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.

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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

(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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Comme expliqué dans La méthode Delavier de musculation, volume 2 !

COMPARISON OF PERFORMANCE VARIABLES AND MUSCLE ACTIVITY DURING THE SQUAT AND BOX SQUAT
J. W. SKINNER, J. M. MCBRIDE, T. J. KIRBY,
P. C. SCHAFER, AND T. L. HAINES

PURPOSE:

The purpose of this investigation is to determine the difference in performance variables and muscle activity between a squat with or without (box squat) a stretch-shortening cycle or coupling phase. A box squat removes the coupling phase by requiring the lifter to lower the weight, sit on a box and then raise the weight. This may allow the lifter to focus on concentric phase muscle activity by removing the stretch-shortening cycle.

METHODS:

Eight resistance-trained males (Height: 179.61 6 13.43 cm; Body Mass: 107.65 6 29.79 kg; Age: 24.77 6 3.22 years; 1RM: 200.11 6 58.91 kg) with at least 3 years of experience performing the back squat with no prior injuries within the last year prior to participating in the study. Subjects were asked to perform two trials of a squat (S) and box squat (BS) at 60%, 70%, and 80% of their one their repetition maximum (1RM) in a randomized fashion. Each trial of the S and BS was performed with the subject standing on a force plate with a bar attached to two potentiometers. Squat performance was determined by calculating peak force (PF), peak power (PP), and peak velocity (PV). Muscle activity was monitored through electromyography (EMG) for all squats for the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF), and longissimus (L1) muscles.

RESULTS:

Muscle activity was significantly higher for BF during the concentric (0.15 6 0.067; 0.0289) and eccentric (0.03 6 0.007; 0.0262) phase of S when compared to BS at 60% of 1RM. Muscle activity was significantly higher for VL (0.472 6 0.158; 0.005) in the concentric phase of the S when compared to the BS at 70% of 1RM. Muscle activity was also higher at VL (0.313 6 0.084; 0.041) and L1 (0.167 6 0.090; 0.009) during the eccentric phase of the S compared to the BS at 80% of 1RM.

CONCLUSIONS:

Muscle activity was generally higher in the S with several significant differences noted in comparison to the BS. It does not appear that the BS, which removes the coupling phase, increases muscle activity in either the eccentric or concentric phase.

PRACTICAL APPLICATIONS:

The box squat does not appear to be a viable alternative to squatting due to a decrease in muscle activity, which would not optimize training adaptations.

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