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BACKGROUND: The major thiol-disulfide couple of reduced glutathione (GSH) and oxidized glutathione is a key regulator of major transcriptional pathways regulating aseptic inflammation and recovery of skeletal muscle after aseptic injury. Antioxidant supplementation may hamper exercise-induced cellular adaptations. OBJECTIVE: The objective was to examine how thiol-based antioxidant supplementation affects skeletal muscle's performance and redox-sensitive signaling during the inflammatory and repair phases associated with exercise-induced microtrauma. DESIGN: In a double-blind, crossover design, 10 men received placebo or N-acetylcysteine (NAC; 20 mg · kg(-1) · d(-1)) after muscle-damaging exercise (300 eccentric contractions). In each trial, muscle performance was measured at baseline, after exercise, 2 h after exercise, and daily for 8 consecutive days. Muscle biopsy samples from vastus lateralis and blood samples were collected before exercise and 2 h, 2 d, and 8 d after exercise. RESULTS: NAC attenuated the elevation of inflammatory markers of muscle damage (creatine kinase activity, C-reactive protein, proinflammatory cytokines), nuclear factor κB phosphorylation, and the decrease in strength during the first 2 d of recovery. NAC also blunted the increase in phosphorylation of protein kinase B, mammalian target of rapamycin, p70 ribosomal S6 kinase, ribosomal protein S6, and mitogen activated protein kinase p38 at 2 and 8 d after exercise. NAC also abolished the increase in myogenic determination factor and reduced tumor necrosis factor-α 8 d after exercise. Performance was completely recovered only in the placebo group. CONCLUSION: Although thiol-based antioxidant supplementation enhances GSH availability in skeletal muscle, it disrupts the skeletal muscle inflammatory response and repair capability, potentially because of a blunted activation of redox-sensitive signaling pathways. This trial was registered at cl

Regular performance of resistance exercise induces an increase in skeletal muscle mass, however, the molecular mechanisms underlying this effect are not yet fully understood. The purpose of the present investigation was to examine acute changes in molecular signalling in response to resistance exercise involving different training volumes. Eight untrained male subjects carried out one, three and five sets of 6 repetition maximum (RM) in leg press exercise in a random order. Muscle biopsies were taken from the vastus lateralis both prior to and 30 min after each training session and the effect on protein signalling was studied. Phosphorylation of Akt was not altered significantly after any of the training protocols, whereas that of the mammalian target of rapamycin was enhanced to a similar extent by training at all three volumes. The phosphorylation of p70S6 kinase (p70(S6k)) was elevated threefold after 3 × 6 RM and sixfold after 5 × 6 RM, while the phosphorylation of S6 was increased 30- and 55-fold following the 3 × 6 RM and 5 × 6 RM exercises, respectively. Moreover, the level of the phosphorylated form of the gamma isoform of p38 MAPK was enhanced three to fourfold following each of the three protocols, whereas phosphorylation of ERK1/2 was unchanged 30 min following exercise. These findings indicate that when exercise is performed in a fasted state, the increase in phosphorylation of signalling molecules such as p70(S6k) and the S6 ribosomal protein in human muscle depends on the exercise volume.

The purpose of the present study was to investigate the possible relationship between a change in Thr(389) phosphorylation of p70S6 kinase (p70(S6k)) after a single resistance training session and an increase in skeletal muscle mass following short-term resistance training. Eight male subjects performed an initial resistance training session in leg press, six sets of 6RM with 2 min between sets. Muscle biopsies were obtained from the vastus lateralis before (T1) and 30 min after the initial training session (T2). Six of these subjects completed a 14-week resistance-training programme, three times per week (nine exercises, six sets, 6RM). A third muscle biopsy was obtained at the end of the 14-week training period (T3). One repetition maximum (1RM) squat, bench press and leg press strength as well as fat-free mass (FFM, with dual energy X-ray absorptiometry) were determined at T1 and T3. The results show that the increase in Thr(389) phosphorylation of p70(S6k) after the initial training session was closely correlated with the percentage increase in whole body FFM (r = 0.89, P < 0.01), FFM(leg) (r = 0.81, P < 0.05), 1RM squat (r = 0.84, P < 0.05), and type IIA muscle fibre cross sectional area (r = 0.82, P < 0.05) after 14 weeks of resistance training. These results may suggest that p70(S6k) phosphorylation is involved in the signalling events leading to an increase in protein accretion in human skeletal muscle following resistance training, at least during the initial training period.

This study aimed at evaluating whether addition of extensive upper body training in well-trained cross country skiers induces an adaptation of the triceps brachii (TB) muscle and whether this affects performance. Muscle biopsies were obtained from TB muscle in six male elite cross country skiers before and after 20 weeks of increased upper body training. The cross-sectional area of type I and IIA fibers increased by 11.3% and 24.0%, respectively, and so did the number of capillaries per fiber (2.3�3.2) (all P<0.05). SDS-polyacrylamide electrophoresis revealed in single fibers that the number of fibers expressing myosin heavy chain (MHC) type I isoform decreased from 68.7% to 60.9% (P<0.05), MHC I/IIA isoform was unaltered, while MHC IIA fibers increased from 21.6% to 35.7% and the 4.8% MHC IIA/IIX disappeared with the training (both P<0.05). Citrate synthase and 3-hydroxyacyl coenzyme A dehydrogenase activities increased by 23.3% and 15.4%, respectively, and double poling 10 km time-trial by 10.4% (all P<0.05). The values for TB are similar to what has been demonstrated for leg muscles after exercise training. The subjects who demonstrated the largest improvement in performance exhibited the largest muscle adaptation, which, in turn, was related to the pre-maximal oxygen uptake.

immunofluorescence microscopy; western blotting; monocarboxylate transporter; fiber type.

immunofluorescence microscopy; western blotting; monocarboxylate transporter; fiber type.

immunofluorescence microscopy; western blotting; monocarboxylate transporter; fiber type.

Stasinaki, A. N., Gloumis, G., Spengos, K., Blazevich, A. J., Zaras, N., Georgiadis, G., ... & Blazevich, A. (2015). Muscle strength, power and morphological adaptations after 6 weeks of compound vs. complex training in healthy men. Journal of strength and conditioning research 29(9), 2559-2569. Available here