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Attention au cardio dans le froid si vous avez du mal à contrôler votre appétit!

19/12/2014 | Etudes Perte de poids

 

Effects of Exercise in the Cold on Ghrelin, PYY, and Food Intake in Overweight Adults
Medicine & Science in Sports & Exercise: January 2015 - Volume 47 - Issue 1 - p 49–57     CRABTREE, DANIEL R

Purpose: Exercise in cold water has been shown to simulate postexercise energy intake (EI) in normal-weight individuals. However, the effect of cold exercise on EI in overweight individuals has yet to be examined. The present study investigated the effect of brisk walking in a cold (8°C) and neutral (20°C) environment on postexercise EI and appetite hormone responses.

Methods: Sixteen overweight participants (10 men and six women; age, 50.1 ± 11.6 yr; body mass index, 28.9 ± 4.2 kg·m−2) completed a 45-min treadmill walk at 8°C and 20°C in a randomized counterbalanced design. Participants were presented with an ad libitum buffet meal 45 min after exercise, and EI was covertly measured. Skin and rectal temperature were monitored throughout exercise and for 30 min after exercise, and concentrations of the appetite hormones total ghrelin, acylated ghrelin, and total peptide YY were assessed before and after exercise and before and after meal.

Results: EI was significantly greater after exercise in the cold (1299 ± 657 kcal (mean ± SD)) compared with that after exercise in the neutral environment (1172 ± 537 kcal (mean ± SD)) (P < 0.05). The change in the acylated ghrelin concentrations and the acylated ghrelin AUC values were significantly greater during walking in the cold versus those during walking in the neutral condition (P < 0.05).

Conclusions: These findings show that in overweight individuals, exercise in the cold stimulates postexercise EI to a greater extent than exercise in a neutral environment.

Comment la caféine facilite t’elle l’effort?

19/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids

 

Cortical substrates of the effects of caffeine and time-on-task on perception of effort
Helma M. de Morree       Journal of Applied Physiology Published 15 December 2014 Vol. 117 no. 12, 1514-1523

Caffeine intake results in a decrease in perception of effort, but the cortical substrates of this perceptual effect of caffeine are unknown. The aim of this randomized counterbalanced double-blind crossover study was to investigate the effect of caffeine on the motor-related cortical potential (MRCP) and its relationship with rating of perceived effort (RPE). We also investigated whether MRCP is associated with the increase in RPE occurring over time during submaximal exercise.

Twelve healthy female volunteers performed 100 intermittent isometric knee extensions at 61 ± 5% of their maximal torque 1.5 h after either caffeine (6 mg/kg) or placebo ingestion, while RPE, vastus lateralis electromyogram (EMG), and MRCP were recorded. RPE and MRCP amplitude at the vertex during the first contraction epoch (0–1 s) were significantly lower after caffeine ingestion compared with placebo (P < 0.05) and were significantly higher during the second half of the submaximal intermittent isometric knee-extension protocol compared with the first half (P < 0.05). No significant effects of caffeine and time-on-task were found for EMG amplitude and submaximal force output variables.

The covariation between MRCP and RPE across both caffeine and time-on-task (r10 = −0.335, P < 0.05) provides evidence in favor of the theory that perception of effort arises from neurocognitive processing of corollary discharges from premotor and motor areas of the cortex.

Caffeine seems to reduce perception of effort through a reduction in the activity of cortical premotor and motor areas necessary to produce a submaximal force, and time-on-task has the opposite effect.

La réponse cardiaque à la caféine est imprévisible!

18/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Caffeine With and Without Sugar: Individual Differences in Physiological Responses During Rest
Rush Elaine             Journal of Caffeine Research. December 2014, 4(4): 127-130.

Background: The consumption of caffeine with and without sugar is endemic, but little is known about variation in individual physiological responses at rest. We have previously shown that the ingestion of caffeine with sugar increased the rate of carbon dioxide production more than when sugar alone was consumed.

Objective: The aim of this study was to determine the effect of the ingestion of caffeine, sugar, and caffeine with sugar on carbon dioxide production and heart rate.

Methods: In a crossover three-treatment design, 12 participants reported fasting on three separate days. Treatments were 1.33 mg/kg body weight caffeine only, 0.4 g/kg body weight sugar only, and caffeine with sugar. Breath-by-breath measurements of respiratory gas exchange and heart rate were recorded for 30 min before and after treatments. Data visualization techniques were used to examine the patterns of response.

Results: Carbon dioxide production increased or remained the same with all three treatments. Caffeine alone slowed the heart rate of eight participants and remained the same for four participants. Sugar alone either increased (n=8) or did not change the heart rate (n=4). Caffeine with sugar either decreased (n=5), did not change (n=6), or increased the heart rate (n=1). The intraindividual variability in response to treatments did not show a consistent pattern and could not be associated with habitual caffeine consumption, gender, or physical activity level.

Conclusions: The physiological response to caffeine with and without sugar varied widely. Effects of caffeine phenotypes, physical activity levels, habitual intake, and metabolic responses, including markers of de novo lipogenesis, need further investigation.

La caféine: bonne pour le foie?

18/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids

 

The Relationship between Coffee Drinking and Liver Function Tests in Korean Men
Park Kwang Rae           Journal of Caffeine Research. December 2014, 4(4): 131-137.

Background: Coffee is known to have a protective effect on liver enzymes. There are a limited number of Asian studies on this subject. We investigated the relationship between coffee and liver function tests in Korean men on a large scale.

Methods: Study participants were consecutive men who had a regular health checkup in a university hospital in Korea. Information on coffee intake, alcohol drinking, and smoking was collected through self-administered questionnaires.

Results: A total of 3,844 men were enrolled in this study. Coffee drinking was positively associated with smoking and alcohol drinking. Coffee drinking was inversely associated with aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) concentrations (r=−1.33, p=0.008 and r=−6.35, p=0.007, respectively). Also, increasing levels of coffee consumption was inversely associated with AST and GGT in a multivariate model (p<0.001 and p<0.001, respectively). The relationship between coffee drinking status and alanine aminotransferase (ALT) did not reach statistical significance. However, heavy coffee consumption (≥3 cups/day) was significantly inversely related to ALT compared with mild coffee consumption (<1 cup/day) and non-coffee drinkers in multivariate analyses (p=0.032). All multivariate models were adjusted for age, body mass index, regular exercise, smoking amount, and alcohol drinking status.

Conclusions: Coffee drinking was inversely associated with AST and GGT in apparently healthy Korean men. The relationship showed a dose–response pattern. It was suggested that ALT was lower in heavy coffee consumers (≥3 cups/day) compared with mild coffee consumers (<1 cup/day) and non-coffee drinkers.

La capsaïcine aide la chimio contre les cancers de la prostate

16/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Capsaicin: A novel radio-sensitizing agent for prostate cancer
Natalie A. Venier                   The Prostate Volume 75, Issue 2, pages 113–125, February 2015

Radio-sensitizing agents sensitize tumor cells to the lethal effects of radiotherapy (RT) allowing for use of lower doses of radiation to achieve equivalent cancer control, while minimizing adverse effects to normal tissues. Given their limited toxicity and ability to easily integrate into the diet, compounds occurring naturally in the diet make ideal potential radio-sensitizing agents. In this study, we have examined whether capsaicin, the active compound in chilli peppers, can modulate the response to RT in preclinical models of prostate cancer (PCa).

METHODS
The effects of RT (1–8 Gy) and/or capsaicin (1–10 µM) on colony formation rates in human PCa cells were assessed using clonogenic assays. Mechanistic studies were performed by Western Blot, immunocytochemistry, and flow cytometry. Athymic mice (n = 40) were inoculated with human LNCaP cells. Once tumors reached 100 mm3, animals were randomized into four groups: control, capsaicin alone (5 mg/kg/d), RT alone (6 Gy), and capsaicin and RT.

RESULTS
Capsaicin reduced colony formation rates and radio-sensitized human PCa cells (Sensitizer enhancement ratio = 1.3) which corresponded to the suppression of NFκB, independent of TRP-V1 receptor. Cell cycle modulation occurred following RT and capsaicin treatment independently. In vivo, oral administration of capsaicin with RT resulted in a ‘greater than additive’ growth delay and reduction in the tumor growth rate greater than capsaicin (P < 0.001) or RT (P < 0.03) alone. Immunohistochemical analysis revealed a reduction in proliferation and NFκB expression, and increase in DNA damage.

DISCUSSION
Our findings suggest that capsaicin acts as a radio-sensitzing agent for PCa through the inhibition of NFκB signalling.

Est-il contre-productif de vouloir trop bien faire?

16/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Vitamin C and E supplementation alters protein signalling after a strength training session, but not muscle growth during 10 weeks of training
G. Paulsen             December 15, 2014 The Journal of Physiology, 592, 5391-5408.

Although antioxidant supplements are generally believed to give health benefits, recent experiments show that they may adversely affect adaptations to endurance exercise.

This study is the first to investigate the effects of high dosages of vitamins C and E on the cellular and physiological adaptations to strength training in humans.

Here we report that vitamin C and E supplementation interfered with exercise‐induced signalling in muscle cells after a session of strength training, by reducing the phosphorylation of p70S6 kinase and mitogen‐activated protein kinases p38 and ERK1/2.

The vitamin C and E supplement did not significantly blunt muscle hypertrophy during 10 weeks of training; however, some measurements of muscle strength revealed lower increases in the supplemented group than the placebo group.

Even though the cellular events are not clearly reflected in physiological and performance measurements, this study implies that redox signalling is important for inducing skeletal muscle adaptations to strength training and that vitamin C and E supplements in high dosages should be avoided by healthy, young individuals engaged in strength training.


This study investigated the effects of vitamin C and E supplementation on acute responses and adaptations to strength training. Thirty‐two recreationally strength‐trained men and women were randomly allocated to receive a vitamin C and E supplement (1000 mg day−1 and 235 mg day−1, respectively), or a placebo, for 10 weeks. During this period the participants’ training involved heavy‐load resistance exercise four times per week. Muscle biopsies from m. vastus lateralis were collected, and 1 repetition maximum (1RM) and maximal isometric voluntary contraction force, body composition (dual‐energy X‐ray absorptiometry), and muscle cross‐sectional area (magnetic resonance imaging) were measured before and after the intervention. Furthermore, the cellular responses to a single exercise session were assessed midway in the training period by measurements of muscle protein fractional synthetic rate and phosphorylation of several hypertrophic signalling proteins. Muscle biopsies were obtained from m. vastus lateralis twice before, and 100 and 150 min after, the exercise session (4 × 8RM, leg press and knee‐extension). The supplementation did not affect the increase in muscle mass or the acute change in protein synthesis, but it hampered certain strength increases (biceps curl). Moreover, increased phosphorylation of p38 mitogen‐activated protein kinase, Extracellular signal‐regulated protein kinases 1 and 2 and p70S6 kinase after the exercise session was blunted by vitamin C and E supplementation. The total ubiquitination levels after the exercise session, however, were lower with vitamin C and E than placebo. We concluded that vitamin C and E supplementation interfered with the acute cellular response to heavy‐load resistance exercise and demonstrated tentative long‐term negative effects on adaptation to strength training.

Est-il contre-productif de vouloir trop bien faire?

16/12/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Vitamin C and E supplementation alters protein signalling after a strength training session, but not muscle growth during 10 weeks of training
G. Paulsen             December 15, 2014 The Journal of Physiology, 592, 5391-5408.

Although antioxidant supplements are generally believed to give health benefits, recent experiments show that they may adversely affect adaptations to endurance exercise.

This study is the first to investigate the effects of high dosages of vitamins C and E on the cellular and physiological adaptations to strength training in humans.

Here we report that vitamin C and E supplementation interfered with exercise‐induced signalling in muscle cells after a session of strength training, by reducing the phosphorylation of p70S6 kinase and mitogen‐activated protein kinases p38 and ERK1/2.

The vitamin C and E supplement did not significantly blunt muscle hypertrophy during 10 weeks of training; however, some measurements of muscle strength revealed lower increases in the supplemented group than the placebo group.

Even though the cellular events are not clearly reflected in physiological and performance measurements, this study implies that redox signalling is important for inducing skeletal muscle adaptations to strength training and that vitamin C and E supplements in high dosages should be avoided by healthy, young individuals engaged in strength training.


This study investigated the effects of vitamin C and E supplementation on acute responses and adaptations to strength training. Thirty‐two recreationally strength‐trained men and women were randomly allocated to receive a vitamin C and E supplement (1000 mg day−1 and 235 mg day−1, respectively), or a placebo, for 10 weeks. During this period the participants’ training involved heavy‐load resistance exercise four times per week. Muscle biopsies from m. vastus lateralis were collected, and 1 repetition maximum (1RM) and maximal isometric voluntary contraction force, body composition (dual‐energy X‐ray absorptiometry), and muscle cross‐sectional area (magnetic resonance imaging) were measured before and after the intervention. Furthermore, the cellular responses to a single exercise session were assessed midway in the training period by measurements of muscle protein fractional synthetic rate and phosphorylation of several hypertrophic signalling proteins. Muscle biopsies were obtained from m. vastus lateralis twice before, and 100 and 150 min after, the exercise session (4 × 8RM, leg press and knee‐extension). The supplementation did not affect the increase in muscle mass or the acute change in protein synthesis, but it hampered certain strength increases (biceps curl). Moreover, increased phosphorylation of p38 mitogen‐activated protein kinase, Extracellular signal‐regulated protein kinases 1 and 2 and p70S6 kinase after the exercise session was blunted by vitamin C and E supplementation. The total ubiquitination levels after the exercise session, however, were lower with vitamin C and E than placebo. We concluded that vitamin C and E supplementation interfered with the acute cellular response to heavy‐load resistance exercise and demonstrated tentative long‐term negative effects on adaptation to strength training.

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