE was r2 = 0.952 ± 0.081. During the validation trials, TTE was significantly greater in the above versus the below CRI trial (2270.43 ± 941.15s vs. 1511.00 ± 811.0s). Furthermore, blood lactate concentration (8.94 ± 4.89mmol/L vs. 6.56 ± 3.45mmol/L), AveV̇ O2 (2.05 ± 0.36L/min vs. 1.78 ± 0.26L/min), V̇ O2peak (2.84 ± 0.48L/min vs. 2.61 ± 0.43L/min), and AveHR (151.14 ± 18.46bpm vs. 138.14 ± 17.51L/min) were significantly greater in the below CRI trial when compared to the above CRI trial. Significant interactions were found between above and below trials within minimal V̇ O2 response (F = 6.886, p = 0.024, η2 = 0.534) to the recovery intervals and maximal HR (F = 4.51, p = 0.016, η2 = 0.429) response to the work intervals. During the above CRI trial, minimal V̇ O2 response decreased over time (51-43%V̇ O2 peak) while maximal HR response achieved a steady state level (81-84%HRpeak). Conversely, minimal V̇ O2 response during the below CRI trial achieved a steady state level (54-58%V̇ O2 peak), whereas maximal HR response increased over time (84-90%HRpeak). The relationship between TW and TTE is appropriate for use with RSA testing with varying rest intervals. The differing physiological response during the validation trials may reflect changes in energy system contribution. In conclusion, CRI distinguished between physiological responses related to exercise intensity domains in a manner similar to CP estimates determined from other testing and exercise modalities.

No description available.

Cette thèse porte sur l’étude des mécanismes de régulation du niveau de fatigue périphérique à l’exercice et sur les conséquences de cette régulation sur la capacité de performance motrice. Nous avons tout d’abord démontré que la puissance est étroitement régulée au cours de sprints répétés – épreuve au cours de laquelle la commande motrice est recrutée à son niveau maximal volontaire – de sorte qu’un seuil critique de fatigue périphérique ne soit jamais dépassé. Nous avons ensuite montré qu’il existe un lien étroit entre l’atteinte de ce seuil critique de fatigue et l’arrivée à une phase de plateau de puissance développée au cours de sprints répétés, indépendamment de la durée de la récupération entre les sprints. Ces résultats ont permis de démontrer que le niveau d'activité de la commande motrice centrale et la puissance sont régulés au cours de sprints répétés dans le but de limiter le niveau de fatigue périphérique à un niveau seuil. Le rôle de ce mécanisme régulateur est cependant dépendant de la nature de la tâche. Nous avons en effet montré que l’arrêt de l’effort d’un exercice de squat isométrique, conduit jusqu'à épuisement, est associé à une défaillance de l’activation centrale volontaire, qui précède l'atteinte du seuil critique de fatigue. Enfin, l'application de ces données et concepts théoriques à l'exercice réalisé sur une plateforme à instabilité servo-assistée (imoove) a permis de montrer que ce type d’outil permet un recrutement accru des muscles posturaux et de l’équilibre comparé à un exercice réalisé sur une surface stable, sans compromettre la fatigue et le recrutement des muscles locomoteurs, déterminants des adaptations positives à l'entraînement. / This doctorate thesis focused on the mechanisms involved in the control of peripheral fatigue during exercise and on the consequences of this regulation on exercise tolerance. We first demonstrated that performance during repeated sprints – a trial during which the central motor drive is activated at its maximal voluntary level – is tightly regulated to avoid the development of peripheral fatigue beyond a critical threshold. We then showed that the attainment of the plateau phase of performance, characterized by a constant power output until the last sprint, was closely linked to the attainment of the critical threshold of peripheral fatigue, independently of the recovery duration between sprints. These firsts results demonstrated that central motor drive and power output are regulated during repeated sprints in order to limit the development of peripheral fatigue beyond a critical threshold. However, the role of this regulatory mechanism is task-dependent. Indeed, we showed that time to task failure during the first repetitions of a sustained submaximal isometric contraction is likely associated with failure in central activation of motor units, which precede the attainment of the critical threshold of peripheral fatigue. We then developed applied research protocols on imoove, a servo-assisted instability device for training composed by a board that can move in the three-dimensional plans. Because greater trunk and ankle muscles activity was achieved in imoove without compromising lower limb muscles activity and fatigue, this device may provide sufficient muscle overload to simultaneously develop locomotor, postural and balance muscles.