Etudes cardio : page 8

La luminothérapie peut augmenter les performances

09/11/2014 | Etudes cardio et Accessoires de musculation

 

The Effects of Evening Bright Light Exposure on Subsequent Morning Exercise Performance
Int J Sports Med     A. Thompson

We investigated the effects of evening bright light on the circadian timing of core temperature and morning exercise performance under conditions of high thermal stress. At 20:00 h, 8 males were exposed to a standardised light protocol and thereafter to either polychromatic bright light (2 500 lux at 50 cm, BL) or no light (0 lux, NL) for 30 min. The following morning, intermittent cycling exercise was undertaken followed by a 10 km time-trial in an environmental chamber set to 35°C and 60% relative humidity. Core body temperature was measured throughout. Data were analysed using a within-subjects model and presented as mean±SD. Time of the sleep-trough in core temperature occurred ~1.75 h later following BL (P=0.07). Prior to time-trial, core temperature was 0.27±0.42°C lower in BL (95%CI: −0.02 to 0.57, P=0.07).

The time-trial was completed 1.43±0.63 min (0.98–1.87) faster in BL (P=0.001).

Post time-trial, intestinal temperature was 38.21±0.56°C (37.84–38.57) in BL compared to 38.64±0.42°C (38.34–38.93) in NL (P=0.10). These data provide the first evidence that a 30-min exposure to bright light prior to sleep can influence exercise performance under hot conditions during the subsequent early morning.

L’endurance n’active pas la même cascade catabolique que la force

31/10/2014 | Etudes cardio et Etudes Musculation et Etudes Perte de poids

 

Autophagy is essential to support skeletal muscle plasticity in response to endurance exercise
Anthony M. J. Sanchez   American Journal of Physiology - Regulatory, Integrative and Comparative Physiology Published 15 October 2014 Vol. 307 no. 8, R956-R969

Physical exercise is a stress that can substantially modulate cellular signaling mechanisms to promote morphological and metabolic adaptations. Skeletal muscle protein and organelle turnover is dependent on two major cellular pathways: Forkhead box class O proteins (FOXO) transcription factors that regulate two main proteolytic systems, the ubiquitin-proteasome, and the autophagy-lysosome systems, including mitochondrial autophagy, and the MTORC1 signaling associated with protein translation and autophagy inhibition.

In recent years, it has been well documented that both acute and chronic endurance exercise can affect the autophagy pathway. Importantly, substantial efforts have been made to better understand discrepancies in the literature on its modulation during exercise. A single bout of endurance exercise increases autophagic flux when the duration is long enough, and this response is dependent on nutritional status, since autophagic flux markers and mRNA coding for actors involved in mitophagy are more abundant in the fasted state.

In contrast, strength and resistance exercises preferentially raise ubiquitin-proteasome system activity and involve several protein synthesis factors, such as the recently characterized DAGK for mechanistic target of rapamycin activation.

In this review, we discuss recent progress on the impact of acute and chronic exercise on cell component turnover systems, with particular focus on autophagy, which until now has been relatively overlooked in skeletal muscle. We especially highlight the most recent studies on the factors that can impact its modulation, including the mode of exercise and the nutritional status, and also discuss the current limitations in the literature to encourage further works on this topic.

Différences hormonales entre le cardio HIIT et classique

02/10/2014 | Etudes cardio et Etudes sur les hormones et Etudes Perte de poids

 

Metabolic and hormonal responses to isoenergetic high-intensity interval exercise and continuous moderate-intensity exercise

Jonathan M. Peake   American Journal of Physiology - Endocrinology and Metabolism Published 1 October 2014 Vol. 307 no. 7, E539-E552

This study investigated the effects of high-intensity interval training (HIIT) vs. work-matched moderate-intensity continuous exercise (MOD) on metabolism and counterregulatory stress hormones. In a randomized and counterbalanced order, 10 well-trained male cyclists and triathletes completed a HIIT session [81.6 ± 3.7% maximum oxygen consumption (V̇o2 max); 72.0 ± 3.2% peak power output; 792 ± 95 kJ] and a MOD session (66.7 ± 3.5% V̇o2 max; 48.5 ± 3.1% peak power output; 797 ± 95 kJ). Blood samples were collected before, immediately after, and 1 and 2 h postexercise.

Carbohydrate oxidation was higher (P = 0.037; 20%), whereas fat oxidation was lower (P = 0.037; −47%) during HIIT vs. MOD.

Immediately after exercise, plasma glucose (P = 0.024; 20%) and lactate (P

< 0.01; 5.4×) were higher in HIIT vs. MOD, whereas total serum free fatty acid concentration was not significantly different (P = 0.33). Targeted gas chromatography-mass spectromtery metabolomics analysis identified and quantified 49 metabolites in plasma, among which 11 changed after both HIIT and MOD, 13 changed only after HIIT, and 5 changed only after MOD. Notable changes included substantial increases in tricarboxylic acid intermediates and monounsaturated fatty acids after HIIT and marked decreases in amino acids during recovery from both trials.

Plasma adrenocorticotrophic hormone (P = 0.019), cortisol (P < 0.01), and growth hormone (P < 0.01) were all higher immediately after HIIT. Plasma norepinephrine (P = 0.11) and interleukin-6 (P = 0.20) immediately after exercise were not significantly different between trials. Plasma insulin decreased during recovery from both HIIT and MOD (P < 0.01).

These data indicate distinct differences in specific metabolites and counterregulatory hormones following HIIT vs. MOD and highlight the value of targeted metabolomic analysis to provide more detailed insights into the metabolic demands of exercise.

Impacts du type de cardio sur l’appétit

11/03/2014 | Etudes cardio et Etudes Perte de poids

 

Impacts du type de cardio sur l’appétit

High-intensity intermittent exercise attenuates ad-libitum energy intake
International Journal of Obesity (2014) 38, 417–422;  A Y Sim


Objective:

To examine the acute effects of high-intensity intermittent exercise (HIIE) on energy intake, perceptions of appetite and appetite-related hormones in sedentary, overweight men.


Design:

Seventeen overweight men (body mass index: 27.7±1.6 kg m−2; body mass: 89.8±10.1 kg; body fat: 30.0±4.3%; VO2peak: 39.2±4.8 ml kg−1 min−1) completed four 30-min experimental conditions using a randomised counterbalanced design. CON: resting control, MC: continuous moderate-intensity exercise (60% VO2peak), HI: high-intensity intermittent exercise (alternating 60 s at 100% VO2peak and 240 s at 50% VO2peak), VHI: very-high-intensity intermittent exercise (alternating 15 s at 170% VO2peak and 60 s at 32% VO2peak). Participants consumed a standard caloric meal following exercise/CON and an ad-libitum meal 70 min later. Capillary blood was sampled and perceived appetite assessed at regular time intervals throughout the session. Free-living energy intake and physical activity levels for the experimental day and the day after were also assessed.


Results:

Ad-libitum energy intake was lower after HI and VHI compared with CON (P=0.038 and P=0.004, respectively), and VHI was also lower than MC (P=0.028). Free-living energy intake in the subsequent 38 h remained less after VHI compared with CON and MC (P0.050). These observations were associated with lower active ghrelin (P0.050), higher blood lactate (P0.014) and higher blood glucose (P0.020) after VHI compared with all other trials. Despite higher heart rate and ratings of perceived exertion (RPE) during HI and VHI compared with MC (P0.004), ratings of physical activity enjoyment were similar between all the exercise trials (P=0.593). No differences were found in perceived appetite between trials.


Conclusions:

High-intensity intermittent exercise suppresses subsequent ad-libitum energy intake in overweight inactive men. This format of exercise was found to be well tolerated in an overweight population.

Bénefices d’un entraînement combiné force et endurance chez des footballeurs

18/12/2013 | Etudes cardio et Etudes Musculation

 

L’entraînement combiné de la force et de l’endurance chez de jeunes footballeurs
Science & Sports Available online 12 December 2013     M.A. Khanfir

Objectif

L’objectif de cette étude était de vérifier l’effet d’un entraînement combiné de force et d’endurance spécifiques au football sur la consommation maximale d’oxygène (VO2max), l’économie de course, la vitesse de course, la force maximale et la détente verticale chez de jeunes footballeurs.

Population et méthodes

Dix jeunes footballeurs ont suivi un programme d’entraînement de 8 semaines. Une évaluation avant et après entraînement a permis de dégager les effets de cet entraînement.

Résultat

L’entraînement combiné de force et d’endurance spécifiques au football a permis l’amélioration des qualités physiques des jeunes footballeurs. Nous avons relevé une amélioration significative de VO2max de 4,9 %, une augmentation de la vitesse maximale aérobie de 7,3 %, une amélioration de l’économie de course de 5,7 %, une amélioration de la détente verticale au squat-jump de 15,6 % et au counter-mouvement-jump de 13 %, une augmentation de la force maximale au demi-squat de 60 %, au leg-extension de 40 % et au leg-curl de 49 % ainsi qu’une amélioration de la performance de course sur 5 m de 5,5 % et sur 30 m de 2 %.

Conclusion

Sachant l’importance du travail technico-tactique en football, un entraînement en endurance avec ballon associé à un entraînement spécifique de la force sans problème d’interférence peut présenter une réelle alternative aux entraînements physiques standards.

Quel est le taux d’oxydation des lipides à l’exercice?

18/12/2013 | Etudes cardio et Etudes Perte de poids

 

Stabilité dans le temps du niveau maximal d’oxydation des lipides à l’exercice
J.-F. Brun       Science & Sports Available online 14 December 2013

Introduction

Le niveau maximal d’oxydation des lipides à l’exercice (LIPOXmax) est la puissance à laquelle le rapport d’utilisation oxydative lipides/glucides est maximal lors d’un exercice à plateau sur 45–60 minutes, minimisant le gaspillage de glucides. Il a été démontré que cette mesure est très reproductible d’un jour à l’autre dans des conditions standardisées, quoiqu’elle soit modifiable par de nombreuses situations physiologiques ou pathologiques. Il restait à évaluer la stabilité de ce paramètre sur de plus longues périodes.

Matériels et méthodes

Nous avons recherché cette stabilité sur une base de données personnelle de 1600 calorimétries d’effort incluant des patients qui ne modifiaient pas leur exercice ou leurs habitudes alimentaires, re-testés après un intervalle moyen de 30 mois. Les patients (n = 11) représentaient une grande variété d’âge (28–74 ans), d’indice de masse corporelle (de 22 à 46,7 kg/m2) et d’aptitude aérobie.

Résultats

Leur LIPOXmax variait entre 18 à 123 watts et leur débit maximal d’oxydation des lipides (DMOL) se situait entre 75 et 423 mg/min. On note une stabilité remarquable du LIPOXmax exprimé en puissance brute (r = 0,993, P < 0,001 ; Bland Altman : différence moyenne −2,36, intervalle de confiance (IC) : [−3,33 à 8,06]. Le DMOL était moins reproductible au cours de ces longues périodes de temps (r = 0,694, P < 0,02 ; différence moyenne 4, IC : [−53 à 61]).

Conclusion

Par conséquent, la puissance à laquelle l’oxydation des lipides est maximale au cours de l’exercice reste stable sur une période moyenne de 30 mois si les habitudes alimentaires et l’exercice ne sont pas modifiés.

Le cardio HIT ne booste pas le métabolisme post-effort

30/11/2013 | Etudes cardio et Echauffement et blessures et Etudes Musculation et Etudes Perte de poids

 

The impact of high-intensity intermittent exercise on resting metabolic rate in healthy males.
Eur J Appl Physiol. 2013 Dec;113(12):3039-47.    Kelly B

High-intensity intermittent exercise training (HIT) may favourably alter body composition despite low training volumes and predicted energy expenditure (EE).

PURPOSE:To characterise the acute impact of two common HIT protocols on EE and post-exercise oxygen consumption (11 h EPOC).
METHODS: Oxygen consumption (l min(-1)), respiratory exchange ratio (RER) and EE were measured in nine healthy, lean males over 12 h under three conditions: control (CON), HIT1 (10 × 1 min high-intensity cycling bouts followed by 1 min rest) and HIT2 (10 × 4 min high-intensity cycling bouts followed by 2 min rest).
RESULTS: Total exercise period EE during HIT1 (1,151 ± 205 kJ) (mean ± SD) was significantly lower than HIT2 (2,788 ± 322 kJ; p

< 0.001).

EE within the 60 min after exercise was significantly albeit marginally higher after HIT1 (388 ± 44 kJ; p = 0.02) and HIT2 (389 ± 39 kJ; p = 0.01) compared with CON (329 ± 39 kJ), with no difference between exercise conditions (p = 0.778). RER during this period was significantly lower in HIT1 (0.78 ± 0.06; p = 0.011) and HIT2 (0.76 ± 0.04; p = 0.004) compared with CON (0.87 ± 0.06). During the ‘slow phase’ of EPOC (1.25-9.75 h), there were no significant differences in EE (p = 0.07) or RER (p = 0.173) between trials.

CONCLUSIONS:Single HIT sessions notably increases EE during exertion; however, the influence on metabolic rate post-exercise is transient and relatively minor.

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