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Endurance et hypertrophie font-ils bon ménage!

22/07/2014 | Etudes Musculation

 

Is muscle hypertrophy following resistance exercise regulated by truncated splice variants of PGC-1α?
Christopher G.R. Perry   Acta Physiologica 2014 Accepted Article (Accepted, unedited articles published online and citable. The final edited and typeset version of record will appear in future.)

In this issue, the investigation by Lundberg et al revisited a classic question of how muscle hypertrophy occurs following resistance exercise but not endurance exercise in human skeletal muscle. A recent study suggested the master transcriptional co-activator PGC-1α, known for regulating multiple transcriptional programs encoding mitochondrial and other metabolic proteins following endurance exercise, may also regulate muscle hypertrophy after resistance exercise through a truncated variant termed PGC-1α4 (Ruas et al 2012). Based on these findings, Lundberg and colleagues reasoned this model would predict a greater expression of this splice variant following resistance exercise vs endurance exercise in human skeletal muscle

A PGC-1α isoform induced by resistance training regulates skeletal muscle hypertrophy.

Cell. 2012 Dec 7;151(6):1319-31.  Ruas JL

PGC-1α is a transcriptional coactivator induced by exercise that gives muscle many of the best known adaptations to endurance-type exercise but has no effects on muscle strength or hypertrophy. We have identified a form of PGC-1α (PGC-1α4) that results from alternative promoter usage and splicing of the primary transcript. PGC-1α4 is highly expressed in exercised muscle but does not regulate most known PGC-1α targets such as the mitochondrial OXPHOS genes. Rather, it specifically induces IGF1 and represses myostatin, and expression of PGC-1α4 in vitro and in vivo induces robust skeletal muscle hypertrophy. Importantly, mice with skeletal muscle-specific transgenic expression of PGC-1α4 show increased muscle mass and strength and dramatic resistance to the muscle wasting of cancer cachexia. Expression of PGC-1α4 is preferentially induced in mouse and human muscle during resistance exercise. These studies identify a PGC-1α protein that regulates and coordinates factors involved in skeletal muscle hypertrophy.

Truncated splice variant PGC-1α4 is not associated with exercise-induced human muscle hypertrophy.
Lundberg TR           Acta Physiol (Oxf). 2014 May 6.

A truncated PGC-1α splice variant (PGC-1α4) has been implicated in the regulation of resistance exercise (RE)-induced muscle hypertrophy, and basal expression levels said to be augmented in response to concurrent aerobic (AE) and RE training.
AIM:
The current study investigated human muscle truncated and non-truncated PGC-1α transcripts in response to both acute and chronic RE, and with or without preceding AE (AE+RE).
METHODS:
Ten men performed 5 weeks of unilateral AE+RE and RE training. Before (untrained) and after (trained) this intervention, PGC-1α transcripts were assessed in vastus lateralis muscle biopsies obtained before and 3 h after acute RE, with or without preceding AE. Additionally, samples were collected 72 h after the last exercise bout of the training programme.
RESULTS:
The truncated splice variant increased (P < 0.05) its expression after acute exercise regardless of mode. However, the expression was greater (P < 0.05) after AE+RE than RE. Other PGC-1α transcripts showed similar response. Truncated transcripts originated from both the alternative and proximal promoter, and AE+RE increased PGC-1α expression from both promoter sites. RE induced transcripts from the alternative promoter only. PGC-1α expressions after acute exercise were comparable across isoforms in both untrained and trained muscle. Steady-state levels of isoforms were unchanged after 5-week training (P > 0.05). Exercise-induced expression of PGC-1α variants did not correlate with changes in muscle size or strength (P > 0.05).
CONCLUSION:
Our results do not support the view that truncated PGC-1α coordinates exercise-induced hypertrophy in human skeletal muscle. Rather, all PGC-1α isoforms appear to be regulated transiently in response to acute exercise and regardless of mode.

De la DMAA détectée dans une majorité de boosters d’importation

22/07/2014 |

 

Si ton booster à l’air trop fort pour être vrai, c’est probablement qu’il l’ait (trop fort mais pas vrai)

Rapid assessment of the illegal presence of 1,3-dimethylamylamine (DMAA) in sports nutrition and dietary supplements using 1 H NMR spectroscopy.
Monakhova YB   Drug Test Anal. 2014 Jun 9. doi: 10.1002/dta.1677. [Epub ahead of print]

1,3-Dimethylamylamine (DMAA) is a stimulant that can be found in pre-workout sports nutrition and dietary supplements. This practice is illegal because DMAA is not a safe food ingredient but rather an unapproved medicinal compound due to its pharmacological action. In order to determine the DMAA content in such products, a nuclear magnetic resonance (NMR) spectroscopic method was developed and validated (DMAA was quantified as DMAA-HCl). For quantification, the collective integral from two of the methyl groups of the molecule in the range δ 0.92-0.84 ppm was used. The method was linear over the examined range of 1-21 g/kg (R2  = 0.9937). The recoveries from spiked concentrations (0.1-6 g/kg) ranged between 85% and 105% (96% on average), with a relative standard deviation (RSD) of 1% for an authentic sample. The detection limit was 0.03 g/kg and the quantification limit was 0.08 g/kg (calculated for 75 mg sample weight). The actual DMAA-HCl content in the sample was quantified using calibration curves (external standardization) or 3,5-dinitrobenzoic acid as single-point internal standard. The developed NMR methodology was applied for the analysis of 16 products, from which 9 samples were found positive (the DMAA-HCl concentration varied between 3.1 g/kg and 415 g/kg). The method can be recommended for routine use in food testing, customs or doping control laboratories.

Les estrogènes du houblon ont un effet durable

22/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Pharmacokinetics of Prenylated Hop Phenols in Women Following Oral Administration of a Standardized Extract of Hops

Richard B. van Breemen         Molecular Nutrition & Food Research 2014 Accepted Article

Women seeking alternatives to hormone replacement therapy for menopausal symptoms often try botanical dietary supplements containing extracts of hops (Humulus lupulus L.). Hops contain 8-prenylnaringenin (8-PN), a potent phytoestrogen, the related flavanones 6-prenylnaringenin (6-PN) and isoxanthohumol (IX), and the prenylated chalcone xanthohumol (XN).

Methods and results

After chemically and biologically standardizing an extract of spent hops to these marker compounds, an escalating dose study was carried out in menopausal women to evaluate safety and pharmacokinetics. 8-PN, 6-PN, IX, and XN, sex hormones, and prothrombin time (PT/INR) were determined in blood samples and/or 24-h urine samples. There was no effect on sex hormones or blood clotting. The maximum serum concentrations of the prenylated phenols were dose-dependent and were reached from 2 to 7 h, indicating slow absorption. The marker compounds formed glucuronides that were found in serum and urine. Secondary peaks at 5 h in the serum concentration-time curves indicated enterohepatic recirculation. The serum concentration-time curves indicated demethylation of IX to form 8-PN and cyclization of XN to IX. Slow absorption and enterohepatic recirculation contributed to half-lives exceeding 20 h.

Conclusion

This human study indicated long half-lives of the estrogenic and proestrogenic prenylated phenols in hops but no acute toxicity.

Pourquoi la caféine n’agit pas chez tous les sportifs?

19/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 


Ergogenic Effects Of Caffeine Are Associated With Variation In The Adenosine A2a Receptor Gene (ADORA2A)

Bryan D. Loy                 MSSE May 2014 - Volume 46 - Supplement 1 5S p77

There are individual differences in the ergogenic effects of caffeine. Caffeine is an adenosine receptor antagonist. Variations in caffeine sensitivity have been linked to variations at
nucleotide position 1083 (rs5751876) in the ADORA2A gene which codes for the adenosine A2A receptor. Prior studies show that T allele homozygotes (TT) for the ADORA2A gene
consume less caffeine and show greater sensitivity to caffeine than C allele carriers (CC, CT).

PURPOSE: To determine if total work performed during a 10-min cycling time-trial differs as a function of ADORA2A genotype. TT carriers were hypothesized to show larger
increases in total work after consuming caffeine compared to CC/CT carriers.
METHODS: College students with high self-reported caffeine sensitivity and typical daily caffeine consumption (

<250 mg.day-1) were recruited. On Day 1, eligible volunteers
performed a cycling VO2peak test and gave saliva samples that were genotyped using competitive allele specific polymerase chain reaction analysis. On Day 2 and 3, cycle ergometry
was started 60-mins after consuming capsules containing 5 mg.kg-1 body weight caffeine or flour (placebo). Capsules were given double-blind, and the capsule order was
counterbalanced and randomized. Cycling consisted of a 5-min warm-up at 50 watts, 20-mins at the work rate eliciting 60% of VO2peak (~50% Wpeak) and a 10-min all-out time trial.
At the end of each minute during the trial participants made a choice to cycle during the next minute at either the same power, 10 W higher or 10 W lower. Complete data were obtained
from 7 TT and 19 CC/CT carriers. An independent samples t-test on difference scores tested the hypothesis.

RESULTS: The CC/CT and TT groups did not differ significantly on the Day 1 exercise test (Wpeak = 175±37 vs. 159±24; VO2peak = 34.3±8.2 vs. 31.1±4.2 ml.kg.min-1). The change
in total work was significantly different between genotypes, t(24) = -2.31, p = .03. Total work increased after caffeine consumption for the TT group (6.1 ± 4.5 kJ) but did not change for
the CC/CT group (-0.05 ± 6.5 kJ). The TT group had insignificantly larger decreases in perceived exertion (-1.0 vs. -0.6) and quadriceps pain (-1.2 vs. -0.5) in the caffeine trial.
CONCLUSION:

Caffeine increases total work in a 10-min cycling time trial among those with the ADORA2A TT genotype but not for C allele carriers.

Pas d’augmentation de la taille des tendons en muscu

19/07/2014 | Echauffement et blessures

 

Tendon Cross Sectional Area Is Not Associated With Muscle Volume
MSSE May 2014 - Volume 46 - Supplement 1 5S p47   Atsuki Fukutani


Tendon configuration is considered to be related to the tendon injury. Recently, some studies have reported that resistance training increases tendon cross sectional area (CSA), whereas
other studies did not show increase in tendon CSA. We hypothesized that tendon CSA would not be associated with muscle hypertrophy. If the tendon CSA increases by resistance
training, resistance-trained men would have larger tendon CSA than non-trained men.
PURPOSE: To compare tendon CSA between resistance-trained men and non-trained men.
METHODS: Sixteen of body builders or rugby players (21.3 ± 3.4 years, 1.73 ± 0.06 m, 83.6 ± 9.3 kg) were recruited as the Training group. In contrast, eleven of men who have no
experience of regular resistance training (20.3 ± 2.1 years, 1.70 ± 0.06 m, 54.0 ± 4.7 kg) were recruited as the Control group. Tendon CSA and muscle volume of triceps brachii (TB),
quadriceps femoris (QF) and triceps surae (TS) were calculated from magnetic resonance images. The cross sectional images of tendon were obtained with 5 mm interval, and mean
values of the tendon area calculated by three images were adopted as tendon CSA. In QF and TS, aforementioned tendon CSA was obtained in both proximal and distal portion of the
tendon. Muscle volume was obtained by the cross sectional images obtained with 20 mm interval, and was calculated by the integration of each muscle area through the proximal and
distal end of each muscle.
RESULTS: Muscle volume of three muscles were significantly larger in Training group than in Control group (TB: Training 626.0 ± 99.8 cm3, Control 243.1 ± 28.2 cm3, QF: Training
2525.5 ± 251.8 cm3, Control 1388.2 ± 141.6 cm3 , TS: Training 915.9 ± 145.4 cm3, Control 595.2 ± 95.1 cm3, p

< 0.001 in all muscles). On the other hand, a significant difference in
tendon CSA was found only in lower portion of TS tendon (Training 100.8 ± 14.6 mm2, Control 92.8 ± 9.6 mm2, p = 0.041).
CONCLUSION: These findings indicate that

tendon CSA is not associated with muscle volume, suggesting that long-term of resistance training does not increase tendon CSA.

L- Arginine , performances et hypoglycémie

19/07/2014 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Attention à la grosse incidence d’hypo

Over-the-counter L- Arginine Supplements To Improve Power In Track And Field
Robert J. Soderman     MSSE May 2014 - Volume 46 - Supplement 1 5S 165

PURPOSE: The purpose of this research project was to evaluate the benefits to human performance of an over-the-counter L-arginine supplement.
METHODS: Thirty-five collegiate track and field athletes (20 males and 15 females) performed two exercise trials consisting of a 30-second Wingate Anaerobic Power Cycle
Ergometer Test with a force setting based on 7.5% of body weight. Thirty minutes prior to each exercise trial the subjects consumed 5,000 mg of L-arginine (GNC) in eight ounces of
water (the dosage recommended by the manufacturer, L-arginine trial) or the equivalent volume of plain water (control trial).
RESULTS: Peak power (W/kg) was higher during L-arginine trials compared to control trials, these differences were statistically significant for all subjects (9.61+2.30, 9.10+1.82,
p=0.0303) and females (7.99+1.63, 7.66+1.59, p=0.0435), and approached statistical significance for males (10.82+1.97, 10.17+1.12, p=0.0811). Average power (W/kg) was higher
during L-arginine trials compared to control trials, but these differences approached statistically significance only for females (6.15+1.15, 5.74+1.01, p=0.0520). Males received an
average of 57.7 mg/kg of L-arginine while females received an average of 79.9 mg/kg of L-arginine. Fifteen subjects (42.9%), including 9 men (45.0%) and 6 women (40.0%), reported
feeling lightheaded, dizzy or nauseated following the L-arginine trials, while no subjects reported the muscle pumps or excited feelings advertised by the manufacturer following the
L-arginine trials.

CONCLUSIONS: The manufacturer!s recommended dosage of L-arginine improved peak power, which occurred during the first 10 seconds of the 30-second test, but did not improve
average power throughout the 30-second test.
The manufacturer!s recommended dosage of L-arginine may improve performance in rapid explosive movements, but those improvements
may not be sustained over longer periods of exercise. The manufacturers recommended dosage of L-arginine may be an effort to simplify the dosage and avoid calculations for the
consumer, but also may be balancing increasing the incidence of feeling lightheaded, dizzy or nauseated against additional improvements in performance that might be possible with a
larger dosage per kilogram.

Le sucre fait surtout prendre du bide

18/07/2014 | Etudes Perte de poids et Etudes Anti-âge

 

Sugar-Sweetened Beverage Consumption Is Associated with Abdominal Fat Partitioning in Healthy Adults
Jiantao Ma           J. Nutr. August 1, 2014 vol. 144 no. 8 1283-1290

Abdominal adiposity, particularly visceral adipose tissue (VAT), is independently linked to the pathogenesis of diabetes and cardiovascular diseases. Emerging evidence suggests that greater intake of sugar-sweetened beverages (SSBs) may be associated with abnormal fat accumulation in VAT. We examined whether habitual SSB consumption and diet soda intakes are differentially associated with deposition of body fat. We conducted a cross-sectional analysis using previously collected data in 2596 middle-aged adults (1306 men and 1290 women) from the Framingham Heart Study Offspring and Third Generation cohorts. VAT and abdominal subcutaneous adipose tissue (SAT) were measured using multidetector computed tomography. Habitual intake of SSBs and diet soda was assessed by a validated food frequency questionnaire.

We observed that SSB consumption was positively associated with VAT after adjustment for SAT and other potential confounders (P-trend < 0.001). We observed an inverse association between SSB consumption and SAT (P-trend = 0.04) that persisted after additional adjustment for VAT (P-trend < 0.001). Higher SSB consumption was positively associated with the VAT-to-SAT ratio (P-trend < 0.001). No significant association was found between diet soda consumption and either VAT or the VAT-to-SAT ratio, but diet soda was positively associated with SAT (P-trend < 0.001). Daily consumers of SSBs had a 10% higher absolute VAT volume and a 15% greater VAT-to-SAT ratio compared with nonconsumers, whereas consumption of diet soda was not associated with either volume or distribution of VAT.

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