3 séries de 30 secondes de sprint, caractérisé comme un effort bref et intense, se rapprochant dès lors de celui que l'on rencontre en musculation, chacune espacées de 20 minutes de repos, augmente la synthèse protéique musculaire et donc l'anabolisme musculaire.
Sprint exercise is characterized by repeated sessions of brief intermittent exercise at a high relative workload. However, little is known about the effect on mTOR pathway, an important link in regulation of muscle protein synthesis. An earlier training study showed a greater increase in muscle fibre cross sectional area in females than males. Therefore, we tested the hypothesis that activation of mTOR signalling is more pronounced in females than in males. Healthy males (n=9) and females (n=8) performed three bouts of 30-s sprint exercise with 20 min rest between.
Multiple blood samples were collected over time and muscle biopsy specimens were obtained at rest and 140 min after the last sprint.
Serum insulin increased by sprint exercise and more so in females than in males (gender (g) x time (t):P=0.04. In skeletal muscle, phosphorylation of Akt increased by 50% (t, P=0.001) and mTOR by 120% (t, P=0.002) independent of gender. The elevation in p70S6k phosphorylation was larger in females (g x t, P=0.03) and averaged 230% (P=0.006) as compared to 60% in males (P=0.04). Phosphorylation rpS6 increased by 660% over time independent of gender (t, P=0.003). Increase in phosphorylation of p70S6k was directly related to increase in serum insulin (r=0.68, P=0.004).
It is concluded that repeated 30-s all out bouts of sprint exercise separated by 20 min of rest, increases Akt/mTOR signalling in skeletal muscle. Secondly, signalling downstream of mTOR was stronger in females than in males after sprint exercise indicated by increased phosphorylation of p70S6k.
Centro de Estudos em Psicobiologia e Exercício, São Paulo, Brazil.
Sleep is essential for the cellular, organic and systemic functions of an organism, with its absence being potentially harmful to health and changing feeding behavior, glucose regulation, blood pressure, cognitive processes and some hormonal axes. Among the hormonal changes, there is an increase in cortisol (humans) and corticosterone (rats) secretion, and a reduction in testosterone and Insulin-like Growth Factor 1, favoring the establishment of a highly proteolytic environment. Consequently, we hypothesized that sleep debt decreases the activity of protein synthesis pathways and increases the activity of degradation pathways, favoring the loss of muscle mass and thus hindering muscle recovery after damage induced by exercise, injuries and certain conditions associated with muscle atrophy, such as sarcopenia and cachexia.
Copyright © 2011 Elsevier Ltd. All rights reserved.
Voir aussi : http://www.nutrimuscle.com/forum/viewtopic.php?t=5924
Une étude supplémentaire démontrant que l'entraînement pour l'hypertrophie est différent de l'entraînement pour la force.
Gain de force n’est donc pas égal à gain de muscle
Effects of Training Volume on Strength and Hypertrophy in Sedentary Young Japanese Men
Medicine & Science in Sports & Exercise: May 2011 - Volume 43 - Issue 5 - p 837
Our knowledge of the effects of training volume on upper-limb strength and hypertrophy in crossover designs is rather limited.
PURPOSE: The purpose of the present crossover study was to investigate the effects of training volume on muscular strength and hypertrophy of the elbow flexor muscles (biceps brachii and brachialis) in sedentary young Japanese men.
METHODS: Eight subjects (age, 25.0 ± 2.1 years; body weight, 64.2 ± 7.9 kg; height, 171.7 ± 5.1 cm) were recruited for this study. The subjects trained their elbow flexor muscles twice per week for 12 consecutive weeks using a seated dumbbell preacher curl. Subjects’ dominant and non-dominant arms were randomly assigned to training with 1 or 3 sets of 10 reps per set. Rest intervals between sets were 60 s. The one-repetition maximum (1RM) of each arm was measured every 4 weeks to evaluate strength gains. Magnetic resonance imaging (MRI) was used to determine changes in the cross-sectional area (CSA) of the biceps brachii and brachialis at the beginning and end of a 12-week training period.
RESULTS: Percentage gains in strength were 20.4% ± 21.6% in the 1-set arm and 31.7% ± 22.0% in the 3-set arm, although no significant differences were observed between the two protocols. However, the 3-set protocol significantly increased CSA (1 set, 8.0% ± 3.7%; 3 sets, 13.3% ± 3.6%; p
CONCLUSIONS: Training volume effects hypertrophy, whereas it showed a slight tendency (p <.076) to effect strength during 12 weeks of training in sedentary population.
If you stretch your muscles first before starting training, you will reduce the quality of your training session. You’ll develop less strength, researchers from Sao Paulo State University write in an article that will be published soon in the Journal of Strength and Conditioning Research.
The researchers did experiments with a couple of dozen women whose average age was 65.The women had started doing fitness training four months before they were subject to measurements, and trained three times a week. In the researchers’ exercise laboratory the women had to exercise their legs at maximal strength.
On some occasions the women started with a Standing Unilateral Quadriceps Stretch, shown in the illustration. In this exercise you stretch the muscles with slow movements and hold the stretch for a few seconds. After that the researchers tested the women’s maximal strength a couple of times after each other. On the other occasions the women exercised without stretching.
The women developed less maximal strength in their legs as a result of stretching. The table below shows this. MVC is the abbreviation for maximal voluntary contraction, a measurement of strength.
When the researchers attached electrodes to the women’s leg muscles, they noticed that the stretching did not reduce the electric activity in the muscles. Control = without stretching. The S-measurements were done at five-minute intervals. VM = vastus medialis, VL = vastus lateralis, BF = biceps femoris.
It’s not the first time that sports scientists have recorded the negative effect of stretching before training. One theory that has been put forward to explain the effect is that stretching reduces the connections between the muscles and the nervous system. This study shows that this is not the case. It seems that stretching changes something in the muscle itself.
"If static stretching is used to improve flexibility, then it is recommended that this stretching is not practiced just before the performance of activities that require high levels of muscular force", the researchers conclude. They emphasise that they studied a static form of stretching, and therefore can say nothing about other forms of stretching.
Strength athletes get more out of their gym time if they do periodised training. This means training for a couple of weeks for example with weights at which you can just manage 12 reps, and then doing a couple of weeks with weights you can manage 6 reps with. Say. But maybe it works even better to vary your weights each time – so one session with heavy weights followed by lighter weights the next, and so on.
Researchers at the Federal University of Sao Carlos reach this conclusion in the article they published recently in the Journal of Strength & Conditioning Research. The researchers did an experiment with 40 male students, all of whom had been training for at least one year.
The researchers divided the students into two groups. One group did classical linear periodised resistance training. [LP] These students first trained for a week using weights with which they could just manage 12 reps (12RM). The next week they trained at 10RM, the week after that at 8RM and the fourth week at 6RM. In the fifth week the students went back to 12RM.
The second group did daily undulating periodised resistance training. [DUP] This meant that they did something different in each training session. There was a system, but it’s easier to show this in the form of a schedule like the one below.
After 8 (T2) and 12 weeks (T3) the researchers measured their subjects’ progression. As you can see from the table below, both groups had made considerable progress.
And below we’ve drawn up a table summarising exactly how much progression the two groups had made in 12 weeks.
+ 15.0 kg
+ 28.4 kg
+ 65.5 kg
+ 93.0 kg
+ 6.1 kg
+ 10.0 kg
The DUP group showed much more progression than the LP group. Despite this, the variation was too great for the results to be statistically significant. Nevertheless the researchers conclude that it’s more effective to vary the weights you train with on a daily basis rather than weekly.
A few months ago we wrote about research on more effective ways of periodising. That study concluded that it’s better not to use a training scheme in which you gradually increase the weights each week, for example from 12RM to 10RM to 8RM and then 6RM. One week of light weights, then a week of heavy weights, followed by another week of intermediate weights worked better. A shock effect seems to help muscles grow faster.
Older women may be better off not doing cardio before starting on strength training. Cardio training reduces the number of reps that they can make when pumping iron, write Brazilian sports scientists working at the Rio de Janeiro Federal University in the Journal of Strength and Conditioning Research.
It’s not news that cardio training and power training can affect each other negatively. But there are very few studies with precise information on how cardio and power training get in each other’s way. If more information is available, maybe trainers will be able to put together even better programmes. The researchers have made a contribution with this study of two dozen older women, with an average age of 75. The women had all been training for at least five years in fitness centres, and had experience of both cardio and power training.
First the researchers got the women to run on a treadmill for twenty minutes. During one session they ran at sixty percent of their maximum heart rate (MHR), during the other they ran at eighty percent. The women were most tired after the more intensive cardio session. The figure below shows the tiredness score the women gave themselves.
After the cardio session the women had to train with weights. They did leg presses, leg extensions and leg curls. The researchers repeated the experiment a couple of times, but altered the order in which the test subjects did the exercises.
The researchers had set the effort load on the machines to a level at which the women were able to do ten reps. The graph below shows how many leg-curl reps the women were able to use. The solid grey bars represent the sets after the 60 percent MHR session, the bars with the diagonal strips represent the sets done after the 80 percent MHR session.
The more intensive the cardio session, the fewer reps. And the figures were pretty much the same for the other exercises. In addition, the women were more tired if their training started with an intensive cardio session.
The researchers suspect that older women at least, but perhaps also other groups, "should focus on one fitness component per exercise session". So it’s either cardio or strength training each session. Doing both during one training session is not optimal. "This would allow for a higher quantity—and, most likely, quality—of both modes of training without the negative effects of fatigue."
The muscle groups that you pay attention to first during your workout grow and gain relatively more strength than the other muscle groups. Sports scientists at the Universidade Federal do Rio de Janeirodiscovered this after doing an experiment on untrained men.
The Brazilians recruited 31 students from the Brazilian Navy Sergeants School and divided them into three groups: the LG-SM group, the SM-LG group and a control group.
The control group did nothing.
The LG-SM group did weight training for 12 weeks. During their workout the subjects started with the barbell bench press, then did lat-pulldowns, followed by the triceps extension machine and lastly a standing biceps curl with a straight bar. The subjects did four sets of each exercise. For the first four weeks of the experiment the subjects used weights at which they could perform 12-25 repetitions. Then they went up to weights at which they could manage 8-10 reps. Between sets they rested for two minutes.
The SM-LG group trained in exactly the same way. But they did the exercises in a different order. This lot first trained their biceps, then their triceps, then their lats and lastly their pecs.
The table below shows the gains in the strength for the different groups. It shows the changes in weight at which the subjects were able to make one rep. The figures marked with an asterisk show the increases that were statistically significant.
Bench press (1RM)
Lat pulldown (1RM)
Triceps extension (1RM)
Biceps curl (1RM)
The researchers also made scans of the subjects’ arms and used them to measure the increase in circumference of the biceps and triceps. There’s a scan at the top of the page.
"Based on the 1RM strength gains and effect size results of the current study, it appears exercises that are particularly important for the training goals of a program should be placed at the beginning of the training session, whether or not it is a large or a small muscle group exercise", the researchers conclude.
If your small muscle groups, like the shoulders, biceps and triceps, lag behind in their development, you may be able to remedy the situation by training them first and doing the big muscle groups afterwards. Brazilian sports scientists will publish an article on this soon in the Journal of Science and Medicine in Sport.
What exactly is the best way of going about power training? It's a question to which there will never be one answer. According to some approaches, the accent in a power training session should be placed on the large muscle groups, doing basic multi-joint exercises like bench presses, rows and squats. This heavy kind of training encourages the body to make anabolic hormones, which are what make your muscles grow. Sounds logical.
But the same applies to the other approach, which says that it just depends on which muscle group you want to develop. If you want bigger and stronger triceps, then train this group first. This way you’re still fresh and you can use heavier weights to train the muscle.
According to the Brazilian study, there’s more than an element of truth in the second approach. The researchers got two groups of eighteen-year-old students to train with weights. One group [G1] trained their large muscles first, and then the small groups: first the chest, then the back, then the shoulders and lastly the triceps and biceps. The second group [G2] did everything in the reverse order.
None of the students had previously done weight training. The figure below shows how the muscle power developed during the eight weeks. During the period of the study the test subjects trained three times a week, doing a workout that took in all of their upper body.
As the figure shows, the muscle group you train first shows the greatest strength progress. The amount of kilograms the test subjects lifted was the same for both groups.
And what applies to the development of strength also applies to increase in muscle mass. The table below shows progress in the chest and triceps for the two groups.
CG = control group, consisting of test subjects who did not train.
The message is clear. Train first the muscle groups you want to develop more.
In the gym there’s no exercise that trains only the muscle group you want to stimulate. Other groups are always involved. That’s why it’s not so easy to achieve directed growth of particular parts of the body. If you have strong shoulders and weak chest muscles, it’s pretty difficult to develop good pecs. Or is it not that difficult after all? Sports scientists at the University of South Carolina Upstate discovered a very simple method. Focus.
The researchers describe in their article, which was published recently in the Journal of Strength and Conditioning Research, how they attached electrodes to the teres major [a muscle in your upper back, that runs over your shoulder blade], the biceps and the latissimus dorsi to their subjects. They then got the 8 women, aged between 18 and 35, to do lat pull-downs.
The researchers recorded the electrical activity during two sets. The results are shown below.
The researchers then repeated the activity. First they got the women to perform one set. Then a trainer told the women that they should concentrate on getting the power for the movement out of their latissimus dorsi muscles. That was why they were doing lat pull-downs: to develop the broad upper back muscle.
The trainer explained to the women exactly where the lats are located, and touched the muscles in the women. Then the women performed another set. The figure below shows the electrical activity in the muscles.
Focussing your attention on a muscle group while performing a set increases the intensity with which your muscle takes part in the movement. Isolating muscles is a matter of good ol’ fashioned focus & concentration.
The researchers had the women train at 30 percent of their maximal strength. That’s too light. Bodybuilders train at 60-85 percent of their maximum. The researchers don’t know whether using focus to isolate a muscle group works as well at higher intensity.