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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.

Cryothérapie Corps Entier Vs eau froide pour la récupération?

10/01/2018 | Etudes cardio et Echauffement et blessures

 

Recovery following a marathon: a comparison of cold water immersion, whole body cryotherapy and a placebo control
Laura J. Wilson     European Journal of Applied Physiology January 2018, Volume 118, Issue 1, pp 153–163 | Cite as

Purpose
Cryotherapy is an increasingly popular recovery strategy used in an attempt to attenuate the negative impact of strenuous physical activity on subsequent exercise. Therefore, this study aimed to assess the effects of whole body cryotherapy (WBC) and cold water immersion (CWI) on markers of recovery following a marathon.

Methods
Thirty-one endurance trained males completed a marathon. Participants were randomly assigned to a CWI, WBC or placebo group. Perceptions of muscle soreness, training stress and markers of muscle function were recorded before the marathon and at 24 and 48 h post exercise. Blood samples were taken at baseline, post intervention and 24 and 48 h post intervention to assess inflammation and muscle damage.

Results
WBC had a harmful effect on muscle function compared to CWI post marathon. WBC positively influenced perceptions of training stress compared to CWI. With the exception of C-reactive protein (CRP) at 24 and 48 h, neither cryotherapy intervention positively influenced blood borne markers of inflammation or structural damage compared to placebo.

Conclusion
The findings show WBC has a negative impact on muscle function, perceptions of soreness and a number of blood parameters compared to CWI, contradicting the suggestion that WBC may be a superior recovery strategy. Further, cryotherapy is no more effective than a placebo intervention at improving functional recovery or perceptions of training stress following a marathon. These findings lend further evidence to suggest that treatment belief and the placebo effect may be largely responsible for the beneficial effects of cryotherapy on recovery following a marathon.

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.

Impact nerveux des corticoïdes?

28/12/2017 | Etudes sur les hormones

 

Neural Correlates to the Increase in Maximal Force after Dexamethasone Administration
Baudry, Stéphane             Medicine & Science in Sports & Exercise. ., Post Acceptance: September 19, 2017

Purpose This study investigated the effects of short-term glucocorticoid administration on voluntary activation and intracortical inhibitory and facilitatory circuits.

Methods Seventeen healthy men participated in a pseudo randomized double-blind study to receive either dexamethasone (8 mg·d-1, n = 9 subjects) or placebo (n = 8 subjects) for 7 days. The ankle dorsiflexion torque, corresponding electromyography (EMG) of the tibialis anterior, and voluntary activation assessed by the interpolated twitch method using transcranial magnetic stimulation (TMS) were measured during a maximal voluntary contraction (MVC). Short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) were assessed at rest and during submaximal contraction (50% MVC torque) by paired-pulse TMS with the conditioning stimulus set at 0.8x of motor threshold (0.8x MT) and delivered 2 ms (SICI) and 13 ms (ICF) prior to the test stimulus (1.2x MT).

Results The MVC torque (+14%), tibialis anterior EMG (+31%) and voluntary activation (+3%) increased after glucocorticoid treatment (p<0.05). The increase in voluntary activation was associated with the gain in MVC torque (r2 = 0.56; p = 0.032). The level of SICI and the duration of the EMG silent period that followed the test TMS decreased (-18.6% and -13.5%, respectively) during the 50% MVC after treatment (p<0.05) while no significant change was observed for ICF. Neither SICI nor ICF changed after treatment when assessed at rest.

Conclusion Short-term dexamethasone treatment induced specific decrease in the excitability of intracortical inhibitory circuits that likely contributed to the increase in the voluntary activation and associated MVC torque.

Faut-il prendre sa taurine avant la musculation?

28/12/2017 | Etudes Compléments alimentaires

 

The Effect of Acute Taurine Ingestion on Human Maximal Voluntary Muscle Contraction
Lim, Zi Xiang       Medicine & Science in Sports & Exercise. ., Post Acceptance: September 22, 2017

Purpose To examine the effect of taurine ingestion on maximal voluntary muscle torque and power in trained male athletes with different caffeine habits.

Methods Fourteen male athletes aged 21.8 ± 2.5 years were separated into caffeine and non-caffeine consumers to control for the effect of caffeine withdrawal on muscle function. On separate occasions, participants performed four isokinetic or three maximal isometric knee extensions with and without taurine (40 mg/kg body mass) following a double blind, counterbalanced design. Muscle contractile performances were compared between the first sets as well as between the sets where these variables scored best.

Results In response to isokinetic contraction, taurine treatment in the non-caffeine consumers resulted in a significant fall in first (-16.1%; p=0.013) and best peak torque (-5.0%; p=0.016) as well as in first (-17.7%; p=0.015) and best power output (-8.0%; p=0.008). In the caffeine consumers deprived of caffeine, taurine intake improved best power (5.2%; p=0.045). With respect to the isometric variables, there was a significant decrease in the first (-5.1%; p=0.002) and best peak torque (-4.3%; p=0.032) in the non-caffeine group, but no effect in the group of caffeine consumers deprived of caffeine. Taurine ingestion increased blood taurine levels, but had no effect on plasma amino acid levels.

Conclusion Taurine ingestion is detrimental to maximal voluntary muscle power and both maximal isokinetic and isometric peak torque in non-caffeine consumers, whereas taurine ingestion in caffeine-deprived caffeine consumers improves maximal voluntary muscle power but has not effect on other aspects of contractile performance.

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.

Effet contra-latéral du foam roller

23/12/2017 | Echauffement et blessures

 

Does Foam Rolling Increase Pressure Pain Threshold Of Ipsilateral Lower Extremity Antagonist And Contralateral Muscles?
Scott W. Cheatham   Medicine & Science in Sports & Exercise. 49(5S):1066, May 2017.

Sports medicine professionals often prescribe foam rolling as an intervention to treat myofascial restrictions. Of particular interest, is the effect foam rolling has on the ipsilateral antagonist muscle and contralateral muscles. Recent research has observed ROM changes in these muscles after a foam rolling intervention. To date, no studies have examined how foam rolling effects the pressure pain threshold (PPT) levels of the ipsilateral antagonist and contralateral muscles. PURPOSE: To examine the acute effects of a foam rolling intervention on ipsilateral antagonist and contralateral muscle group PPT levels. METHODS: Twenty-one healthy participants (mean age 27.52± 8.9 years) (M=13, F=8) were recruited for this study and signed an IRB consent. Participants underwent pretest and immediate posttest PPT measures after a 2-minute video-guided foam roll intervention to the left quadriceps. PPTs were measured using a digital algometer to the ipsilateral left hamstrings and right quadriceps. Pretest and posttest measures were calculated using the paired t-test. Statistical significance was considered p< 0.05 using a two-tailed test. RESULTS: A significant difference was found between pretest to posttest measures for the ipsilateral hamstrings (t (20) = -6.2, p<0.001) and contralateral quadriceps (t (20) = -9.1, p<0.001) suggesting an increase in PPT.

CONCLUSIONS: These finding suggest that foam rolling of the quadriceps musculature may have an acute effect on the PPT of the ipsilateral hamstrings and contralateral quadriceps muscles. Individual may feel less discomfort due to a higher PPT. The ipsilateral decrease in hamstring PPT may have occurred through reciprocal inhibition and agonist pain perception from rolling on the left quadriceps. The cross-over effect of decreased right quadriceps PPT may have been from a more global neurophysiological response. Clinicians must consider these results to be exploratory and future investigations examining this intervention on PPT is warranted.

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