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The current study explored whether the marked hypertrophic response noted with a short-term unilateral concurrent exercise paradigm was associated with more prominent changes in myonuclei accretion, ribosome biogenesis, and capillarization compared with resistance exercise alone (RE). Ten men (age 25 ± 4 yr) performed aerobic and resistance exercise (AE + RE) for one leg while the other leg did RE. Muscle biopsies were obtained before and after 5 wk of training and subjected to fiber-type specific immunohistochemical analysis, and quantification of total RNA content and mRNA/rRNA transcript abundance. Type II fiber cross-sectional area (CSA) increased with both AE + RE (22%) and RE (16%), while type I fiber CSA increased mainly with AE + RE (16%). The change score tended to differ between legs for type I CSA (P = 0.099), and the increase in smallest fiber diameter was greater in AE + RE than RE (P = 0.029). The number of nuclei per fiber increased after AE + RE in both fiber types, and this increase was greater (P = 0.027) than after RE. A strong correlation was observed between changes in number of nuclei per fiber and fiber CSA in both fiber types, for both AE + RE and RE (r > 0.8, P < 0.004). RNA content increased after AE + RE (24%, P = 0.019), but the change-scores did not differ across legs. The capillary variables generally increased in both fiber types, with no difference across legs. In conclusion, the accentuated hypertrophic response to AE + RE was associated with more pronounced myonuclear accretion, which was strongly correlated with the degree of fiber hypertrophy. This suggests that myonuclear accretion could play a role in facilitating muscle hypertrophy also during very short training periods. [ABSTRACT FROM AUTHOR]

The current study examined the effects of a preceding bout of aerobic exercise (AE) on subsequent molecular signaling to resistance exercise (RE) of the elbow extensors. Eleven men performed unilateral elbow-extensor AE (~45 min at 70% peak workload) followed by unilateral RE (4 × 7 maximal repetitions) for both arms. Thus, one arm performed AE+RE interspersed with 15 min recovery, whereas the other arm conducted RE alone. Muscle biopsies were taken from the triceps brachii of each arm immediately before (PRE) and 15 min (POST1) and 3 h (POST2) after RE. Molecular markers involved in translation initiation, protein breakdown, mechanosignaling, and ribosome biogenesis were analyzed. Peak power during RE was reduced by 24% (±19%) when preceded by AE (P < 0.05). Increases in PGC1a and MuRF1 expression were greater from PRE to POST2 in AE+RE compared with RE (18-vs. 3.5- and 4- vs. 2-fold, respectively, interaction, P < 0.05). Myostatin mRNA decreased in both arms (P < 0.05). Phosphorylation of AMPK (Thr172) increased (2.5-fold), and 4E-BP1 (Thr37/46) decreased (2.0-fold), after AE (interactions, P < 0.05). p70 S6K, yesassociated protein, and c-Jun NH2-terminal kinase phosphorylation were unaltered, whereas focal adhesion kinase decreased ~1.5-fold, and β1- integrin increased ~1.3- to 1.5-fold, (time effect, P < 0.05). Abundance of 45S pre-ribosomal (r)RNA (internally transcribed spacer, ITS) decreased (~30%) after AE (interaction, P < 0.05), whereas CMYC mRNA was greater in AE+RE compared with RE (12-fold, P < 0.05). POLR1B abundance increased after both AE+RE and RE. All together, our results suggest that a single bout of AE leads to an immediate decrease in signaling for translation initiation and ribosome biogenesis. Yet, this did not translate into altered RE-induced signaling during the 3-h postexercise recovery period. [ABSTRACT FROM AUTHOR]

In the quest for a viable non-gravity dependent method to "lift weights" in space, our laboratory introduced iso-inertial resistance (YoYo™) exercise using spinning flywheel(s), more than 25 years ago. After being thoroughly tested in individuals subjected to various established spaceflight analogs, a multi-mode YoYo™ exercise apparatus was eventually installed on the International Space Station in 2009. The method, applicable to any muscle group, provides accommodated resistance and optimal muscle loading through the full range of motion of concentric actions, and brief episodes of eccentric overload. This exercise intervention has found terrestrial applications and shown success in enhancing sports performance and preventing injury and aiding neurological or orthopedic rehabilitation. Research has proven that this technique offers unique physiological responses not possible with other exercise hardware solutions. This paper provides a brief overview of research that has made use, and explored the efficacy, of this method in healthy sedentary or physically active individuals and populations suffering from muscle wasting, disease or injury. While the collective evidence to date suggests YoYo™ offers a potent stimulus to optimize the benefits of resistance exercise, systematic research to support clinical use of this method has only begun to emerge. Thus, we also offer perspectives on unresolved issues, unexplored applications for clinical conditions, and how this particular exercise paradigm could be implemented in future clinical research and eventually being prescribed. Fields of particular interest are those aimed at promoting muscle health by preventing injury or combating muscle wasting and neurological or metabolic dysfunction due to aging or illness, or those serving in rehabilitation following trauma and/or surgery. [ABSTRACT FROM AUTHOR]

Background: Resistance exercise (RE) improves neuromuscular function and physical performance after stroke. Yet, the effects of RE emphasizing eccentric (ECC; lengthening) actions on muscle hypertrophy and cognitive function in stroke patients are currently unknown. Thus, this study explored the effects of ECC-overload RE training on skeletal muscle size and function, and cognitive performance in individuals with stroke. Methods: Thirty-two individuals with chronic stroke (≥6 months post-stroke) were randomly assigned into a training group (TG; n = 16) performing ECC-overload flywheel RE of the more-affected lower limb (12 weeks, 2 times/week; 4 sets of 7 maximal closed-chain knee extensions; <2 min of contractile activity per session) or a control group (CG; n = 16), maintaining daily routines. Before and after the intervention, quadriceps femoris volume, maximal force and power for each leg were assessed, and functional and dual task performance, and cognitive functions were measured. Results: Quadriceps femoris volume of the more-affected leg increased by 9.4 % in TG. Muscle power of the more-affected, trained (48.2 %), and the less-affected, untrained limb (28.1 %) increased after training. TG showed enhanced balance (8.9 %), gait performance (10.6 %), dual-task performance, executive functions (working memory, verbal fluency tasks), attention, and speed of information processing. CG showed no changes. Conclusion: ECC-overload flywheel resistance exercise comprising 4 min of contractile activity per week offers a powerful aid to regain muscle mass and function, and functional performance in individuals with stroke. While the current intervention improved cognitive functions, the cause-effect relationship, if any, with the concomitant neuromuscular adaptations remains to be explored. Trial Registration: Clinical Trials NCT02120846. [ABSTRACT FROM AUTHOR]

Purpose: This study assessed markers of muscle damage and training adaptations to eccentric-overload flywheel resistance exercise (RE) in men and women. Methods: Dynamic strength (1 RM), jump performance, maximal power at different percentages of 1 RM, and muscle mass in three different portions of the thigh were assessed in 16 men and 16 women before and after 6 weeks (15 sessions) of flywheel supine squat RE training. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured before, 24, 48 and 72 h after the first and the last training session. Results: After training, increases in 1 RM were somewhat greater (interaction P < 0.001) in men (25 %) than in women (20 %). Squat and drop jump height and power performance at 50, 60, 70 and 80 % of 1 RM increased after training in both sexes ( P < 0.05). Power improvement at 80 % of 1 RM was greater (interaction P < 0.02) in men than women. Muscle mass increased ~5 % in both groups ( P < 0.05). CK increased in men after the first training session ( P < 0.001), whereas the response in women was unaltered. In both sexes, LDH concentration was greater after the first training session compared with basal values ( P < 0.05). After the last session, CK and LDH remained at baseline in both groups. Conclusions: These results suggest that although improvements in maximal strength and power at high loads may be slightly greater for men, eccentric-overload RE training induces comparable and favorable gains in strength, power, and muscle mass in both men and women. Equally important, it appears muscle damage does not interfere with the adaptations triggered by this training paradigm. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the responses of women to the repeated bout effect (RBE) and to a short eccentric training program. Twenty-four young females were randomly assigned to a training group (TG, n = 14) or a control group (CG, n = 10). They performed two identical acute eccentric bouts (120 repetitions at 70% of 1RM) in a leg-press device in an 8 weeks interval. TG followed a 4-week-eccentric-training program between the bouts. Maximal isometric contraction, range of motion, peak power and quadriceps muscle soreness were compared between and within groups before and after the two acute eccentric bouts. TG and CG presented significant losses of isometric strength and peak power, and an increment in soreness after the first bout. Isometric strength and peak power were recovered faster in CG after the second bout (p < 0.05) compared with TG, which showed a similar recovery of these parameters after the second bout compared with the first one. A decrease in soreness and a faster recovery of range of motion were found in TG (p < 0.05) following the second bout compared with the first one, but not in CG. Data indicate that a 4-week eccentric training program may prevent the RBE over those adaptations related with muscle damage (e.g. strength loss), but it may increase RBE impact on inflammatory processes (e.g. soreness). [ABSTRACT FROM AUTHOR]