Etudes Musculation

Rôle de l’ IL-15/IL dans la synthèse des protéines après la muscu

17/01/2018 | Etudes sur les hormones et Etudes Musculation

 

Skeletal muscle IL-15/IL-15Rα and myofibrillar protein synthesis after resistance exercise
Scandinavian Journal of Medicine & Science Sports 28, Issue 1 January 2018 Pages 116–125
A. Pérez-López

In vitro and in vivo studies described the myokine IL-15 and its receptor IL-15Rα as anabolic/anti-atrophy agents, however, the protein expression of IL-15Rα has not been measured in human skeletal muscle and data regarding IL-15 expression remain inconclusive. The purpose of the study was to determine serum and skeletal muscle IL-15 and IL-15Rα responses to resistance exercise session and to analyze their association with myofibrillar protein synthesis (MPS).

Fourteen participants performed a bilateral leg resistance exercise composed of four sets of leg press and four sets of knee extension at 75% 1RM to task failure. Muscle biopsies were obtained at rest, 0, 4 and 24 hours post-exercise and blood samples at rest, mid-exercise, 0, 0.3, 1, 2, 4 and 24 hours post-exercise. Serum IL-15 was increased by ~5.3-fold immediately post-exercise, while serum IL-15Rα decreased ~75% over 1 hour post-exercise (P

<.001). Skeletal muscle IL-15Rα mRNA and protein expression were increased at 4 hours post-exercise by ~2-fold (P<.001) and ~1.3-fold above rest (P=.020), respectively. At 24 hours post-exercise, IL-15 (P=.003) and IL-15Rα mRNAs increased by ~2-fold (P=.002). Myofibrillar fractional synthetic rate between 0-4 hours was associated with IL-15Rα mRNA at rest (r=.662, P=.019), 4 hours (r=.612, P=.029), and 24 hours post-exercise (r=.627, P=.029). Finally, the

muscle IL-15Rα protein up-regulation was related to Leg press 1RM (r=.688, P=.003) and total weight lifted (r=.628, P=.009). In conclusion, IL-15/IL-15Rα signaling pathway is activated in skeletal muscle in response to a session of resistance exercise.

Effet de la respiration sur la pression intra-abdominale?

10/01/2018 | Etudes Musculation

 

Causal effect of intra-abdominal pressure on maximal voluntary isometric hip extension torque
European Journal of Applied Physiology January 2018, Volume 118, Issue 1, pp 93–99     Kota Tayashiki

Intra-abdominal pressure (IAP) has been recently shown to be associated specifically with maximal voluntary isometric contraction (MVC) torque of hip extension, although the causal relationship remains unclear. The present study aimed to elucidate whether IAP has a causal effect on hip extension MVC torque.

Methods
IAP during hip extension MVC was changed by controlling the lung volume (i.e., depth of inspiration). Twelve healthy males conducted MVCs of hip extension during breath-hold at full inspiration (inspiratory condition) or expiration (expiratory condition), or during normal breath-hold (normal condition). IAP during MVCs was measured a pressure transducer placed in the rectum.

Results
The IAP during hip extension MVC was significantly higher in inspiratory condition (132.0 ± 46.1 mmHg) than in the other two conditions and also higher in normal condition (104.6 ± 35.9 mmHg) than in expiratory condition (77.0 ± 39.1 mmHg). The hip extension MVC torque was significantly higher in inspiratory condition (297.7 ± 82.7 N m) than in expiratory condition (266.4 ± 84.5 N m). In each condition, the hip extension MVC torque correlated with IAP during the MVC task.

Conclusion
The current results suggest that IAP has a positive causal effect on hip extension MVC torque and that a sufficient increase in IAP directly leads to an enhancement of hip extension MVC torque.

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.

Page 1 sur 23 pages  1 2 3 >  Last »