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S’entraîner les cuisses pour renforcer les bras ?
Physiological elevation of endogenous hormones results in superior strength training adaptation
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY Bent R. Rønnestad, Håvard Nygaard and Truls Raastad
The purpose of this study was to determine the influence of transiently elevated endogenous hormone concentrations during exercise on strength training adaptations. Nine subjects performed four unilateral strength training session per week on the elbow flexors for 11 weeks. During two of the weekly sessions, leg exercises were performed to acutely increase the systemic anabolic hormone concentration immediately before the exercises for one of the elbow flexors (L + A). On the two other weekly training sessions, the contralateral elbow flexors were trained without prior leg exercises (A). By randomizing one arm of the subjects to serve as a control and the other as experimental, both conditions have the same nutritional and genetic environment. Serum testosterone and growth hormone was significantly increased during the L − A training session, while no hormonal changes occurred in the A session. Both A and L + A increased 1RM in biceps curl, peak power in elbow flexors at 30 and 60% of 1RM, and muscle volume of the elbow flexors (p < 0.05). However, only L + A achieved increase in CSA at the part of the arm flexors with largest cross sectional area (p < 0.001), while no changes occurred in A. L + A had superior relative improvement in 1RM biceps curl and favorable muscle adaptations in elbow flexors compared to A (p < 0.05). In conclusion, performing leg exercises prior to arm exercises, and thereby increasing the levels of serum testosterone and growth hormone, induced superior strength training adaptations compared to arm training without acute elevation of hormones.
En combien de temps le muscle commence à grossir en débutant la muscu ?
An examination of the time course of training-induced skeletal muscle hypertrophy
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY
Jason M. DeFreitas, Travis W. Beck, Matt S. Stock, Michael A. Dillon and Paul R. Kasishke
Skeletal muscle hypertrophy is typically considered to be a slow process. However, this is partly because the time course for hypertrophy has not been thoroughly examined. The purpose of this study was to use weekly testing to determine a precise time course of skeletal muscle hypertrophy during a resistance training program. Twenty-five healthy, sedentary men performed 8 weeks of high-intensity resistance training. Whole muscle cross-sectional area (CSA) of the dominant thigh was assessed using a peripheral quantitative computed tomography scanner during each week of training (W1–W8). Isometric maximum voluntary contractions (MVC) were also measured each week. After only two training sessions (W1), the mean thigh muscle CSA increased by 5.0 cm2 (3.46%; p
< 0.05) from the pre-testing (P1) and continued to increase with each testing session. It is possible that muscular edema may have influenced the early CSA results. To adjust for this possibility, with edema assumedly at its highest at W1, the next significant increase from W1 was at W3. W4 was the first significant increase of MVC over P1. Therefore,significant skeletal muscle hypertrophy likely occurred around weeks 3–4. Overall, from the pre-testing to W8, there was an increase of 13.9 cm2 (9.60%). These findings suggested that training-induced skeletal muscle hypertrophy may occur early in a training program.
L’ornithine augmente les performances
Effect of l-ornithine hydrochloride ingestion on intermittent maximal anaerobic cycle ergometer performance and fatigue recovery after exercise
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY Shinichi Demura, Koji Morishita, Takayoshi Yamada, Shunsuke Yamaji and Miho Komatsu
l-Ornithine plays an important role in ammonia metabolism via the urea cycle. This study aimed to examine the effect of l-ornithine hydrochloride ingestion on ammonia metabolism and performance after intermittent maximal anaerobic cycle ergometer exercise. Ten healthy young adults (age, 23.8 ± 3.9 year; height, 172.3 ± 5.5 cm; body mass, 67.7 ± 6.1 kg) with regular training experience ingested l-ornithine hydrochloride (0.1 g/kg, body mass) or placebo after 30 s of maximal cycling exercise. Five sets of the same maximal cycling exercise were conducted 60 min after ingestion, and maximal cycling exercise was conducted after a 15 min rest. The intensity of cycling exercise was based on each subject’s body mass (0.74 N kg−1). Work volume (watt), peak rpm (rpm) before and after intermittent maximal ergometer exercise and the following serum parameters were measured before ingestion, immediately after exercise and 15 min after exercise: ornithine, ammonia, urea, lactic acid and glutamate. Peak rpm was significantly greater with l-ornithine hydrochloride ingestion than with placebo ingestion. Serum ornithine level was significantly greater with l-ornithine hydrochloride ingestion than with placebo ingestion immediately and 15 min after intermittent maximal cycle ergometer exercise. In conclusion, although maximal anaerobic performance may be improved by l-ornithine hydrochloride ingestion before intermittent maximal anaerobic cycle ergometer exercise, the above may not depend on increase of ammonia metabolism with l-ornithine hydrochloride.
8 séries de squats, c’est mieux qu’une
Strength and neuromuscular adaptation following one, four, and eight sets of high intensity resistance exercise in trained males
EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY P. W. M. Marshall, M. McEwen and D. W. Robbins
The optimal volume of resistance exercise to prescribe for trained individuals is unclear. The purpose of this study was to randomly assign resistance trained individuals to 6-weeks of squat exercise, prescribed at 80% of a 1 repetition-maximum (1-RM), using either one, four, or eight sets of repetitions to failure performed twice per week. Participants then performed the same peaking program for 4-weeks. Squat 1-RM, quadriceps muscle activation, and contractile rate of force development (RFD) were measured before, during, and after the training program. 32 resistance-trained male participants completed the 10-week program. Squat 1-RM was significantly increased for all groups after 6 and 10-weeks of training (P
< 0.05). The 8-set group was significantly stronger than the 1-set group after 3-weeks of training (7.9% difference, P < 0.05), and remained stronger after 6 and 10-weeks of training(P < 0.05). Peak muscle activation did not change during the study. Early (30, 50 ms) and peak RFD was significantly decreased for all groups after 6 and 10-weeks of training (P < 0.05). Peak isometric force output did not change for any group. The results of this study support resistance exercise prescription in excess of 4-sets (i.e. 8-sets) for faster and greater strength gains as compared to 1-set training. Common neuromuscular changes are attributed to high intensity squats (80% 1-RM) combined with a repetition to failure prescription. This prescription may not be useful for sports application owing to decreased early and peak RFD. Individual responsiveness to 1-set of training should be evaluated in the first 3-weeks of training.
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