Etudes Musculation : page 2.4

Le mystère des courbatures…

26/12/2017 | Etudes Musculation

 

Muscle damage protective effect by two maximal isometric contractions on maximal eccentric exercise of the elbow flexors of the contralateral arm

Trevor C. Chen   Scandinavian Journal of Medicine & Science in Sports 23 December 2017

Muscle damage after 30 maximal eccentric contractions of the elbow flexors (30MVEC) is reduced when the same exercise is performed by the opposite arm, and when two maximal voluntary isometric contractions at a long muscle length (2MVIC) are performed prior to 30MVEC by the same arm. This study investigated the hypothesis that 2MVIC would attenuate muscle damage after 30MVEC performed by the opposite arm. Untrained young (20-25 y) men were placed into one of four experimental groups that performed 2MVIC at 1 (1d), 2 (2d), 4 (4d) or 7 days (7d) before 30 MVEC by the opposite arm, or one control group that performed 30MVEC only (n=13/group). Changes in indirect muscle damage markers after 30MVEC were compared among the groups by mixed-design two-way ANOVA. Maximal voluntary concentric contraction torque, range of motion, plasma creatine kinase activity and muscle soreness did not change significantly after 2MVIC. Changes in these variables after 30MVEC were smaller (p<0.05) for 1d (e.g., peak soreness: 45 ± 21 mm) and 2d groups (46 ± 20 mm) than control group (66 ± 18 mm), without significant differences between 1d and 2d groups. No significant differences in the changes were found among 4d, 7d and control groups, except for soreness showing smaller (P<0.05) increases for 4d group (54 ± 19 mm) than 7d (62 ± 17 mm) and control groups. These results supported the hypothesis, and showed that muscle damage induced by 30MVEC was reduced by 2MVIC performed 1-2 days prior to 30MVIC by the contralateral arm.

Les machines, plus efficaces que les poids, chez les débutantes

23/12/2017 | Etudes Musculation

 

Cela confirme ce que nous expliquions dans notre livre de musculation pour les femmes
https://www.amazon.fr/m%C3%A9thode-Delavier-musculation-pour-femme/dp/2711424731/ref=pd_sim_14_12?_encoding=UTF8&psc=1&refRID=099HB7JJY53382JT60M6


INFLUENCE OF BODY BUILD AND TRAINING MODALITY ON STRENGTH GAIN FOLLOWING
RESISTANCE TRAINING IN COLLEGE WOMEN
J. MAYHEW         Journal of Strength and Conditioning Research   VOLUME 31 | SUPPLEMENT 1 | 2017 | S129

Previous investigation has noted that neither body build nor
initial strength level appear to influence upper-body strength
gains resulting from a short-term resistance training (RT)
program in young men. Such information is lacking in young
women. With increasing interest of women in RT, it would be
beneficial to determine if the same outcome as noted in men
was operating in women.

Purpose: To determine the influence
of body build on changes in fat-free mass (FFM) and upperbody
strength resulting from RT in college women. Methods:
College women (n = 496) self-selected to train with free
weights (FW, n = 279) or machine weights (SVP, n = 217)
during 12 weeks of periodized RT. Fat mass (FM) and FFM,
determined from %fat (gender-specific skinfold equation) and
modality-specific 1RM were determined prior to RT. Women
were distributed according to body build and divided in thirds
(slender = SL, n = 164; average = AV, n = 168; solid = SO, n
= 164) based on the regression of FFM/Ht2 on FM/Ht2.

Results: RT groups were not significantly different initially on
any demographic variable. All 3 body build groups were significantly
different (p , 0.001) in body mass, FM, FFM, FFM/Ht,
and FM/Ht). The SVP group had a significantly greater initial
1RM (39.8 6 7.3 kg) than the FW group (33.7 6 7.1 kg). SL
(37.9 6 8.4 kg) and AV (36.4 6 7.6 kg) body types had
a greater initial 1RM than SO (34.8 6 7.1 kg). Following training,
the change in FFM was not significantly different for training
modality body type. Following RT, the SVP group made
significantly greater gains in 1RM (6.9 6 4.6 kg) than the
FW group (5.9 6 5.3 kg). However, there were no significant
difference (p = 0.78) among body build groups for gain in
absolute strength (SL = 5.9 6 5.3, AV = 6.1 6 5.3, SO =
5.9 6 4.1 kg).

Conclusions: Young women appear to make
slightly better muscle strength gains using machine weights
compared to FW.
However, body type does not appear to
influence training potential to gain strength from RT. Practical
Applications: When beginning RT, young women might consider
utilizing machine weights initially before switching to FW.

Chaleur ou froid pour optimiser l’anabolisme?

22/11/2017 | Echauffement et blessures et Etudes Musculation

 

Plus d’anabolisme, moins de catabolisme avec…

Impact of local heating and cooling on skeletal muscle transcriptional response related to myogenesis and proteolysis
Roksana B. Zak European Journal of Applied Physiology October 2017

Purpose

To determine the impact of local muscle heating and cooling on myogenic and proteolytic gene responses following resistance exercise.

Methods

Recreationally trained males (n = 12), age 25.3 ± 1.5, % body fat 13.6 ± 1.92, completed four sets of 8–12 repetitions of unilateral leg press and leg extension while heating one leg, and cooling the other. Muscle biopsies were taken from the vastus lateralis of each leg pre and 4 h post exercise.

Results

MyoD, FOXO1, and MuRF1 mRNA increased with exercise regardless of temperature (p < 0.05). Myostatin, MYF5, and atrogin-1 mRNA decreased with exercise regardless of temperature (p < 0.05). Myogenin, MRF4, and CASP3 mRNA were higher in the hot condition, compared to the cold (p < 0.05). PAX7 mRNA was lower in the hot compared to cold condition (p = 0.041). FOXO3 mRNA was higher in the cold compared to hot condition (p = 0.037). AKT1 and AKT2 were unaffected by either exercise or temperature. Femoral artery blood flow volume was higher in the hot (375.2 ± 41.2 ml min− 1), compared to the cold condition (263.5 ± 23.9 ml min− 1), p = 0.01. Tissue oxygen saturation was higher in the hot (71.7 ± 4.8%) than cold condition (55.3 ± 5.0%).

Conclusion

These results suggest an impaired muscle growth response with local cold application compared to local heat application.

Retour de la théorie de l’hyperplasie comme mode de croissance

18/08/2017 | Etudes Musculation

 

Differential requirement for satellite cells during overload-induced muscle hypertrophy in growing versus mature mice
Kevin A. Murach   Skelet Muscle. 2017; 7: 14.

Pax7+ satellite cells are required for skeletal muscle fiber growth during post-natal development in mice. Satellite cell-mediated myonuclear accretion also appears to persist into early adulthood. Given the important role of satellite cells during muscle development, we hypothesized that the necessity of satellite cells for adaptation to an imposed hypertrophic stimulus depends on maturational age.

Methods

Pax7CreER-R26RDTA mice were treated for 5 days with vehicle (satellite cell-replete, SC+) or tamoxifen (satellite cell-depleted, SC-) at 2 months (young) and 4 months (mature) of age. Following a 2-week washout, mice were subjected to sham surgery or 10 day synergist ablation overload of the plantaris (n = 6–9 per group). The surgical approach minimized regeneration, de novo fiber formation, and fiber splitting while promoting muscle fiber growth. Satellite cell density (Pax7+ cells/fiber), embryonic myosin heavy chain expression (eMyHC), and muscle fiber cross sectional area (CSA) were evaluated via immunohistochemistry. Myonuclei (myonuclei/100 mm) were counted on isolated single muscle fibers.

Results

Tamoxifen treatment depleted satellite cells by ≥90% and prevented myonuclear accretion with overload in young and mature mice (p < 0.05). Satellite cells did not recover in SC- mice after overload. Average muscle fiber CSA increased ~20% in young SC+ (p = 0.07), mature SC+ (p < 0.05), and mature SC- mice (p < 0.05). In contrast, muscle fiber hypertrophy was prevented in young SC- mice. Muscle fiber number increased only in mature mice after overload (p < 0.05), and eMyHC expression was variable, specifically in mature SC+ mice.

Conclusions

Reliance on satellite cells for overload-induced hypertrophy is dependent on maturational age, and global responses to overload differ in young versus mature mice.

Rôle de la sirtuine 1 dans l’hypertrophie

02/03/2017 | Etudes sur les hormones et Etudes Musculation et Etudes Anti-âge

 

SIRT1 may play a crucial role in overload induced hypertrophy of skeletal muscle
Erika Koltai J physiol 2017

Significant skeletal muscle mass guarantees functional wellbeing and is important for high level performance in many sports. Although the molecular mechanism for skeletal muscle hypertrophy has been well-studied, it still is not completely understood. In the present study, we used a functional overload model to induce plantaris muscle hypertrophy by surgically removing the soleus, and gastrocnemius muscles in rats. Two weeks of muscle ablation resulted in a 40% increase in muscle mass, which was associated with a significant increase in SIRT1 content and activity (P

< 0.001). SIRT1-regulated Akt, eNOS, GLUT4 levels were also induced in hypertrophied muscles, and SIRT1 levels correlated with muscle mass, paired box protein 7 (Pax7), proliferating cell nuclear antigen (PCNA) and nicotinamide phosphoribosyltransferase (Nampt) levels. Alternatively, decreased FOXO1 and increased K48 polyubiquitination also suggest that SIRT1 could also be involved in the catabolic process of hypertrophy. Furthermore, increased levels of K63 and muscle RING finger 2 (MuRF2) protein could also be important enhancers of muscle mass. We report here that the levels of miR1 and miR133a decrease in hypertrophy and negatively correlate with muscle mass, SIRT1, and Nampt levels. Our results reveal a strong agreement between SIRT1 levels and activity, SIRT1 regulated pathways, and overload-induced hypertrophy.

These findings, along with the well-known regulatory

roles that SIRT1 plays in modulating both anabolic and catabolic pathways, allow us to propose the hypothesis that SIRT1 may actually play a crucial causal role in overload induced hypertrophy of skeletal muscle. This hypothesis will now require rigorous direct and functional testing.

Effets de l’exercice sur les concentrations de l’irisine

21/10/2016 | Etudes cardio et Etudes Musculation et Etudes Perte de poids et Etudes Anti-âge

 

Effets de l’exercice sur les concentrations de l’irisine circulatoire chez les adultes sains : revue générale
Science & Sports Volume 31, Issue 5, October 2016, Pages 251–260       A.C. Rodrigues

Objectifs

L’irisine est une myokine induite par l’exercice, responsable de la régulation de la protéine découplante 1 (UCP-1) dans le tissu adipeux beige. Cette étude vise à faire le point sur les effets d’exercice aigus et chroniques sur les concentrations circulantes d’irisine chez les adultes sains.

Informations

Nous avons réalisé, à partir des bases de données Medline et ScienceDirect, une revue de la littérature parue entre janvier 2012 et mars 2016, en utilisant les termes d’indexation suivants : irisine, exercice aigu, exercice chronique et entraînement. Pour les besoins de l’analyse, les études ont été divisés en exercice aigu et exercice chronique. Seize articles répondaient aux critères d’inclusion/exclusion, huit études portant sur l’exercice aigu, quatre avec l’exercice chronique et quatre avec les deux. Parmi les études portant sur l’exercice aigu, deux seulement n’ont pas observé d’augmentation des concentrations sériques et plasmatiques d’irisine après la séance d’exercice. L’exercice en résistance et l’exercice à haute intensité augmentaient davantage l’irisine que l’exercice aérobie et que l’exercice à faible d’intensité. Une seule étude a révélé une augmentation des concentrations circulantes d’irisine après plusieurs semaines d’entraînement en comparaison aux concentrations mesurées avant entraînement. Une autre étude a observé une augmentation des concentrations circulantes d’irisine dans le groupe entraîné par rapport au groupe témoin.

Conclusion

L’exercice aigu augmente les concentrations circulantes d’irisine. L’exercice en résistance et l’exercice à haute intensité augmentent davantage l’irisine. Par contre, un entraînement prolongé de plusieurs semaines ne semble pas modifier les concentrations circulantes d’irisine.

De nouvelles cellules souches découvertes dans les muscles

30/09/2016 | Echauffement et blessures et Etudes Musculation

 

The first characterization of a novel (non-satellite cell) stem cell population in human skeletal muscle
J.P. Nederveen     Appl. Physiol. Nutr. Metab. Vol. 41, 2016 S376

Skeletal muscle stem cells (satellite cells; SC) represent the primary
cell population responsible for muscle regeneration/repair. SC content
and activation has been show to increase in response to muscle
damaging exercise. However, non-satellite cell progenitors, under experimental
conditions in animals, have been identified to form skeletal
muscle
when the SC population is compromised. PW1+ interstitial
cells (PIC) have also been shown, experimentally, to contribute to
muscle repair in animals. This cell population, however, has never
been identified in humans. We sought to examine the changes in both
PIC and SC content following a single bout of eccentric exercise. Ten
sedentary males (24±3 years of age; mean±SEM) were recruited. Percutaneous
muscle biopsies from the vastus lateralis muscle were taken
prior to a bout of eccentric exercise (Pre), and 6h, 24h, and 72 h
post-exercise. Muscle fiber size, SC and PIC content were determined
via immunofluorescent microscopy. mRNA expression was assessed
by RT-PCR. The number of SC increased from Pre (10.3±0.8 Pax7+cells/
100 fibers) to 72h post-exercise (12.3±2.0 Pax7+cells/100 fibers, p<0.05).
Similarly, PW1+ cells increased from Pre (2.1±0.6 PW1+ cells/100 fibers)
to 72h post-exercise (6.8±2.5 PW1+ cells/100 fibers, p<0.05). PW1 mRNA
expression was significantly (p<0.05) increased 1.9-fold from Pre to
72h post-exercise. Here, for the first time in humans, we identify a
population of cells which are located in the interstitium that respond
to eccentrically-induced muscle damage in a similar fashion to SC.

 

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