L’entraînement augmente la densité de récepteurs sur les muscles (évidemment, le régime ça ne va pas être bon).

Muscle hypertrophy and increased expression of leptin receptors in the musculus triceps brachii of the dominant arm in professional tennis players
Eur J Appl Physiol (2010) 108:749–758
Hugo Olmedillas · Joaquin Sanchis-Moysi

In rodents, endurance training increases leptin sensitivity in skeletal muscle; however, little is known about the effects of exercise on the leptin signalling system in human skeletal muscle. Thus, to determine whether chronic muscle loading increases leptin receptor (OBR170) protein expression, body composition dual-energy X-ray absorptiometry was assessed in nine professional male tennis players (24 § 4 years old) and muscle biopsies were obtained from the dominant (DTB) and non-dominant (NDTB) arm triceps brachii (TB), and also from the right vastus lateralis (VL). In each biopsy, the protein content of OB-R170, perilipin A, suppressor of cytokine signalling 3 (SOCS3), protein tyrosine phosphatase 1B (PTP1B) and signal transducer and activator of transcription 3 (STAT3) phosphorylation were determined by western blot. The DTB had 15% greater lean mass (P < 0.05) and 62% greater OB-R170 protein expression (P < 0.05) than the NDTB. SOCS3 and PTP1B protein expression was similar in both arms, while STAT3 phosphorylation was reduced in the NDTB. OB-R170 protein content was also higher in DTB than in VL (P < 0.05). In summary, this study shows that the functional isoform of the leptin receptor is up-regulated in the hypertrophied TB. The latter combined with the fact that both SOCS3 and PTP1B protein expression were unaltered is compatible with increased leptin sensitivity in this muscle. Our findings are also consistent with a role of leptin signalling in muscle hypertrophy in healthy humans. Introduction The ob/ob mouse, which does not produce leptin, and the db/db mouse, which lacks functional leptin receptors, have lower muscle mass than comparable wildtype lean mice (Madiehe et al. 2002; Trostler et al. 1979). Leptin administration to these mice promotes muscle hypertrophy (Madiehe et al. 2002; Sainz et al. 2009). Thus, muscle loading facilitates the expression of leptin receptors when accompanied by muscle hypertrophy, at least in muscles with a high proportion of type 2 fibres, as in the TB (Sanchís-Moysi et al. 2009). In summary, this study shows that TB hypertrophy is accompanied by up-regulation of the functional isoform of the leptin receptor. Given the cross-talk between IGF-I signalling and leptin signalling, this finding is compatible with a role for leptin signalling in muscle hypertrophy in healthy humans. Since hypertrophy occurred predominantly in type 2 fibres in the loaded TB and in type 1 fibres in the VL, our findings are consistent with a greater increase in OB-Rb content in hypertrophied type 2 muscle fibres.

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Réflexion silencieuse sur le repos intra-set :

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Cette étude montre le rôle essentiel du NO pour la masse musculaire, pour le force et contre la fatigue.

Mais quand est-ce que plus de NO devient trop de NO ?

Journal of Clinical Investigation

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Pour les matheux qui aiment se prendre la tête avec des conneries. Moi, je comprends rien. Ça tombe bien car je m’en fou de savoir combien tire la bande. Et si je veux le savoir, je monte sur une balance.

Elastic band prediction equations for combined free-weight and elastic band bench presses and squats.

Shoepe, TC, Ramirez, DA, and Almstedt, HC.J Strength Cond Res 24(1): 195-200, 2010

Elastic bands added to traditional free-weight techniques have become a part of suggested training routines in recent years. Because of the variable loading patterns of elastic bands (i.e., greater stretch produces greater resistance), it is necessary to quantify the exact loading patterns of bands to identify the volume and intensity of training. The purpose of this study was to determine the length vs. tension properties of multiple sizes of a set of commonly used elastic bands to quantify the resistance that would be applied to free-weight plus elastic bench presses (BP) and squats (SQ). Five elastic bands of varying thickness were affixed to an overhead support beam. Dumbbells of varying weights were progressively added to the free end while the linear deformation was recorded with each subsequent weight increment. The resistance was plotted as a factor of linear deformation, and best-fit nonlinear logarithmic regression equations were then matched to the data. For both the BP and SQ loading conditions and all band thicknesses tested, R2 values were greater than 0.9623. These data suggest that differences in load exist as a result of the thickness of the elastic band, attachment technique, and type of exercise being performed. Facilities should adopt their own form of loading quantification to match their unique set of circumstances when acquiring, researching, and implementing elastic band and free-weight exercises into the training programs.

TABLE 1. Regression equations and R2 values for all bands in the bench press and squat attachment configurations.

	Bench press		Squats
Color	Regression equation	R2	Regression equation	R2
Orange	y = 9.89 Ln(x) 2 37.89	R2 = 0.992	y = 6.44 Ln(x) 2 26.47	R2 = 0.962
Red	y = 20.75 Ln(x) 2 79.25	R2 = 0.992	y = 10.25 Ln(x) 2 44.52	R2 = 0.981
Black	y = 29.06 Ln(x) 2 111.86	R2 = 0.994	y = 17.08 Ln(x) 2 74.64	R2 = 0.983
Purple	y = 46.27 Ln(x) 2 178.80	R2 = 0.988	y = 23.79 Ln(x) 2 102.96	R2 = 0.989
Green	y = 109.81 Ln(x) 2 430.24	R2 = 0.991	y = 44.20 Ln(x) 2 191.82	R2 = 0.990

For example, it can be ascertained that a person with a BP reach of 175 cm (x) will incur a black band load of 38 kg (y) at the conclusion of the concentric phase (using the equation: y = 29.064 Ln(x) 2 111.860). For SQ, the black band resistance for a 145-cm band length (x) will be 10.5 kg (y), but this must be multiplied by 2 to account for each of the 2 bands on either end of the barbell during this type of exercise so that the total weight addition will be 21 kg at the conclusion of the concentric phase (using the equation: y = 17.078 Ln(x) 2 74.643). Large differences in the applied load exist as a result of 1) the thickness of the elastic band, 2) the attachment technique used, 3) the type of exercise being performed, 4) the individual anthropometrics of the individual lifter, and 5) ikely, the manufacturer of the elastic band.

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Les résultats auraient été encore meilleurs si les chercheurs arrêtaient la drogue. Ils ont fait faire un squat à 20 kg avec 100 kg de bande, le délire quoi !

Kinetic and kinematic differences between squats performed with and without elastic bands

Israetel, MA, McBridem, JM, Nuzzo, JL, Skinner, JW, and Dayne, AM.  J Strength Cond Res 24(1): 190-194, 2010

The purpose of this investigation was to compare kinetic and kinematic variables between squats performed with and without elastic bands equalized for total work. Ten recreationally weight trained males completed 1 set of 5 squats without (Wht) and with (Band) elastic bands as resistance. Squats were completed while standing on a force platform with bar displacement measured using 2 potentiometers. Electromyography (EMG) was obtained from the vastus lateralis. Average force-time, velocity-time, power-time, and EMG-time graphs were generated and statistically analyzed for mean differences in values between the 2 conditions during the eccentric and concentric phases. The Band condition resulted in significantly higher forces in comparison to the Wht condition during the first 25% of the eccentric phase and the last 10% of the concentric phase. However, the Wht condition resulted in significantly higher forces during the last 5% of the eccentric phase and the first 5% of the concentric phase in comparison to the Band condition. The Band condition resulted in significantly higher power and velocity values during the first portion of the eccentric phase and the latter portion of the concentric phase. Vastus lateralis muscle activity during the Band condition was significantly greater during the first portion of the eccentric phase and latter portion of the concentric phase as well. This investigation indicates that squats equalized for total work with and without elastic bands significantly alter the force-time, power-time, velocity-time, and EMG-time curves associated with the movements. Specifically, elastic bands seem to increase force, power, and muscle activity during the early portions of the eccentric phase and latter portions of the concentric phase.

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Plus l’intensité d’effort est grande, plus la réduction de l’envie de fumer est importante.

Effects of exercise on cravings to smoke: The role of exercise intensity and cortisol
Authors: Filippe Scerbo a;  Guy Faulkner b;  Adrian Taylor b; Scott Thomas a
Journal of Sports Sciences, Volume 28, Issue 1 January 2010 , pages 11 - 19

Research consistently demonstrates that a bout of moderate exercise alleviates cravings to smoke among abstaining smokers. The aims of this study were to examine whether doses of exercise (moderate or vigorous) reduced cravings differently, and whether reductions in cravings were associated with changes in cortisol concentration. Using a within-participant, crossover design, 18 participants conducted three 15-min treatment sessions on separate days: passive, walking (45-50% heart rate reserve), and running (80-85% heart rate reserve) conditions. Participants rated cravings at baseline, mid-treatment, and 0, 10, 20, and 30 min after each treatment. Salivary cortisol samples were collected at baseline, immediately after, and 30 min after each condition. Significant group time interactions were identified, demonstrating significant reductions in craving items after the walking and running conditions compared with the passive control. No significant differences in craving reductions were found between walking and running conditions. Post hoc comparisons found that running condition cravings to smoke scores were reduced for a longer duration post-treatment than post-walking condition scores. The decline in cortisol concentration was attenuated in the running group only. Vigorous exercise has a similar effect to moderate exercise in terms of the magnitude of craving reduction. However, performing bouts of moderate-intensity exercise may be a better recommendation for reducing cravings.

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Une nouvelle étude révèle que les injections de plaquettes ne seraient pas efficaces contre les tendinites :

Platelet-Rich Plasma Injection for Chronic Achilles Tendinopathy
A Randomized Controlled Trial
Robert J. de Vos, MD; Adam Weir, MBBS; Hans T. M. van Schie, DVM, PhD; Sita M. A. Bierma-Zeinstra, PhD; Jan A. N. Verhaar, MD, PhD; Harrie Weinans, PhD; Johannes L. Tol, MD, PhD
JAMA. 2010;303(2):144-149.

Context Tendon disorders comprise 30% to 50% of all activity-related injuries; chronic degenerative tendon disorders (tendinopathy) occur frequently and are difficult to treat. Tendon regeneration might be improved by injecting platelet-rich plasma (PRP), an increasingly used treatment for releasing growth factors into the degenerative tendon.

Objective To examine whether a PRP injection would improve outcome in chronic midportion Achilles tendinopathy.

Design, Setting, and Patients A stratified, block-randomized, double-blind, placebo-controlled trial at a single center (The Hague Medical Center, Leidschendam, the Netherlands) of 54 randomized patients aged 18 to 70 years with chronic tendinopathy 2 to 7 cm above the Achilles tendon insertion. The trial was conducted between August 28, 2008, and January 29, 2009, with follow-up until July 16, 2009.

Intervention Eccentric exercises (usual care) with either a PRP injection (PRP group) or saline injection (placebo group). Randomization was stratified by activity level.

Main Outcome Measures The validated Victorian Institute of Sports Assessment-Achilles (VISA-A) questionnaire, which evaluated pain score and activity level, was completed at baseline and 6, 12, and 24 weeks. The VISA-A score ranged from 0 to 100, with higher scores corresponding with less pain and increased activity. Treatment group effects were evaluated using general linear models on the basis of intention-to-treat.

Results After randomization into the PRP group (n = 27) or placebo group (n = 27), there was complete follow-up of all patients. The mean VISA-A score improved significantly after 24 weeks in the PRP group by 21.7 points (95% confidence interval [CI], 13.0-30.5) and in the placebo group by 20.5 points (95% CI, 11.6-29.4). The increase was not significantly different between both groups (adjusted between-group difference from baseline to 24 weeks, –0.9; 95% CI, –12.4 to 10.6). This CI did not include the predefined relevant difference of 12 points in favor of PRP treatment.

Conclusion Among patients with chronic Achilles tendinopathy who were treated with eccentric exercises, a PRP injection compared with a saline injection did not result in greater improvement in pain and activity.

En savoir + :  HealthNews

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