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Etre bon en cardio enfant aide-t’il à prendre du muscle plus tard?

02/11/2018 | Etudes cardio et Etudes Musculation

 

Physiological adaptations to resistance training in rats selectively bred for low and high response to aerobic exercise training
Juha P. Ahtiainen         Experimental Physiology banner                 05 September 2018 https://doi.org/10.1113/EP087144

1 New Findings
What is the central question of this study?

Can phenotypic traits associated with low response to one mode of training be extrapolated to other exercise‐inducible phenotypes? The present study investigated whether rats that are low responders to endurance training are also low responders to resistance training.

What is the main finding and its importance?

After resistance training, rats that are high responders to aerobic exercise training improved more in maximal strength compared with low‐responder rats. However, the greater gain in strength in high‐responder rats was not accompanied by muscle hypertrophy, suggesting that the responses observed could be mainly neural in origin.

The purpose of this study was to determine whether rats selectively bred for low and high response to aerobic exercise training co‐segregate for differences in muscle adaptations to ladder‐climbing resistance training. Five high‐responder (HRT) and five low‐responder (LRT) rats completed the resistance training, while six HRT and six LRT rats served as sedentary control animals. Before and after the 6 week intervention, body composition was determined by dual energy X‐ray absorptiometry. Before tissue harvesting, the right triceps surae muscles were loaded by electrical stimulation. Muscle fibre cross‐sectional areas, nuclei per cell, phosphorylation status of selected signalling proteins of mTOR and Smad pathways, and muscle protein, DNA and RNA concentrations were determined for the right gastrocnemius muscle. The daily protein synthesis rate was determined by the deuterium oxide method from the left quadriceps femoris muscle. Tissue weights of fore‐ and hindlimb muscles were measured. In response to resistance training, maximal carrying capacity was greater in HRT (∼3.3 times body mass) than LRT (∼2.5 times body mass), indicating greater improvements of strength in HRT. However, muscle hypertrophy that could be related to greater strength gains in HRT was not observed. Furthermore, noteworthy changes within the experimental groups or differences between groups were not observed in the present measures. The lack of hypertrophic muscular adaptations despite considerable increases in muscular strength suggest that adaptations to the present ladder‐climbing training in HRT and LRT rats were largely induced by neural adaptations.

Utilisation de plaquettes contre les blessures

25/10/2018 | Etudes sur les hormones et Echauffement et blessures

 

Platelet releasate promotes skeletal myogenesis by increasing muscle stem cell commitment to differentiation and accelerates muscle regeneration following acute injury
David Scully Acta Physiol : 19 October 2018

Aim
The use of platelets as biomaterials has gained intense research interest. However, the mechanisms regarding platelet‐mediated skeletal myogenesis remain to be established. The aim of this study was to determine the role of platelet releasate in skeletal myogenesis and muscle stem cell fate in vitro and ex vivo respectively.

Methods
We analysed the effect of platelet releasate on proliferation and differentiation of C2C12 myoblasts by means of cell proliferation assays, immunohistochemistry, gene expression and cell bioenergetics. We expanded in vitro findings on single muscle fibres by determining the effect of platelet releasate on murine skeletal muscle stem cells using protein expression profiles for key myogenic regulatory factors.

Results
TRAP6 and collagen used for releasate preparation had a more pronounced effect on myoblast proliferation versus thrombin and sonicated platelets (P<0.05). In addition, platelet concentration positively correlated with myoblast proliferation. Platelet releasate increased myoblast and muscle stem cell proliferation in a dose‐dependent manner, which was mitigated by VEGFR and PDGFR inhibition. Inhibition of VEGFR and PDGFR ablated MyoD expression on proliferating muscle stem cells, compromising their commitment to differentiation in muscle fibres (P<0.001). Platelet releasate was detrimental for myoblast fusion and affected differentiation of myoblasts in a temporal manner. Most importantly we show that platelet releasate promotes skeletal myogenesis through the PDGF/VEGF‐Cyclin D1‐MyoD‐Scrib‐Myogenin axis and accelerates skeletal muscle regeneration after acute injury.

Conclusion
This study provides novel mechanistic insights on the role of platelet releasate in skeletal myogenesis and set the physiological basis for exploiting platelets as biomaterials in regenerative medicine.

Toutes les techniques d’entraînement se valent t-elles chez le débutant?

18/10/2018 | Etudes Musculation

 

Load and time under tension do not determine motor unit
activation during resistance exercise performed to volitional
failure in young, healthy men

R.W. Morton   Appl. Physiol. Nutr. Metab. Vol. 43, 2018       S83

We aimed to determine if performing resistance exercise (RE) to volitional
failure with heavier or lighter loads and shorter or longer times
under tension would result in similar motor unit activation.

Ten recreationally
active young men performed three sets of unilateral knee
extension exercise that varied in speed of contraction and load:
80%RM Regular (80R; 1 eccentric: 1 pause: 1 concentric), 80%RM Slow
(80S; 3:1:3), 30%RM Regular (30R; 1:1:1) and 30%RM Slow (30S; 3:1:3).
Peak EMG amplitude increased in every condition but was higher in
the heavy-load conditions during the first and last repetitions of each
set. The integrated EMG signal was higher in the light-load conditions.
Maximum voluntary force decreased between each set in every condition
with no difference between conditions. At rest, type II muscle
fibres had more glycogen than type I fibres with no difference between
type IIA and type IIX fibres. There were no differences in glycogen
depletion between conditions; however, glycogen depletion was
greater in type II than type I fibres and type IIA fibres depleted more
than type IIX fibres.

We conclude that performing RE to volitional
failure results in significant fatigue and motor unit activation that is
similar regardless of load or speed of contraction.

Efficacité des repos extrêmes entre les séries?

18/10/2018 | Etudes cardio et Echauffement et blessures et Etudes Musculation

 

Sprint exercise snacks: A novel approach to increase aerobic
fitness

G. Jackson         Appl. Physiol. Nutr. Metab. Vol. 43, 2018

Sprint interval training (SIT) is a time-efficient way to improve aerobic
fitness. The purpose of this study was to determine if performing
isolated sprints throughout the day with longer (>1 hour) rest periods
(i.e., “sprint snacks”) could comparably improve aerobic capacity. In a
randomized pilot trial, healthy, young, inactive participants performed
six weeks of training (3 d/wk) as either sprint snacks (SS; 3x20
sec with 1-4-hour rest, n=12) or SIT (3x20 sec with 3-minute rest within
a 10-minute session, n=16).

The primary outcome was peak oxygen
uptake (V˙ O2peak) assessed before and after training. Absolute
V˙ O2peak increased by 4% after SS and 6% after SIT (main effect of
time P = 0.004) with no difference between groups (group X time
interaction, P = 0.559). In SIT, exercise enjoyment increased from the
first training session (3.8 ± 1.4) to final training session (5.2 ± 1.2)
whereas enjoyment of SS did not change (4.8 ± 1.9 to 4.5 ± 1.4) (group X
time interaction, P = 0.01). Performing three all-out intensity “sprint
snacks” spread throughout the day can lead to similar aerobic adaptations
when compared to a time-efficient SIT protocol involving the
same number and length of sprints.
Future research should examine
whether sprint snacks can be translated into an effective real-world
intervention.

Le jus de cassis comme inhibiteur MAO?

10/10/2018 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

The pharmacodynamic profile of “Blackadder” blackcurrant juice effects upon the monoamine axis in humans: A randomised controlled trial
Anthony W. Watson       Nutritional Neuroscience         05 Oct 2018

Emerging evidence from human intervention trials indicates health benefits of consuming blackcurrant fruit, including improvements to cognitive performance, modulation of blood flow, regulation of blood glucose and inhibition of enzymes underpinning normal cognitive function. Of particular relevance is our previous demonstration of monoamine oxidase (MAO)-A and B inhibition after the consumption of a New Zealand “Blackadder” blackcurrant juice in humans.

The current study uses a double-blind, placebo-controlled, randomised cross- over design to assess the pharmacodynamics of the effects on platelet MAO-B inhibition and associated substrates, plasma prolactin levels and blood glucose levels after consumption of a single serve of “Blackadder” blackcurrant juice standardised to 500 mg polyphenols. Eight healthy male (20-–35 years) participants completed the trial. Measurements were obtained at baseline 15, 30, 45, 60, 100, 120, 150, 180, 240 mins and 24 h post dose.

A fast, absolute and reversible inhibition of blood platelet MAO-B (P 

< 0.001) and a significant but delayed reduction in plasma prolactin (P 

< 0.001) were observed following the consumption of “Blackadder” blackcurrant juice when compared to a placebo control. No interpretable changes in substrates of MAO or associated metabolites were seen.

These data provide a clear time course of the reversible inhibition of MAO-B after the single consumption of a of New Zealand “Blackadder” blackcurrant juice standardised at

500 mg of polyphenols and, therefore, provide a therapeutic window on which to base future nutritional interventions.

Liens Cordyceps sinensis et cancer?

02/10/2018 | Etudes Compléments alimentaires et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Cordyceps sinensis Promotes the Growth of Prostate Cancer Cells
Ming-wei Ma           Nutrition and Cancer   01 Oct 2018

Abstract
Background: This study aims to test whether Cordyceps sinensis (CS), the most expensive Asian nutrient supplement might stimulate growth of prostate cancer cells.

Methods: Impact of CS on growth of prostate cancer was determined in vivo and in vitro.

Results: Firstly, the serum testosterone level was significantly elevated in mice fed CS. Prostate glands were significantly enlarged (weight index 0.53 ± 0.04 mg/g vs. 0.31 ± 0.04 mg/g, P = 0.006). Furthermore, cell viability was increased twofold in the androgen-responsive prostate cancer cell line (VCaP) after CS treatment. This promoting effect disappeared after bicalutamide was added. In addition, serum prostate-specific antigen (PSA) in mice bearing VCaP xenografts was significantly elevated (0.66 ± 0.04 ng/ml vs. 0.26 ± 0.06 ng/ml, P 

< 0.001) after treatment with CS. Finally, VCaP tumors in mice treated with CS grew much faster (479.2 ± 78.74 mm3 vs. 283 ± 58.97 mm3, P = 0.074). However, the above promoting effects of CS were not observed in parallel studies using the PC-3 cell line which lacks AR expression.

Conclusions:

These results suggest that CS promotes growth of prostate cancer cells by increasing production of testosterone and stimulating the AR-dependent pathway. Additional studies are required to see whether CS is safely consumed by patients with prostate cancer.

Faut-il conserver sa whey au frigo?

26/09/2018 | Etudes Compléments alimentaires

 

Génération de rougeur via les réactions de Maillard d’isolat de protéine de lactosérum (WPI) et d’acide ascorbique (vitamine C) dans des poudres séchées par pulvérisation
Chao Zhong Songwen Tan Timothy LangrishJournal of Food Engineering

Points forts
• Les réactions de Maillard de WPI et d’acide ascorbique dans les poudres séchées par pulvérisation sont étudiées.
• Le changement de couleur et la génération de fluorescence sont observés après la réaction de Maillard.
• La température de stockage affecte de manière significative les réactions de Maillard.
• Les basses températures ou le faible stockage de l’oxygène peuvent réduire les effets des réactions de Maillard.

Des rougeurs évidentes ont été observées lors du stockage et du traitement des poudres d’acide WPI-ascorbique séchées par pulvérisation. La limite inférieure de détection par observation humaine est de 0,001 g / mL pour la concentration d’ acide ascorbique (rapport AA: WPI de 1: 100). La rougeur est liée à l’ adsorption de la lumière violette (380 nm) et de la lumière bleue / verte (500 nm). L’analyse par fluorescence suggère la formation de formylthéosylpyrroles et de poly (acides aminés) réticulés. L’analyse DSC montre que les pics d’acide ascorbique disparaissent sous forme de réaction de Maillard. La température de stockage s’est avérée affecter de manière significative les réactions de Maillard entre le WPI et l’acide ascorbique.

Les résultats montrent que les taux de réaction de Maillard entre WPI et acide ascorbique sont rapides dans les poudres séchées par pulvérisation, même à 20 ° C. Il est suggéré que les laits en poudre pour nourrissons / bébés formulés sur le marché nécessitent un stockage à basse température (4 ° C) ou à faible teneur en oxygène ( atmosphère N 2) afin de réduire les effets des réactions de Maillard (génération de rougeurs).

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