Efeito da suplementação de arginina sobre marcadores indiretos de dano muscular induzido pelo exercício de força / Effect of arginine supplementation on indirect markers of muscle damage induced by resistance exercise

O objetivo do presente estudo foi avaliar o efeito da suplementação de arginina (ARG) sobre marcadores indiretos do dano muscular induzido pelo exercício (DMIE). Participaram do estudo 24 jovens universitários do sexo masculino, com experiência mínima de 1 ano em treinamento de força. Os indivíduos foram alocados em 2 grupos, em seguindo delineamento experimental duplo -cego: suplementado com 7g de arginina (ARG, n=12) ou suplementado com 7g de placebo (PLA, n =12 ). O suplemento foi oferecido 30 min antes da realização do protocolo de 10 séries de 10 repetições máximas (RMs) realizadas no supino. Foram aferidas a circunferência torácica, a dor muscular de in ício tardio (DMIT), por meio da escala visual analógica (EVA), e a carga do teste de uma repetição máxima (1 RM) em repouso, 24h, 48h e 72h após a sessão de treinamento (ST). Os resultados foram analisados utilizando teste de análise de variância ANOVA de dois fatores), seguido pelo teste de Bonferroni. A DMIT apresentou maior magnitude no PLA, em todos momentos avaliados após a ST, em comparação ao grupo ARG (p<0,01). Foi observado maior decréscimo da produção de força no grupo PLA, em 72h após a ST , comparado ao grupo ARG (p<0,05). A suplementação aguda de ARG parece ter atenuado a magnitude da DMIT e acelerado a recuperação da força...(AU)

The purpose of this study was to investigate the effect of arginine (ARG) supplementation o nindirect markers of exercise-induced muscle damage (EIMD). Twenty-four male graduate students, with a minimum of one year of experience in resistance training participated in the study . T he subject s were allocated in 2 groups in a double-blind experimental design: supplemented with 7 g o f argin ine (ARG, n=12) or supplemented with 7g of placebo (PLA, n=12). The dietary supplement was co n sum e d at 3 0 minutes prior to a protocol of 10 sets of 10 maximum repetitions performed in the bench press. Measurements of thoracic circumference, delayed onset muscle soreness (DOMS) using visual an alo gue scale (VAS), and one-repetition maximum (1RM) at rest, 24h, 48h and 72h after the training session (TS). The data were analyzed by ANOVA-two way, followed by the Bonferroni test. DOMS presented a reater magnitude for PLA, in all moments evaluated after TS, compared to the ARG group (p<0.01). There was a greater decrease in the strength for PLA, at 72h after TS, compared to ARG (p<0 .05 ). The acute ARG supplementation seems to attenuate the magnitude of DOMS and accelerate recovery of strength...(AU)

Effect of linear and undulating training periodization models on the repeated sprint ability and strength of soccer players

Purpose: The aim of the study was to investigate the effect of linear and undulating strength-power training scheme on the repeated sprint ability (RSA) and lower body strength of soccer players. Method: Twenty soccer players (under-20 category) were split into 2 groups: the linear load (LL, n=10) and the undulating load (UL, n=10). In the commencement and at the end of the 6-week pre-season period, the RSA test (6 x 35m) and the 1RM parallel squat test (1RMsquat) were conducted. The LL and UL performed the same type and number of sessions. The training stimulus in the strength training was different between LL (Weeks 1 and 2 = Muscular Endurance; Weeks 3 and 4 = Strength; Weeks 5 and 6 = Power) and UL (daily load variation in the same week). Results: A improvement in RSAmean and 1RMsquat was detected in LL and in UL. No significant difference was noted between LL vs UL for all variables. Conclusion: Both groups improved maximal muscle strength in parallel back squat and RSA. UL induced a greater gain in RSA.(AU)

Acute effect of different warm-up interventions on neuromuscular performance of recreational soccer players / Efeito agudo de diferentes intervenções de aquecimento pré-exercício sobre o desempenho neuromuscular de jogadores amadores de futebol

Pre-exercises interventions are frequently implemented in order to maximize athletic performance. In this sense, the aim of this study was to evaluated the effect of three distinct pre-exercise interventions on acute neuromuscular performance in recreational soccer players: 1) parallel squat; 2) static stretching; and 3) ballistic stretching. After all interventions, participants performed a flexibility evaluation (sit-and-reach-test), followed by a squat jump, a counter-movement jump and a 30 meter-sprint test. A one-way analysis of variance revealed: a) a significant decrease in jumping performance was induced by both Stretching conditions when compared to the parallel squat intervention; b) a significant increase in lower limb flexibility after both stretching interventions when compared to parallel squat. In conclusion, it is suggested that a pre-exercise intervention comprised of stretching exercises acutely increase flexibility, while may interfere in jump performance in recreational athletes...(AU)

Intervenções pré-exercício são frequentemente adotadas para maximizar o desempenho atlético. Nesse sentido, o objetivo deste estudo foi avaliar o efeito de três diferentes intervenções pré- exercício sobre o desempenho neuromuscular de jogadores de futebol amadores: 1) agachamento paralelo, 2) alongamento estático e 3) alongamento balístico. Após as intervenções, os participantes realizaram a avaliação de flexibilidade (teste de sentar e alcançar) e, em seguida, o salto com agachamento, o salto com contramovimento e o teste de velocidade de 30 metros. Os resultados da ANOVA one-way revelaram: a) redução significante no desempenho do salto para ambas às condições de alongamento quando comparadas ao agachamento paralelo e b) aumento significante da flexibilidade dos membros inferiores após ambas às intervenções de alongamento em comparação ao achamento paralelo. Em conclusão, sugere-se que as intervenções pré-exercício compostas de exercícios de alongamento aumentam agudamente a flexibilidade, paralelamente, podendo prejudicar o desempenho de saltos de atletas amadores...(AU)

Leucine supplementation improves regeneration of skeletal muscles from old rats.

The decreased regenerative capacity of old skeletal muscles involves disrupted turnover of proteins. This study investigated whether leucine supplementation in old rats could improve muscle regenerative capacity. Young and old male Wistar rats were supplemented with leucine; then, the muscles were cryolesioned and examined after 3 and 10 days. Leucine supplementation attenuated the decrease in the expression of eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1) and eukaryotic translation initiation factor 4E (eIF4E) in young and old muscles on day 3 post-injury and promoted an increase in the cross-sectional area of regenerating myofibers from both young and old soleus muscles on day 10 post-injury. This supplementation decreased the levels of ubiquitinated proteins and increased the proteasome activity in young regenerating muscles, but the opposite effect was observed in old regenerating muscles. Moreover, leucine decreased the inflammation area and induced an increase in the number of proliferating satellite cells in both young and old muscles. Our results suggest that leucine supplementation improves the regeneration of skeletal muscles from old rats, through the preservation of certain biological responses upon leucine supplementation. Such responses comprise the decrease in the inflammation area, increase in the number of proliferating satellite cells and size of regenerating myofibers, combined with the modulation of components of the phosphoinositide 3-kinase/Akt-protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathway and ubiquitin-proteasome system.

Effects of concurrent strength and endurance training on genes related to myostatin signaling pathway and muscle fiber responses.

Concurrent training (CT) seems to impair training-induced muscle hypertrophy. This study compared the effects of CT, strength training (ST) and interval training (IT) on the muscle fiber cross-sectional area (CSA) response, and on the expression of selected genes involved in the myostatin (MSTN) signaling mRNA levels. Thirty-seven physically active men were randomly divided into 4 groups: CT (n = 11), ST (n = 11), IT (n = 8), and control group (C) (n = 7) and underwent an 8-week training period. Vastus lateralis biopsy muscle samples were obtained at baseline and 48 hours after the last training session. Muscle fiber CSA, selected genes expression, and maximum dynamic ST (1 repetition maximum) were evaluated before and after training. Type IIa and type I muscle fiber CSA increased from pre- to posttest only in the ST group (17.08 and 17.9%, respectively). The SMAD-7 gene expression significantly increased at the posttest in the ST (53.9%) and CT groups (39.3%). The MSTN and its regulatory genes ActIIb, FLST-3, FOXO-3a, and GASP-1 mRNA levels remained unchanged across time and groups. One repetition maximum increased from pre- to posttest in both the ST and CT groups (ST = 18.5%; CT = 17.6%). Our findings are suggestive that MSTN and their regulatory genes at transcript level cannot differentiate muscle fiber CSA responses between CT and ST regimens in humans.

Maximum number of repetitions performed by resistance-trained men: effect of maximum load intensity and exercise selection / Número máximo de repetições realizadas por homens treinados em força: efeitos da intensidade máxima de carga e escolha do exercício / El número máximo de repeticiones realizadas por hombres entrenados: efecto de la intensidad de carga máxima y la selección de los ejercicios

The purpose of this study was to compare the number of maximum repetitions (RMs) performed at 80% of one-repetition maximum (1RM) and 80% of one-repetition maximum eccentric (1RMecc) test for the preacher-curl (PC) and the bench-press (BP) exercises. Fifteen resistance-trained men participated in this counterbalanced-crossover study. There was no significant difference in the number of RMs performed at 80%-1RM (PC: 7.0±1.2 RMs and BP: 5.8±1.3 RMs) and 80%-1RMecc (PC: 6.0±1.1 RMs and BP: 5.4±1.1 RMs) for both exercises. No significant difference in the numbers of RMs was detected between the PC (80%-1RM: 7.0±1.2 RMs and 80%-1RMecc: 6.0±1.1 RMs) and BP exercises (80%-1RM: 5.8±1.3 RMs and 80%-1RMecc: 5.4±1.1 RMs) for both intensities. In conclusion, the number of RMs performed by resistance-trained men was not affected by the maximum load intensity based on muscle action and the exercise selection...

O objetivo deste estudo foi comparar o número de repetições máximas (RMs) realizadas com intensidade de 80% dos testes de uma repetição máxima (1RM) e 80% de uma repetição máxima excêntrica (1RMecc) para os exercícios supino-horizontal (SH) e rosca-scott (RS). Quinze homens com experiência em treinamento de força participaram desse estudo randomizado cruzado. Não houve diferença significativa no número de RMs realizadas a 80%-1RM (RS: 7,0±1,2 RMs e SH: 5,8±1,2 RMs) e 80%-1RMecc (RS: 6,0±1,1 RMs e SH: 5,4±1,1 RMs) para ambos os exercícios. Não foi detectada diferença significativa no número de RMs entre o exercício RS (80%-1RM: 7,0±1,2 RMs and 80%-1RMecc: 6,0±1,1 RMs) e SH (80%-1RM: 5,8 ±1,2 RMs and 80%-1RMecc: 5,4±1,1 RMs) para ambas intensidades. Em conclusão, o número de RMs realizados por homens treinados em força não foi afetado pela intensidade máxima da carga baseada na ação muscular e pela seleção de exercícios...

El objetivo de este estudio fue comparar el número de repeticiones máximas (RMS) realizado con una intensidad de 80% de una repetición máxima (1RM) y el 80% de una repetición máxima excéntrica (1RMecc) para el ejercicio supino horizontal (SH) y rosca scott (RS). Quince hombres con experiencia en el entrenamiento de fuerza participaron en este estudio cruzado aleatorio. No hubo diferencia significativa en el número de los RMs realizado a 80% 1RM (RS: 7,0±1,2 RMs e SH: 5,8±1,2 RMs) y 80%-1RMecc (RS: 6,0±1,1 RMs e SH: 5,4±1,1 RMs) para ambos ejercicios. No se detectó diferencia significativa en el número de los RMs entre el ejercicio RS (80%- 1RM: 7,0±1,2 RMs and 80%-1RMecc: 6,0±1,1 RMs) y SH (80%-1RM: 5,8 ±1,2 RMs and 80%-1RMecc: 5,4±1,1 RMs) para ambas intensidades. En conclusión, el número de RMs realizados por hombres entrenados en la fuerza no afectó la intensidad máxima de la carga basada en la acción muscular y la selección de los ejercicios...

Leucine supplementation improves skeletal muscle regeneration after cryolesion in rats.

This study was undertaken in order to provide further insight into the role of leucine supplementation in the skeletal muscle regeneration process, focusing on myofiber size and strength recovery. Young (2-month-old) rats were subjected or not to leucine supplementation (1.35 g/kg per day) started 3 days prior to cryolesion. Then, soleus muscles were cryolesioned and continued receiving leucine supplementation until 1, 3 and 10 days later. Soleus muscles from leucine-supplemented animals displayed an increase in myofiber size and a reduction in collagen type III expression on post-cryolesion day 10. Leucine was also effective in reducing FOXO3a activation and ubiquitinated protein accumulation in muscles at post-cryolesion days 3 and 10. In addition, leucine supplementation minimized the cryolesion-induced decrease in tetanic strength and increase in fatigue in regenerating muscles at post-cryolesion day 10. These beneficial effects of leucine were not accompanied by activation of any elements of the phosphoinositide 3-kinase/Akt/mechanistic target of rapamycin signalling pathway in the regenerating muscles. Our results show that leucine improves myofiber size gain and strength recovery in regenerating soleus muscles through attenuation of protein ubiquitination. In addition, leucine might have therapeutic effects for muscle recovery following injury and in some muscle diseases.

Leucine and HMB differentially modulate proteasome system in skeletal muscle under different sarcopenic conditions.

In the present study we have compared the effects of leucine supplementation and its metabolite ß-hydroxy-ß-methyl butyrate (HMB) on the ubiquitin-proteasome system and the PI3K/Akt pathway during two distinct atrophic conditions, hindlimb immobilization and dexamethasone treatment. Leucine supplementation was able to minimize the reduction in rat soleus mass driven by immobilization. On the other hand, leucine supplementation was unable to provide protection against soleus mass loss in dexamethasone treated rats. Interestingly, HMB supplementation was unable to provide protection against mass loss in all treatments. While solely fiber type I cross sectional area (CSA) was protected in immobilized soleus of leucine-supplemented rats, none of the fiber types were protected by leucine supplementation in rats under dexamethasone treatment. In addition and in line with muscle mass results, HMB treatment did not attenuate CSA decrease in all fiber types against either immobilization or dexamethasone treatment. While leucine supplementation was able to minimize increased expression of both Mafbx/Atrogin and MuRF1 in immobilized rats, leucine was only able to minimize Mafbx/Atrogin in dexamethasone treated rats. In contrast, HMB was unable to restrain the increase in those atrogenes in immobilized rats, but in dexamethasone treated rats, HMB minimized increased expression of Mafbx/Atrogin. The amount of ubiquitinated proteins, as expected, was increased in immobilized and dexamethasone treated rats and only leucine was able to block this increase in immobilized rats but not in dexamethasone treated rats. Leucine supplementation maintained soleus tetanic peak force in immobilized rats at normal level. On the other hand, HMB treatment failed to maintain tetanic peak force regardless of treatment. The present data suggested that the anti-atrophic effects of leucine are not mediated by its metabolite HMB.

The ß2-adrenoceptor agonist formoterol improves structural and functional regenerative capacity of skeletal muscles from aged rat at the early stages of postinjury.

Skeletal muscles from old rats fail to completely regenerate following injury. This study investigated whether pharmacological stimulation of ß2-adrenoceptors in aged muscles following injury could improve their regenerative capacity, focusing on myofiber size recovery. Young and aged rats were treated with a subcutaneous injection of ß2-adrenergic agonist formoterol (2 µg/kg/d) up to 10 and 21 days after soleus muscle injury. Formoterol-treated muscles from old rats evaluated at 10 and 21 days postinjury showed reduced inflammation and connective tissue but a similar number of regenerating myofibers of greater caliber when compared with their injured controls. Formoterol minimized the decrease in tetanic force and increased protein synthesis and mammalian target of rapamycin phosphorylation in old muscles at 10 days postinjury. Our results suggest that formoterol improves structural and functional regenerative capacity of regenerating skeletal muscles from aged rats by increasing protein synthesis via mammalian target of rapamycin activation. Furthermore, formoterol may have therapeutic benefits in recovery following muscle damage in senescent individuals.

Effect of eccentric exercise velocity on akt/mtor/p70(s6k) signaling in human skeletal muscle.

It has been suggested that muscle tension plays a major role in the activation of intracellular pathways for skeletal muscle hypertrophy via an increase in mechano growth factor (MGF) and other downstream targets. Eccentric exercise (EE) imposes a greater amount of tension on the active muscle. In particular, high-speed EE seems to exert an additional effect on muscle tension and, thus, on muscle hypertrophy. However, little is known about the effect of EE velocity on hypertrophy signaling. This study investigated the effect of acute EE-velocity manipulation on the Akt/mTORCI/p70(S6K) hypertrophy pathway. Twenty subjects were assigned to either a slow (20°·s(-1); ES) or fast EE (210°·s(-1); EF) group. Biopsies were taken from vastus lateralis at baseline (B), immediately after (T1), and 2 h after (T2) the completion of 5 sets of 8 repetitions of eccentric knee extensions. Akt, mTOR, and p70(S6K) total protein were similar between groups, and did not change postintervention. Further, Akt and p70(S6K) protein phosphorylation were higher at T2 than at B for ES and EF. MGF messenger RNA was similar between groups, and only significantly higher at T2 than at B in ES. The acute manipulation of EE velocity does not seem to differently influence intracellular hypertrophy signaling through the Akt/mTORCI/p70S6K pathway.

Mammalian target of rapamycin complex 1 is involved in differentiation of regenerating myofibers in vivo.

This work was undertaken to provide further insight into the role of mammalian target of rapamycin complex 1 (mTORC1) in skeletal muscle regeneration, focusing on myofiber size recovery. Rats were treated or not with rapamycin, an mTORC1 inhibitor. Soleus muscles were then subjected to cryolesion and analyzed 1, 10, and 21 days later. A decrease in soleus myofiber cross-section area on post-cryolesion days 10 and 21 was accentuated by rapamycin, which was also effective in reducing protein synthesis in these freeze-injured muscles. The incidence of proliferating satellite cells during regeneration was unaltered by rapamycin, although immunolabeling for neonatal myosin heavy chain (MHC) was weaker in cryolesion+rapamycin muscles than in cryolesion-only muscles. In addition, the decline in tetanic contraction of freeze-injured muscles was accentuated by rapamycin. This study indicates that mTORC1 plays a key role in the recovery of muscle mass and the differentiation of regenerating myofibers, independently of necrosis and satellite cell proliferation mechanisms.

A TRbeta-selective agonist confers resistance to diet-induced obesity.

Thyroid hormone receptor beta (TRbeta also listed as THRB on the MGI Database)-selective agonists activate brown adipose tissue (BAT) thermogenesis, while only minimally affecting cardiac activity or lean body mass. Here, we tested the hypothesis that daily administration of the TRbeta agonist GC-24 prevents the metabolic alterations associated with a hypercaloric diet. Rats were placed on a high-fat diet and after a month exhibited increased body weight (BW) and adiposity, fasting hyperglycemia and glucose intolerance, increased plasma levels of triglycerides, cholesterol, nonesterified fatty acids and interleukin-6. While GC-24 administration to these animals did not affect food ingestion or modified the progression of BW gain, it did increase energy expenditure, eliminating the increase in adiposity without causing cardiac hypertrophy. Fasting hyperglycemia remained unchanged, but treatment with GC-24 improved glucose tolerance by increasing insulin sensitivity, and also normalized plasma triglyceride levels. Plasma cholesterol levels were only partially normalized and liver cholesterol content remained high in the GC-24-treated animals. Gene expression in liver, skeletal muscle, and white adipose tissue was only minimally affected by treatment with GC-24, with the main target being BAT. In conclusion, during high-fat feeding treatment with the TRbeta-selective agonist, GC-24 only partially improves metabolic control probably as a result of accelerating the resting metabolic rate.

Effect of bench press exercise intensity on muscle soreness and inflammatory mediators.

This study compared four different intensities of a bench press exercise for muscle soreness, creatine kinase activity, interleukin (IL)-1beta, IL-6, tumor necrosis factor-alpha (TNF-alpha), and prostaglandin E(2) (PGE(2)) concentrations in the blood. Thirty-five male Brazilian Army soldiers were randomly assigned to one of five groups: 50% one-repetition maximum (1-RM), 75% 1-RM, 90% 1-RM, 110% 1-RM, and a control group that did not perform the exercise. The total volume (sets x repetitions x load) of the exercise was matched among the exercise groups. Muscle soreness and plasma creatine kinase activity increased markedly (P < 0.05) after exercise, with no significant differences among the groups. Serum PGE(2) concentration also increased markedly (P < 0.05) after exercise, with a significantly (P < 0.05) greater increase in the 110% 1-RM group compared with the other groups. A weak but significant (P < 0.05) correlation was found between peak muscle soreness and peak PGE(2) concentration, but no significant correlation was evident between peak muscle soreness and peak creatine kinase activity, or peak creatine kinase activity and peak PGE(2) concentration. All groups showed no changes in IL-1beta, IL-6 or TNF-alpha. Our results suggest that the intensity of bench press exercise does not affect the magnitude of muscle soreness and blood markers of muscle damage and inflammation.

Thyroid hormone receptor-beta-selective agonist GC-24 spares skeletal muscle type I to II fiber shift.

Triiodothyronine (T3) is known to play a key role in the function of several tissues/organs via the thyroid hormone receptor isoforms alpha (TRalpha) and beta (TRbeta). We have investigated the effects of GC-24, a novel synthetic TRbeta-selective compound, on skeletal muscle fiber-type determination, cross-sectional area, and gene expression in rat skeletal muscles. For fiber typing, cross sections of soleus and extensor digitorum longus (EDL) muscles were stained for myosin ATPase activity at various pHs. Serum T3, T4, and cholesterol levels were also determined. Analysis of highly T3-responsive genes, viz., myosin heavy chain IIa (MHCIIa) and sarcoendoplasmic reticulum adenosine triphosphatase (SERCA1), was performed by quantitative real-time polymerase chain reaction. Equimolar doses of T3 and GC-24 had a similar cholesterol-lowering effect. T3, but not GC-24, decreased fiber type I and increased fiber type II abundance in soleus and EDL muscles. Conversely, in EDL, both T3 and GC-24 decreased the mean cross-sectional area of type I fibers. MHCIIa gene expression was reduced (approximately 50%) by T3 and unchanged by GC-24. SERCA1 gene expression was strongly induced by T3 (approximately 20-fold) and mildly induced by GC-24 (approximately two-fold). These results show that GC-24 does not significantly alter the composition of skeletal muscle fiber type and further strengthens the putative use of GC compounds as therapeutic agents.

Expression of tropism-related genes in regenerating skeletal muscle of rats treated with cyclosporin-A.

This work was undertaken to provide further insights into the expression of tropism-related genes in regenerating skeletal muscle of adult rats treated with cyclosporin-A (CsA), a calcineurin inhibitor. Rats were treated with CsA for 5 days and, on the 6th day, were submitted to cryolesion of the soleus muscles. CsA treatment continued for 1, 10, and 21 days after cryolesion. Muscles were removed, frozen, and stored in liquid nitrogen. Body and muscle weights, histological sections stained with toluidine blue, and gene expression of the regeneration molecular markers, viz., desmin and neonatal myosin heavy chain, were assessed to confirm that cryolesion and CsA treatment were effective during the allowed regeneration time. Quantitative reverse transcription/polymerase chain reaction demonstrated that myostatin gene expression was not altered by either cryolesion or CsA treatment combined with cryolesion. Calpain-3 gene expression decreased at 1 day after cryolesion and also following CsA treatment combined with cryolesion. However, calpain-3 gene expression was strongly up-regulated (approximately five-fold) 10 days after cryolesion and returned to control levels at day 21. CsA treatment blocked calpain-3 gene expression rise induced by 10 days of cryolesion. Atrogin-1 gene expression was decreased at 1 day after cryolesion and following cryolesion combined with CsA treatment, returning to control levels at day 10. These results suggest that (1) calpain-3 has a differential role in the early and late stages of regeneration in a calcineurin-dependent manner, and (2) atrogin-1 is involved in the early stages of regeneration independently of calcineurin.