Article

The effects of acute branched-chain amino acid supplementation on recovery from a single bout of hypertrophy exercise in resistance-trained athletes

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Abstract

This study investigated the effects of acute branched-chain amino acid (BCAA) supplementation on recovery from exercise-induced muscle damage, among experienced resistance-trained athletes. In a double-blind matched-pairs design, 16 resistance-trained participants, routinely performing hypertrophy training, were randomly assigned to a BCAA (n = 8) or placebo (n = 8) group. The BCAAs were administered at a dosage of 0.087 g/kg body mass, with a 2:1:1 ratio of leucine, isoleucine and valine. The participants performed 6 sets of 10 full-squats at 70 % 1RM to induce muscle damage. All participants were diet-controlled across the study. Creatine kinase (CK), peak isometric knee-extensor force, perceived muscle soreness and counter-movement jump (CMJ) height were measured immediately before (baseline), 1-h, 24-h and 48-h post-exercise. There were large to very large time effects for all measurements between baseline and 24-48 h. Between-group comparisons, expressed as a percentage of baseline, revealed differences in isometric strength at 24-h (Placebo ~87% c.f. BCAA ~92 %; moderate, likely), CMJ at 24-h (Placebo ~93 % c.f. BCAA ~96 %; small, likely) and muscle soreness at both 24-h (Placebo ~685 % c.f. BCAA ~531 %; small, likely) and 48-h (Placebo ~468 % c.f. BCAA ~350 %; small, likely). Acute supplementation of BCAAs (0.087 g/kg) increased the rate of recovery in isometric strength, CMJ height and perceived muscle soreness compared to placebo after a hypertrophy-based training session among diet-controlled, resistance-trained athletes. These findings question the need for longer BCAA loading phases and highlight the importance of dietary control in studies of this type.

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... Accordingly, supplementation with BCAAs, either acutely or for 12 days pre-exercise, has been linked with post-exercise reductions in blood indicators of muscle damage, such as CK, ammonia, lactate dehydrogenase (LDH) and myoglobin [99][100][101][102]. These changes have been associated with enhanced post-exercise muscle function recovery and decreased muscle soreness following repeated drop jumps [100] and maximal resistance-based exercise tasks [102][103][104]. ...
... In a review of the literature on BCAA supplementation [105], it was recommended that, for maximal benefit, supplementation with BCAA should occur for at least 1 week prior to exercise with additional doses on the day of exercise and supplementation on follow-up days. However, changes in markers of muscle damage have also been seen with relatively low BCAA doses of~5.4-8.3 g consumed acutely prior to exercise [101,104]. Typically, BCAA supplements are made up of leucine, isoleucine and valine in a 2:1:1 ratio [100,101,104,106]. However, based on research associating the leucine component with changes in inflammatory processes in skeletal muscle [107], and given the reported competition between leucine, isoleucine and valine for cellular transport and metabolic processes, it has been suggested that supplementation with leucine alone may be sufficient to provide benefits to post-exercise recovery [108]. ...
... However, changes in markers of muscle damage have also been seen with relatively low BCAA doses of~5.4-8.3 g consumed acutely prior to exercise [101,104]. Typically, BCAA supplements are made up of leucine, isoleucine and valine in a 2:1:1 ratio [100,101,104,106]. However, based on research associating the leucine component with changes in inflammatory processes in skeletal muscle [107], and given the reported competition between leucine, isoleucine and valine for cellular transport and metabolic processes, it has been suggested that supplementation with leucine alone may be sufficient to provide benefits to post-exercise recovery [108]. ...
Article
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The metabolic and mechanical stresses associated with muscle-fatiguing exercise result in perturbations to bodily tissues that lead to exercise-induced muscle damage (EIMD), a state of fatigue involving oxidative stress and inflammation that is accompanied by muscle weakness, pain and a reduced ability to perform subsequent training sessions or competitions. This review collates evidence from previous research on a wide range of nutritional compounds that have the potential to speed up post-exercise recovery. We show that of the numerous compounds investigated thus far, only two—tart cherry and omega-3 fatty acids—are supported by substantial research evidence. Further studies are required to clarify the potential effects of other compounds presented here, many of which have been used since ancient times to treat conditions associated with inflammation and disease.
... Different outcomes were used to examine the impact of BCAA supplementation among athletes. The studies have investigated the effect of BCAAs on performance [21,[25][26][27][28][29][30][31], body composition [25,26], muscle soreness or recovery [21,[25][26][27][28][29][30][31][32][33][34][35][36][37] and changes in biochemical, hormonal, or molecular signaling [20,21,[25][26][27][28][29][30]33,34,36,[38][39][40][41][42][43]. ...
... Different outcomes were used to examine the impact of BCAA supplementation among athletes. The studies have investigated the effect of BCAAs on performance [21,[25][26][27][28][29][30][31], body composition [25,26], muscle soreness or recovery [21,[25][26][27][28][29][30][31][32][33][34][35][36][37] and changes in biochemical, hormonal, or molecular signaling [20,21,[25][26][27][28][29][30]33,34,36,[38][39][40][41][42][43]. ...
... Two studies examined the influence of BCAAs on specific outputs after an intense bout of exercise, promoting glycogenic depletion [20,21]. A muscledamaging protocol was applied in resistance athletes and strength, jump performance, creatine kinase, muscle soreness were assessed after acute BCAA supplementation [36]. A separate investigation measured the impact of BCAAs on body weight, body composition, strength parameters and resting metabolic rate using a carbohydrate restrictive diet [27]. ...
Article
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Branched-chain amino acids (BCAAs) are oxidized in the muscle and result in stimulating anabolic signals—which in return may optimize performance, body composition and recovery. Meanwhile, among athletes, the evidence about BCAA supplementation is not clear. The aim of this study was to review the effects of BCAAs in athletic populations. The research was conducted in three databases: Web of Science (all databases), PubMed and Scopus. The inclusion criteria involved participants classified both as athletes and people who train regularly, and who were orally supplemented with BCAAs. The risk of bias was individually assessed for each study using the revised Cochrane risk of bias tool for randomized trials (RoB 2.0). From the 2298 records found, 24 studies met the inclusion criteria. Although BCAAs tended to activate anabolic signals, the benefits on performance and body composition were negligible. On the other hand, studies that included resistance participants showed that BCAAs attenuated muscle soreness after exercise, while in endurance sports the findings were inconsistent. The protocols of BCAA supplements differed considerably between studies. Moreover, most of the studies did not report the total protein intake across the day and, consequently, the benefits of BCAAs should be interpreted with caution.
... The effects of BCAA on preventing DOMS caused by EIMD is under debate in the literature since some studies demonstrated that BCAA intake decreased muscle soreness (Howatson et al. 2012;Shimomura et al. 2010;Waldron et al. 2017), while others reported no effects (Ra et al. 2013(Ra et al. , 2018, or even increased DOMS symptoms (Kirby et al. 2012;Osmond et al. 2019) after a bout of EIMD. However, different BCAA content and amino acid ratios, dose, time of treatment, type of EIMD protocol, and subject characteristics may account for the controversial results observed in the literature. ...
... Six (60%) studies investigated untrained or sedentary subjects (Foure et al. 2016;Greer et al. 2007;Kirby et al. 2012;Ra et al. 2013;Ra et al. 2018;Shimomura et al. 2010). Recreationally resistancetrained participants were reported in three (30%) studies (VanDusseldorp et al. 2018;Waldron et al. 2017Waldron et al. , 2018 and one (10%) study included athletes (soccer, rugby) (Howatson et al. 2012). ...
... Six studies induced EIMD with eccentric resistance exercises (n = 6, 60%) (Kirby et al. 2012;Ra et al. 2013Ra et al. , 2018Shimomura et al. 2010;VanDusseldorp et al. 2018;Waldron et al. 2017) (Table 1). Three studies employed eccentric resistance exercises at high intensity and low volume in leg press (120% 1RM) (Kirby et al. 2012) and elbow extension (90% maximal voluntary isometric contraction) (Ra et al. 2013(Ra et al. , 2018. ...
Article
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Branched-chain amino acids (BCAA) are used as a recovery method after exercise-induced muscle damage (EIMD). Although data suggest that BCAA may alleviate the delayed-onset muscle soreness (DOMS) evoked by EIMD, there is no consensus about the most effective supplementation protocol. To investigate the effects of BCAA on DOMS after a single exercise session that caused EIMD, a systematic review and meta-analysis were conducted on the effectiveness of BCAA supplementation to reduce DOMS symptoms in healthy subjects after a single session of EIMD. Randomized clinical trials (RCT) were searched in Medline, Cochrane Library, Science Direct, SciELO, LILACS, SciVerse Scopus, Springer Link journals, Wiley Online Library, and Scholar Google, until May 2021. Ten RCTs were included in the systematic review and nine in the meta-analysis. Seven studies demonstrated that BCAA reduced DOMS after 24 to 72 h. BCAA doses of up to 255 mg/kg/day, or in trained subjects, for mild to moderate EIMD, could blunt DOMS symptoms. However, high variability between studies due to training status, different doses, time of treatment, and severity of EIMD do not allow us to conclude whether BCAA supplementation is efficient in untrained subjects, applied acutely or during a period of pre to post days of EIMD, and at higher doses (> 255 mg/kg/day). The overall effects of BCAA on DOMS after a single session of exercise were considered useful for improving muscle recovery by reducing DOMS in trained subjects, at low doses, in mild to moderate EIMD, and should not be administered only after the EIMD protocol.
... O consumo de suplementos nutricionais tem sido uma das estratégias mais utilizadas, tanto para minimizar os sintomas e prejuízos associados ao DMIE, quanto para acelerar a recuperação de sessõe s de TF 5. . Nesse sentido, alguns estudos com aminoácidos têm reportado resultados promissores 6,7,8 . Howatson et al. 6 reportaram diminuição no aumento da atividade da creatina quinase (CK) plasmática, redução na dor muscular de início tardio (DMIT) e atenua ção no decréscimo da força isométrica máxima em indivíduos submetidos ao protocolo de treinamento físico intenso, que foram suplementados com aminoácidos de cadeia ramificada (ACR) de forma crônica (10g de ACR, duas vezes ao dia, por 7 dias antes do protocolo de treinamento físico, fase de saturação, e nos 5 dias seguintes, incluindo o dia de treinamento). ...
... Já no estudo de Shinomura et al. 7 , foi observada redução da DMIT, atenuação da concentração de mioglobina e menor elevação da elastase (índice de ativação de neutrófilos) após a dose aguda de ACR antes do exercício (100mg/kg de peso, ~5,5g, 15 minutos antes do protocolo de exercício). Alinhado a esses resultados, Waldron et al. 8 Kirby et al. 9 , fazendo uso da suplementação com leucina de forma isolada (250mg/kg de peso antes, durante e após o protocolo de exercício e antes de cada avaliação no período de recuperação), também demonstraram atenuação no decréscimo na força isométrica, em resposta à prática de saltos em profundidade em conjunto com a sessão de TF. Além disso, o metabólito da leucina, denominado Hidroxi-β-Metilburitato (HMβ), vem sendo investigado pelo seu possível papel na redução do DMIE 10,11 . ...
... Efeitos benéficos na percepção da DMIT com o uso de aminoácidos já foram previamente reportados na literatura [7][8][9] . ...
Article
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O objetivo do presente estudo foi avaliar os efeitos da suplementação com o aminoácido 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 randomizados em 2 grupos, em experimento duplo-cego: suplementado com 7g de arginina (ARG, n=12) ou suplementado com 7g de placebo (PLA, n=12) 30 minutos antes à realização do protocolo de 10 séries de 10 repetições máximas (RMs). Foram aferidas a circunferência torácica, a dor muscular de início tardio (DMIT) por meio da escala visual analógica (EVA), e teste de uma repetição máxima (1RM) 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 caminhos) seguido pelo teste de Bonferroni. Foi observado maior decréscimo da produção de força em 72h após a ST no grupo PLA comparado ao grupo ARG (p
... Supplementary digital Material 1 (Supplementary Table i) lists the characteristics of Bcaa supplementation (amount, timing, and duration of consumption) and the number of experimental groups in each study. 24,28,32,40,41,[46][47][48][49][50][51][52][53][54][55][56][57][58][59] The wash out time duration is given in brackets. ...
... included in this review. 24,28,32,40,41,[46][47][48][49][50][51][52][53][54][55][56][57][58][59] The study population comprised at least 10 individuals/group in 12 studies, and fewer than 10 individuals/group in seven studies. ...
... More studies would be needed to establish the combined supplement of Bcaa with glutamine or taurine as an effective nutritional strategy in muscle damage induced by high-intense exercise and post-exercise recovery. Table ii exhibits the results from studies 24,28,32,40,41,[46][47][48][49][50][51][52][53][54][55][56][57][58][59] on the effect of Bcaa consumption on the above variables. The positive results were a decrease in the experimental group (vs. ...
Article
Introduction: Numerous sportspeople consume nutritional ergogenic aids, 0including branched chain amino acids (BCAA), considered to favor post-exercise muscle recovery. The purpose of this study was to assess the effect of BCAA on recovery from muscle damage produced by high-intensity exercise and muscle function. This allowed to define the optimal dosage regimen and consumption conditions taking into account the combination of BCAA with other products. Evidence acquisition: A systematic review of the scientific literature published over the past 15 years using the PubMed/MEDLINE, Scopus and Web of Science databases was carried out. Nineteen articles were selected. Evidence synthesis: The most optimal regimen for post-exercise muscle recovery and/or muscle function after high-intensity resistance exercise was 2-10 g BCAA/day (leucine: isoleucine: valine at 2:1:1), consumed as a supplement alone or combined with arginine and carbohydrates, 3 previous days before exercise, immediately before and after exercise, regardless of training level. This treatment can improve perceived muscle damage, fatigue, circumference of arm/leg, counter movement jump, maximum muscle strength and maximum voluntary contraction, and reduce creatine kinase and lactate dehydrogenase levels, mainly in young males. Conclusions: Intake of BCAA favors post-exercise muscle recovery and may improve muscle function. The present review can serve as a guidance for high intensity endurance athletes who need to reduce post-exercise muscle damage and maintain or improve muscle function, especially in training periods and competition events planned with short rest periods.
... Participants performed a CMJ on a mobile jump mat (Smart Jump, Fusion Sport, Australia) to assess maximal jumping height, and peak power output/body weight ratio (PPO/BW) (Rindom et al. 2016;Waldron et al. 2017). Participants were given three attempts interspaced by 1 min of recovery. ...
... Qualified personnel individually supervised each participant during test. The test-retest reliability of this procedure was 1.2% (Coefficient of variation) (Waldron et al. 2017). ...
... It is noteworthy that CK levels may be ambiguous for analyzing the impact of BCAA supplementation on muscle soreness, since a positive effect of BCAA was found on muscle soreness (Jackman et al. 2010;Waldron et al. 2017), even when CK levels were unchanged (Jackman et al. 2010;Shimomura et al. 2010) or higher (Waldron et al. 2017) in relation placebo. Moreover, a large interindividual variability is often observed in CK levels in response to muscle damage (Clarkson and Ebbeling 1988) and there is no correlation between the increase in CK and loss of muscle strength (Jackman et al. 2010). ...
Article
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The purpose of this study was to investigate the effects of BCAA supplementation on muscle recovery from resistance exercise (RE) in untrained young adults. Twenty-four young adults (24.0 ± 4.3 years old) were assigned to 1 of 2 groups (n = 12 per group): a placebo-supplement group or a BCAA-supplement group. The groups were supplemented for a period of 5 days. On day 1 and 3, both groups underwent a RE session involving two lower body exercises (hack squat and leg press) and then were evaluated for muscle recovery on the 3 subsequent moments after the RE session [30 min (day 3), 24 h (day 4), and 48 h (day 5)]. The following indicators of muscle recovery were assessed: number of repetitions, rating of perceived exertion in the last RE session, muscle soreness and countermovement jump (CMJ) during recovery period (30 min, 24 h, and 48 h after RE session). Number of repetitions remained unchanged over time (time, P > 0.05), while the rating of perceived exertion increased (time, P < 0.05) over 3 sets, with no difference between groups (group × time, P > 0.05). Muscle soreness increased (time, P < 0.05) and jumping weight decreased (time, P < 0.05) at 30 min post-exercise and then progressively returned to baseline at 24 and 48 h post-exercise, with no difference between groups (group × time, P > 0.05). The results indicate that BCAA supplementation does not improve muscle recovery from RE in untrained young adults.
... In the studies outlined in Chapters 5 and 6, participants were asked to maintain their normal diet and avoid the consumption of ergogenic supplementation throughout the course of the study. Indeed, there is evidence that protein (Buckley et al., 2010;Farup et al., 2014;Jackman, Witard, Jeukendrup & Tipton, 2010;Waldron et al., 2017) and ...
... Hyperaminoacidemia after protein ingestion stimulates muscle MPS that is thought to enhance recovery from resistance exercise (Buckley et al., 2010;Cockburn et al., 2010;Waldron et al., 2017). It is possible that protein supplementation induces a faster recovery of muscle function after muscle-damaging resistance exercise (Buckley et al., 2010;Cockburn, et al., 2008;Farup et al., 2014;Jackman, Witard, Jeukendrup & Tipton, 2010;Waldron et al., 2017), despite a review by Pasiakos and colleagues disputing this claim (Pasiakos, Lieberman & McLellan, 2014). ...
... Hyperaminoacidemia after protein ingestion stimulates muscle MPS that is thought to enhance recovery from resistance exercise (Buckley et al., 2010;Cockburn et al., 2010;Waldron et al., 2017). It is possible that protein supplementation induces a faster recovery of muscle function after muscle-damaging resistance exercise (Buckley et al., 2010;Cockburn, et al., 2008;Farup et al., 2014;Jackman, Witard, Jeukendrup & Tipton, 2010;Waldron et al., 2017), despite a review by Pasiakos and colleagues disputing this claim (Pasiakos, Lieberman & McLellan, 2014). However, the different study designs and large variability in indirect markers might contribute to the equivocal findings (Pasiakos et al., 2014). ...
Thesis
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Little is known about the muscle function capabilities of trained middle-aged males and how they differ to younger counterparts. Accordingly, the overall aim of the research documented in this thesis was to compare the acute muscle function responses to resistance exercise in middle-aged and young resistance trained males. The first study (Chapter 3) examined the intra- and inter-day reliability of an ecologically valid device (FitroDyne rotary encoder) for measuring upper and lower-body muscle function during three popular multi-jointed resistance training exercises (bench press, squat, and bent-over-row), and confirmed that it was capable of detecting moderate changes in muscle function across a range of submaximal loads. In the second study (Chapter 4) the load-velocity and load-power relationships were investigated during the same exercises among 20 young (age 21.0 ± 1.6 y) and 20 middle-aged (age 42.6 ± 6.7 y) resistance trained males, and it emerged that, despite their regular training, the middle-aged males were unable to achieve velocities at low external loads and peak powers at all external loads as high as the young males across a range of external resistances. Study three (Chapter 5) proceeded to compare the internal (heart rate (HR), OMNI-ratings of perceived exertion (RPE) and sRPE) and external (peak velocity and power and volume load) loads experienced during high volume squatting exercise, and the fatigue responses among nine young (age 22.3 ± 1.7 years) and nine middle-aged (age 39.9 ± 6.2 years) resistance trained males. The findings highlighted that internal, but not certain markers of external (peak power and volume load), load responses can be monitored during exercise in a like manner between these age groups. Moreover, compared to young resistance trained males, middle-aged males can expect greater decrements in peak power after lower-limb resistance exercise. In the final study (Chapter 6), the time-course of recovery in nine trained young (age 22.3 ± 1.7 years) and nine trained (39.9 ± 6.2 years) and nine untrained (44.4 ± 6.3 years) middle-aged males after high volume lower-body resistance (muscle damaging) exercise was investigated. Of practical importance, it emerged that compared to the young males, the trained middle-aged males experienced greater symptoms of muscle damage and an impaired recovery profile, the implication of which is the need for trained middle-aged males to adopt strategies to enhance their recovery. Furthermore, both middle-aged groups experienced similar symptoms of muscle-damage, albeit the untrained group demonstrated greater losses in peak power at low and high external loads. For the first time, the current research has determined that middle-aged males, despite regular resistance training, are subject to losses in peak velocity and power output across a range external loads, compared to young males. When undergoing lower-body resistance training to ameliorate these decrements, applied practitioners can use internal load markers and peak velocity, but not peak power or volume load, to monitor trained young and middle-aged males alike. Furthermore, the muscle damage response (24 to 72 h), and losses in peak power (0 to 72 h), after lower-body resistance exercise are greater in trained middle-aged than young males. Consequently, future research should seek to corroborate these observations in upper-body exercise and determine the effectiveness of strategies (e.g. nutritional intake) to enhance recovery in middle-aged males.
... Table 2 shows the data on all the retrieved trials in this systematic review. In total, nine studies employed a parallel study design (41,48,67,71,(73)(74)(75)(76)(77), while seven studies used a cross-over design (52,65,66,(68)(69)(70)72). The majority of the studies were conducted on male subjects. In addition, six trials investigated the effects of BCAA acute supplementation (48,65,72,(74)(75)(76). ...
... In total, nine studies employed a parallel study design (41,48,67,71,(73)(74)(75)(76)(77), while seven studies used a cross-over design (52,65,66,(68)(69)(70)72). The majority of the studies were conducted on male subjects. In addition, six trials investigated the effects of BCAA acute supplementation (48,65,72,(74)(75)(76). The duration of intervention in seven studies was less than or equal to one week (41,52,66,68,70,73,77), while in three trials, the duration was longer than one week (67,69,71). ...
... In total, 12 effect sizes were assessed in the metaanalysis in order to determine the effect of BCAA supplementation on DOMS [8,9,11,42,43,47,48,[50][51][52]. Two studies provided two different effect sizes [8,11]. ...
Article
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This meta-analysis and systematic review aimed to attain specific data on the effect of branched-chain amino acids (BCAAs) administration on muscle injuries and the indices of delayed-onset muscle soreness (DOMS) after exercise. Literature search was performed in databases such as Scopus, ISI, Web of Science, Scientific Information Database (SID), Cochrane Controlled Register of Trials (CENTRAL), and Cochrane library for the articles published until January 2017. The clinical trials examining the effects of BCAA administration on athletes were considered eligible. In total, 42 studies were evaluated in terms of eligibility, 26 of which were excluded from the meta-analysis. According to the meta-analysis, BCAA supplementation significantly reduced the levels of creatine kinase 24 hours post-exercise (mean difference: -129.55 [95% CI: -237.02--22.07] IU/l; P=0.018). However, BCAA administration could not decrease lactate dehydrogenase promptly (mean difference: -10.11 [95% CI: -21.76-1.53] IU/l; P=0.08) 24 hours post-exercise (mean difference: -14.66 [95% CI: -32.16-2.83] IU/l; P=0.10). Therefore, it could be concluded that BCAA consumption is inversely associated with DOMS at 24 hours (standardized mean difference [SMD] =-0.43 [95% CI: -0.71--0.16]; P=0.002), 48 hours (SMD=-0.55 [95% CI: -0.81--0.29]; P
... First, the additional effect of β-alanine supplementation on intracellular buffer capacity (i.e., reducing acidosis) may be insufficient to overcome the negative impact of RE on muscle function during the recovery period. Highintensity RE is naturally associated with pronounced microinjury (as indicated by the increase in CK levels) (da Silva et al. 2017;Waldron et al. 2017;Pareja-Blanco et al. 2018) and delayed-onset muscle soreness (Flores et al. 2011;da Silva et al. 2017;Waldron et al. 2017), resulting in a marked decline in muscle function (e.g., peak torque and isometric strength) (Flores et al. 2011;Ferreira et al. 2017;Waldron et al. 2017). This impairment on muscle function may be exacerbated when exercise is performed until muscle failure (Morán-Navarro et al. 2017;Pareja-Blanco et al. 2018), and generally requires a period of 48-72 h for complete recovery (ACSM 2009). ...
... First, the additional effect of β-alanine supplementation on intracellular buffer capacity (i.e., reducing acidosis) may be insufficient to overcome the negative impact of RE on muscle function during the recovery period. Highintensity RE is naturally associated with pronounced microinjury (as indicated by the increase in CK levels) (da Silva et al. 2017;Waldron et al. 2017;Pareja-Blanco et al. 2018) and delayed-onset muscle soreness (Flores et al. 2011;da Silva et al. 2017;Waldron et al. 2017), resulting in a marked decline in muscle function (e.g., peak torque and isometric strength) (Flores et al. 2011;Ferreira et al. 2017;Waldron et al. 2017). This impairment on muscle function may be exacerbated when exercise is performed until muscle failure (Morán-Navarro et al. 2017;Pareja-Blanco et al. 2018), and generally requires a period of 48-72 h for complete recovery (ACSM 2009). ...
... First, the additional effect of β-alanine supplementation on intracellular buffer capacity (i.e., reducing acidosis) may be insufficient to overcome the negative impact of RE on muscle function during the recovery period. Highintensity RE is naturally associated with pronounced microinjury (as indicated by the increase in CK levels) (da Silva et al. 2017;Waldron et al. 2017;Pareja-Blanco et al. 2018) and delayed-onset muscle soreness (Flores et al. 2011;da Silva et al. 2017;Waldron et al. 2017), resulting in a marked decline in muscle function (e.g., peak torque and isometric strength) (Flores et al. 2011;Ferreira et al. 2017;Waldron et al. 2017). This impairment on muscle function may be exacerbated when exercise is performed until muscle failure (Morán-Navarro et al. 2017;Pareja-Blanco et al. 2018), and generally requires a period of 48-72 h for complete recovery (ACSM 2009). ...
Article
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β-alanine supplementation has been shown to increase muscle carnosine levels and exercise performance. However, its effects on muscle recovery from resistance exercise (RE) remains unknown. The purpose of this study was to investigate the effects of β-alanine supplementation on muscle function during recovery from a single session of high-intensity RE. Twenty-four untrained young adults (22.1 ± 4.6 years old) were assigned to 1 of 2 groups (N = 12 per group): a placebo-supplement group (4.8 g/day) or an β-alanine-supplement group (4.8 g/day). The groups completed a single session of high-intensity RE after 28 days of supplementation and were then evaluated for muscle function on the 3 subsequent days (at 24, 48, and 72 h postexercise) to assess the time course of muscle recovery. The following indicators of muscle recovery were assessed: number of repetitions until failure, rating of perceived exertion, muscle soreness, and blood levels of creatine kinase (CK). Number of repetitions until failure increased from 24 h to 48 h and 72 h of recovery (time, P < 0.01), with no difference between groups. There was a significant increase in rating of perceived exertion among the sets during the RE session (time, P < 0.01), with no difference between the groups. No difference was observed over time and between groups in rating of perceived exertion in the functional tests during recovery period. Blood CK levels and muscle soreness increased at 24 h postexercise and then progressively declined at 48 and 72 h postexercise, respectively (time, P < 0.05), with no difference between groups. In conclusion, our data indicate that β-alanine supplementation does not improve muscle recovery following a high-intensity RE session in untrained young adults.
... Whist leucine is an effective recovery supplement when co-ingested with other BCAAs (Howatson et al. 2012;Waldron et al. 2017), it is possible that leucine is more effective for cellular recovery when it is not mixed with BCAA solutions. This may be due to the reported competition between leucine, isoleucine and valine for cellular transport (Cynober 2002). ...
... For example, Kirby et al. (2012) reported an improvement in recovery of isometric strength (~ 5%) after muscle damage, using a short-term (beginning 30 min prior 0074o exercise) leucine supplementation regime, similar in timing to the current study. In combination with other BCAAs, leucine has been repeatedly shown to increase the rate of recovery from muscle-damaging exercise (Howatson et al. 2012;Jackman et al. 2010;Matsumoto et al. 2009;Waldron et al. 2017). While some have reported no change in muscle damage markers following BCAA supplementation (Kephart et al. 2016;Ra et al. 2013), this could be related to the relatively small doses (~ 3-5 g) provided compared to other studies (15-20 g; Waldron et al. 2017;Howatson et al. 2012). ...
... In combination with other BCAAs, leucine has been repeatedly shown to increase the rate of recovery from muscle-damaging exercise (Howatson et al. 2012;Jackman et al. 2010;Matsumoto et al. 2009;Waldron et al. 2017). While some have reported no change in muscle damage markers following BCAA supplementation (Kephart et al. 2016;Ra et al. 2013), this could be related to the relatively small doses (~ 3-5 g) provided compared to other studies (15-20 g; Waldron et al. 2017;Howatson et al. 2012). Whilst there are putative roles for all BCAAs in muscle protein synthesis (Blomstrand et al. 2006), leucine is known to confer the most potent anabolic signalling effects, whereas isoleucine and valine have negligible contributions (Atherton et al. 2010). ...
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This study investigated the effects of leucine or leucine + glutamine supplementation on recovery from eccentric exercise. In a double-blind independent groups design, 23 men were randomly assigned to a leucine (0.087 g/kg; n = 8), leucine + glutamine (0.087 g/kg + glutamine 0.3 g/kg; n = 8) or placebo (0.3 g/kg maltodextrin; n = 7) group. Participants performed 5 sets of drop jumps, with each set comprising 20 repetitions. Isometric knee-extensor strength, counter-movement jump (CMJ) height, delayed-onset muscle soreness (DOMS) and creatine kinase (CK) were measured at baseline, 1, 24, 48 h and 72 h post-exercise. There was a time × group interaction for isometric strength, CMJ and CK (P < 0.05), with differences between the leucine + glutamine and placebo group at 48 h and 72 h for strength (P = 0.013; d = 1.43 and P < 0.001; d = 2.06), CMJ (P = 0.008; d = 0.87 and P = 0.019; d = 1.17) and CK at 24 h (P = 0.012; d = 0.54) and 48 h (P = 0.010; d = 1.37). The leucine group produced higher strength at 72 h compared to placebo (P = 0.007; d = 1.65) and lower CK at 24 h (P = 0.039; d = 0.63) and 48 h (P = 0.022; d = 1.03). Oral leucine or leucine + glutamine increased the rate of recovery compared to placebo after eccentric exercise. These findings highlight potential benefits of co-ingesting these amino acids to ameliorate recovery.
... The exogenous amino acids BCAAs which include: valine, leucine and isoleucine, took next place in terms of the popularity of use by the women exercising in fitness clubs but not used at all in the Control Group. BCAAs are key amino acids that stimulate protein synthesis Kerksick et al., 2018;Waldron et al., 2017;Van Dusseldorp et al., 2018). Generally, supplementation with Essential Amino Acids (EAAs), which also includes BCAAs, should be at levels of 3-6 g of amino acids after exercise. ...
... Consumption of BCAA alone (6-10 g per hour) before, during and after exercise is recommended as safe and effective for athletes. The recommendations for this type of preparation are related to the fact that these amino acids act as an energy substrate, are easily digestible, help build muscle mass, contribute to the inhibition of muscle catabolism, show strong anabolic properties, delay the occurrence of fatigue after long and intense training, and have a positive effect on the immune system Kerksick et al., 2018;Waldron et al., 2017;Van Dusseldorp et al., 2018). ...
... In fact, evidence over the last 2 decades suggest that oral supplements of BCAA may exhibit prophylactic effects to ameliorate the signs and symptoms of EIMD. For example, several studies have reported that supplementation of BCAA reduced the level of muscle damage biomarkers (e.g., CK) (Coombes and McNaughton 2000;Greer et al. 2007;Howatson et al. 2012;Matsumoto et al. 2009;Osmond et al. 2019;Ra et al. 2013a;Sharp and Pearson 2010;Shimomura et al. 2010) and DOMS (Howatson et al. 2012;Jackman et al. 2010;Leahy and Pintauro 2013;Matsumoto et al. 2009;Ra et al. 2013a;Reule et al. 2017;Shimomura et al. 2006), while improving muscular performance (e.g., isometric force) (Howatson et al. 2012;Osmond et al. 2019;Reule et al. 2017;VanDusseldorp et al. 2018;Greer et al. 2007;Waldron et al. 2017) for 24-48 hours post-exercise. However, BCAA supplementation has also been reported to have no impact on outcome measures associated with EIMD (Foure et al. 2016;Kephart et al. 2016;Lin et al. 2017;Mohamad-Panahi et al. 2013;Sheikholeslami-Vatani and Ahmadi 2016). ...
... The muscle damage markers became significantly lower for the BCAA than the PLA conditions when several studies (Foure et al. 2016;Gervasi et al. 2020;Jackman et al. 2010;Kephart et al. 2016;Lin et al. 2017;Sheikholeslami-Vatani and Ahmadi 2016;Shimomura et al. 2010;Waldron et al. 2017) were individually removed at 24 hours post-exercise. However, the meta-analysis for muscle damage markers remained similar when studies were individually removed at 48 hours post-exercise. ...
Article
This systematic review and meta-analysis determined whether the ergogenic effects of branched-chain amino acids (BCAA) ameliorated markers of muscle damage and performance following strenuous exercise. In total, 25 studies were included, consisting of 479 participants (age 24.3 ± 8.3 years, height 1.73 ± 0.06 m, body mass 70.8 ± 9.5 kg, females 26.3%). These studies were rated as fair to excellent following the PEDro scale. The outcome measures were compared between the BCAA and placebo conditions at 24 and 48 hours following muscle-damaging exercises, using standardised mean differences and associated p-values via forest plots. Our meta-analysis demonstrated significantly lower levels of indirect muscle damage markers (creatine kinase, lactate dehydrogenase and myoglobin) at 48 hours post-exercise (standardised mean difference [SMD] = −0.41; p < 0.05) for the BCAA than placebo conditions, whilst muscle soreness was significant at 24 hours post-exercise (SMD = −0.28 ≤ d ≤ −0.61; p < 0.05) and 48 hours post-exercise (SMD = −0.41 ≤ d≤ −0.92; p < 0.01). However, no significant differences were identified between the BCAA and placebo conditions for muscle performance at 24 or 48 hours post-exercise (SMD = 0.08 ≤ d ≤ 0.21; p > 0.05). Overall, BCAA reduced the level of muscle damage biomarkers and muscle soreness following muscle-damaging exercises. However, the potential benefits of BCAA for muscle performance recovery is questionable and warrants further investigation to determine the practicality of BCAA for ameliorating muscle damage symptoms in diverse populations. PROSPERO registration number: CRD42020191248. Novelty: BCAA reduces the level of creatine kinase and muscle soreness following strenuous exercise with a dose–response relationship. BCAA does not accelerate recovery for muscle performance.
... For instance, considering low-to-moderate EIMD, a low frequency (i.e., less than 2 intakes per day) and a low daily amount of BCAAs intake (i.e., less than 200 mg kg −1 day −1 ) during a moderate supplementation duration (i.e., between 4 and 10 days) was not enough to produce benefits on EIMD indirect markers [37]. Moreover, no significant positive effects on outcomes has been found when supplementation combined a high frequency and a high daily amount over a short period of time [36,41]. A long BCAAs supplementation period (>10 days) appears necessary if one is expecting beneficial effects. ...
... et al. (2016) [32] Significant increase in plasma CK activity at D3 and D4 -Greer et al. (2007) [34] Significant increase in CK (from H4 to D2) and LDH (at H4) Yes Howatson et al. (2012) [35] Significant increase in CK from D1 to D3 Yes Jackman et al. (2010) [36] Significant increase in CK (from H8 to D3) and myoglobin (at H1, H8 and D3) -Kephart et al. (2016) [37] Significant increase in myoglobin -Matsumoto et al. (2007) [38] Significant increase in CK and LDH at POST Yes Ra et al. (2013) [39] Significant increase in CK and LDH at D3 and D4 -Shimomura et al. (2010) [40] No significant change in CK and LDH on the three days post-exercise -Waldron et al. (2017)[41] No change in CK on the two days post-exercise -LDH: lactate dehydrogenase, CK: creatine kinase, POST: immediately after the damaging exercise, H: hour (e.g., H4: four hours after the end of the damaging exercise), D: day (e.g., D4: four days after the damaging exercise), MVC: maximal voluntary contraction force, CMJ: counter movement jump, SSPT: seated shot-put throw. ...
Article
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Amino acids and more precisely, branched-chain amino acids (BCAAs), are usually consumed as nutritional supplements by many athletes and people involved in regular and moderate physical activities regardless of their practice level. BCAAs have been initially shown to increase muscle mass and have also been implicated in the limitation of structural and metabolic alterations associated with exercise damage. This systematic review provides a comprehensive analysis of the literature regarding the beneficial effects of BCAAs supplementation within the context of exercise-induced muscle damage or muscle injury. The potential benefit of a BCAAs supplementation was also analyzed according to the supplementation strategy—amount of BCAAs, frequency and duration of the supplementation—and the extent of muscle damage. The review protocol was registered prospectively with Prospective Register for Systematic Reviews (registration number CRD42017073006) and followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. Literature search was performed from the date of commencement until August 2017 using four online databases (Medline, Cochrane library, Web of science and ScienceDirect). Original research articles: (i) written in English; (ii) describing experiments performed in Humans who received at least one oral BCAAs supplementation composed of leucine, isoleucine and valine mixture only as a nutritional strategy and (iii) reporting a follow-up of at least one day after exercise-induced muscle damage, were included in the systematic review analysis. Quality assessment was undertaken independently using the Quality Criteria Checklist for Primary Research. Changes in indirect markers of muscle damage were considered as primary outcome measures. Secondary outcome measures were the extent of change in indirect markers of muscle damage. In total, 11 studies were included in the analysis. A high heterogeneity was found regarding the different outcomes of these studies. The risk of bias was moderate considering the quality ratings were positive for six and neutral for three. Although a small number of studies were included, BCAAs supplementation can be efficacious on outcomes of exercise-induced muscle damage, as long as the extent of muscle damage was low-to-moderate, the supplementation strategy combined a high daily BCAAs intake (>200 mg kg−1 day−1) for a long period of time (>10 days); it was especially effective if taken prior to the damaging exercise.
... BCAAs are the most abundant EAAs and participate in protein synthesis and in recovery from high-intensity exercise [15,16]. Leu promotes slow-twitch skeletal muscle fiber expression in porcine skeletal muscle satellite cells. ...
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Skeletal muscle is a heterogeneous tissue composed of a variety of functionally different fiber types. Slow-twitch type I muscle fibers are rich with mitochondria, and mitochondrial biogenesis promotes a shift towards more slow fibers. Leucine, a branched-chain amino acid (BCAA), regulates slow-twitch muscle fiber expression and mitochondrial function. The BCAA content is increased in porcine whole-blood protein hydrolysates (PWBPH) but the effect of PWBPH on muscle fiber type conversion is unknown. Supplementation with PWBPH (250 and 500 mg/kg for 5 weeks) increased time to exhaustion in the forced swimming test and the mass of the quadriceps femoris muscle but decreased the levels of blood markers of exercise-induced fatigue. PWBPH also promoted fast-twitch to slow-twitch muscle fiber conversion, elevated the levels of mitochondrial biogenesis markers (SIRT1, p-AMPK, PGC-1α, NRF1 and TFAM) and increased succinate dehydrogenase and malate dehydrogenase activities in ICR mice. Similarly, PWBPH induced markers of slow-twitch muscle fibers and mitochondrial biogenesis in C2C12 myotubes. Moreover, AMPK and SIRT1 inhibition blocked the PWBPH-induced muscle fiber type conversion in C2C12 myotubes. These results indicate that PWBPH enhances exercise performance by promoting slow-twitch muscle fiber expression and mitochondrial function via the AMPK/SIRT1 signaling pathway.
... Participants performed countermovement jumps on a mobile jump mat (Smart Jump, Fusion Sport, Australia) to assess normalized (PPO/body weight) (Estoche et al., 2019;Rindom et al., 2016;Waldron et al., 2017) of the lower body (knee extensors and triceps surae). A 5-min warm-up for the lower body muscles was performed, which consisted of muscle activation (stationary walking for 1 min) and static stretching exercises for the knee extensors and triceps surae muscles. ...
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The purpose of this study was to investigate the effects of supplementation of whey protein (WP) versus leucine-matched collagen peptides (CP) on muscle thickness (MT) and performance after a resistance training (RT) program in young adults. Twenty-two healthy untrained participants were randomly assigned to either a WP (n = 11) or leucine-matched CP (n = 11) group and then submitted to a supervised 10-wk RT program (3 d·wk-1). The groups were supplemented with an equivalent amount of WP (35 g, containing 3.0 g of leucine) and CP (35 g, containing 1.0 g of leucine and 2.0 g of free leucine) during the intervention period (after each workout and in the evening on non-training days). MT of the vastus lateralis and biceps brachii, isokinetic peak torque (PT) and mean power output (MPO) of the elbow flexors, and peak power output (PPO) of the lower body were assessed before and after the RT program. WP group experienced a greater (interaction P < 0.05) increase in the vastus lateralis (effect size, WP: 0.68 vs. CP: 0.38; ∆%, WP: 8.4 ± 2.5 vs. CP: 5.6 ± 2.6%) and biceps brachii MT (effect size, WP: 0.61 vs. CP: 0.35; ∆%, WP: 10.1 ± 3.8 vs. CP: 6.0 ± 3.2%), with a similar increase in muscle performance (PT, MPO, and PPO) between groups (time p < 0.05). Supplementation with WP was superior to leucine content-matched CP supplementation in increasing muscle size, but not strength and power, after a 10-wk RT program in young adults.
... Studies have also shown beneficial effects of BCAA supplementation in several sarcopenic cohorts, including the elderly and patients with chronic liver disease comprising those with cirrhosis [53][54][55][56][57][58]. Furthermore, BCAA enhances muscle strength and mass [54,[59][60][61][62]. A well-known risk factor for worse sepsis outcomes is sarcopenia [63][64][65]. ...
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Sepsis biomarkers and potential therapeutic targets are urgently needed. With proton nuclear magnetic resonance (1 H NMR) spectroscopy, several metabolites can be assessed simultaneously. Fifty-three adult medical ICU sepsis patients and 25 ICU controls without sepsis were prospectively enrolled. 1 H NMR differences between groups and associations with 28-day and ICU mortality were investigated. In multivariate metabolomic analyses, we found separate clustering of ICU controls and sepsis patients, as well as septic shock survivors and non-survivors. Lipoproteins were significantly different between sepsis and control patients. Levels of the branched-chain amino acids (BCAA) valine (median 43.3 [29.0-53.7] vs. 64.3 [47.7-72.3] normalized signal intensity units; p = 0.005), leucine (57.0 [38.4-71.0] vs. 73.0 [54.3-86.3]; p = 0.034) and isoleucine (15.2 [10.9-21.6] vs. 17.9 [16.1-24.4]; p = 0.048) were lower in patients with septic shock compared to those without. Similarly , BCAA were lower in ICU non-survivors compared to survivors, and BCAA were good dis-criminators for ICU and 28-day mortality. In uni-and multivariable logistic regression analyses, higher BCAA levels were associated with decreased ICU-and 28-day mortality. In conclusion, metabolomics using 1 H NMR spectroscopy showed encouraging potential for personalized medicine in sepsis. BCAA was significantly lower in sepsis non-survivors and may be used as early bi-omarkers for outcome prediction.
... Oleh karena itu, kemungkinan CK tidak dapat menjadi satu-satunya marker yang ideal untuk indikator kerusakan otot, dan membutuhkan beberapa marker tambahan seperti LDH dan troponin. 14 ...
Article
Background: Sensation in the form of pain, edema, and stiffness that increases 24-48 hours after high-intensity training, especially eccentric exercises is called Delayed Onset Muscle Soreness (DOMS). One method to accelerate the recovery process and reduce the pain caused by DOMS is with Branched-Chain Amino Acid (BCAA) supplementation. However, until now, there has been limited research that proves the difference in the effectiveness of supplementation time between before and after exercise. Objectives: The aim of this research was to determine the difference in the effectiveness of BCAA supplementation time on DOMS.Methods: This research was an experimental research. A posttest only control group design approach was carried out to measure the effectiveness of supplementation on DOMS as measured by VAS at 24 hours after exercise. A pre and post control group design approach was carried out to measure the effectiveness of supplementation on the alteration in Range of Motion (ROM) as measured by the modified Lower Extremity Functional Scale (LEFS) questionnaire before exercise and 24 hours after exercise. The subjects were classified into 3 groups, namely the control group, 30 minutes before exercise supplementation, and 1 hour after exercise supplementation. Data were analyzed by one way ANOVA and Kruskall Wallis tests. Results Total sample in this study was 30 people. The result of oneway ANOVA test for differences in the effectiveness of BCAA supplementation on VAS was p<0.001. The result of post hoc test between the control and before and after exercise supplementation group was p<0.001, while between the before and after supplementation group was p=0.113. The result of Kruskall Wallis test to measure the effectiveness of supplementation on the alteration (Δ) in LEFS was p=0.336Conclusion: There was no significant difference in the level of pain between the before and after BCAA supplemented group. However, there were significant differences in the level of pain in both of the before and after supplementation group with the control group. There was no significant differences in the alteration of ROM between the three groups
... More men than women in our study used DSs that enhance their performance during PA and improve their body image and muscle bulk; these included branched-chain amino acids, protein bars and powder, caffeine, energy drinks, and creatine. [46][47][48][49][50] Calcium and vitamin D were used more frequently by women; this can be explained by their lower exposure to the sun, which makes them prone to a vitamin D deficiency. 51 Women used iron supplements 4 times more frequently than men; iron loss through menstruation can explain this finding, 30 and a similar conclusion was reached by Barnes et al. 36 Although only 6% of the women were married, 10% (or 22.6% of those using DSs) took folic acid supplements. ...
Article
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Oral dietary supplements (DSs) include vitamins, minerals, amino acids, energy drinks, and herbal products. The use of DSs is increasing and their manufacturers promote their benefits. Studies have validated some of these benefits, but have also indicated that some DSs can have adverse effects, especially if used without the appropriate supervision. Little information on DS use among Saudis is available. This study assessed the use of dietary supplements among male and female university students with the goal of educating the community about DSs and the dangers associated with their misuse. Online and paper validated questionnaires were administered to King Abdulaziz University (KAU) students between September 2019 and January 2020. The responses were collected and analyzed statistically. Of the 954 KAU students who completed the survey, one-third used DSs (42.9% women vs 25.7% men). Of these, 51.7% believed that DSs are essential for health, 41.7% classified them as both food and drugs, 67.2% were aware that DSs could not replace a healthy diet, and 25.8% were aware of their potentially harmful effects. Multivitamins and minerals were the most used DSs. DS awareness among KAU students is limited. Additional health education is necessary to assist students in their selection of the most suitable DSs.
... Given the findings, the authors noted that this finding holds questionable applicability to the majority of individuals who engage in dynamic movements and also questioned whether effects would hold true if individuals consumed a diet consisting of adequate protein. Waldron et al. (2017) similarly observed a preservation in isometric strength as well as a small benefit to preserving countermovement jump performance compared with placebo. Alternatively, Smith et al. (2018) found no improvements in upper body muscular strength involving bench press and rowing exercises among participants supplementing with BCAA. ...
Article
Branched-chain amino acids (BCAA) are one of the most popular sports supplements, marketed under the premise that they enhance muscular adaptations. Despite their prevalent consumption among athletes and the general public, the efficacy of BCAA has been an ongoing source of controversy in the sports nutrition field. Early support for BCAA supplementation was derived from extrapolation of mechanistic data on their role in muscle protein metabolism. Of the three BCAA, leucine has received the most attention because of its ability to stimulate the initial acute anabolic response. However, a substantial body of both acute and longitudinal research has now accumulated on the topic, affording the ability to scrutinize the effects of BCAA and leucine from a practical standpoint. This article aims to critically review the current literature and draw evidence-based conclusions about the putative benefits of BCAA or leucine supplementation on muscle strength and hypertrophy as well as illuminate gaps in the literature that warrant future study.
... BCAA can be used in sports branches that require immediate reactions. Waldron (2017) examined the effect of BCAA intake before and after exercise (70%, 10 * 6 sets of squats * 3 days) on CK and DOMS. According to the findings, CK and DOMS showed similar increases in both groups. ...
... In contrast to group A (involving oxidative phosphorylation), group R mainly focused on amino acid metabolism, such as histidine metabolism, arginine biosynthesis and branched-chain amino acid (BCAA) metabolism, which promoted protein renewal and led to muscle hypertrophy [61][62][63][64]. In addition, compared with the control, enriched pathways of autonomous climbing are related to aerobic oxidation and amino acid metabolism, consistent with our molecular experiment results, implying increases in mitochondrial function and protein synthesis in mouse muscle [12,61,65,66]. Tyrosine metabolism is related to ketogenesis and blood glucose homeostasis function in ketogenic diets Heat map for the differentially expressed metabolites belonging to the enriched pathway. ...
Article
Aims To assess the effects of three specific exercise training modes, aerobic exercise (A), resistance training (R) and autonomous climbing (AC), aimed at proposing a cross-training method, on improving the physical, molecular and metabolic characteristics of mice without many side effects. Materials and methods Seven-week-old male mice were randomly divided into four groups: control (C), aerobic exercise (A), resistance training (R), and autonomous climbing (AC) groups. Physical changes in mice were tracked and analysed to explore the similarities and differences of these three exercise modes. Histochemistry, quantitative real-time PCR (RT-PCR), western blot (WB) and metabolomics analysis were performed to identify the underlying relationships among the three training modes. Key findings Mice in the AC group showed better body weight control, glucose and energy homeostasis. Molecular markers of myogenesis, hypertrophy, antidegradation and mitochondrial function were highly expressed in the muscle of mice after autonomous climbing. The serum metabolomics landscape and enriched pathway comparison indicated that the aerobic oxidation pathway (pentose phosphate pathway, galactose metabolism and fatty acid degradation) and amino acid metabolism pathway (tyrosine, arginine and proline metabolism) were significantly enriched in group AC, suggesting an increased muscle mitochondrial function and protein balance ability of mice after autonomous climbing. Significance We propose a new exercise mode, autonomous climbing, as a convenient but effective training method that combines the beneficial effects of aerobic exercise and resistance training.
... L'ensemble de nos données moléculaires ont montré que contrairement aux traitements par oxygénation ou par stimulation électrique, l'incorporation de BCAAs au milieu de différenciation des cellules musculaires C2C12 sous hypoxie (4% O2) n'a engendré que peu de variation sur les protéines de la voie Akt / mTOR, et aucun changement positif sur les différents facteurs de la protéolyse considérés dans notre protocole (Figure 60). Malgré un certain nombre d'études sur la supplémentation en acides aminés dans le muscle squelettique, on ignore si l'absorption cellulaire et/ou l'action des acides aminés sont altérées dans la cellule musculaire en hypoxie (Engelen et al., 2007 ;Jewell et al., 2013 ;Waldron et al 2017). ...
Thesis
Introduction et : ’exposition chronique à une hypoxie (diminution du taux d’oxygène) sévère engendre des effets délétères sur le système musculaire, entrainant des conséquences néfastes sur la masse musculaire squelettique. L'hypoxie provoque un déséquilibre de l'homéostasie protéique (balance entre anabolisme et catabolisme), en diminuant la synthèse des protéines (principalement régulée par la voie PI3K-Akt-mTOR) tout en augmentant la dégradation des protéines (principalement par autophagie et dégradation protéasomique). En revanche, les stimulations mécaniques (activité physique) et la supplémentation nutritionnelle, en particulier les acides aminés essentiel branché (BCAA), induisent l'activation de la voie mTOR tout en inhibant les voies cataboliques du muscles squelettiques chez l'homme, l’animal et cellules musculaires misent en culture. Sur un modèle in vitro de cellule musculaire squelettique, nous avons essayé de déterminer si la combinaison de la stimulation mécanique, la supplémentation nutritionnelle et une période de réoxygénation post-stimulation pourrait inverser les effets délétères de l'hypoxie sur l'homéostasie protéique.Protocole expérimentalPour vérifier notre hypothèse, nous avons utilisé un modèle de cellule musculaire squelettique en culture (C2C12). Après quatre jours de différenciation les myotubes C2C12 ont été placés dans une chambre hypoxique à 4% de O2 pendant 24h. Á la suite de cette période d’hypoxie, un programme de stimulation électrique a été appliquée aux cellules musculaires en utilisant un générateur d'impulsions électriques. Á la fin de la stimulation électrique, les myotubes ont tout d'abord été supplémentés avec des acides aminés essentiel branché (BCAA: mélange de leucine, d'isoleucine et de valine ajoutés à un milieu de culture), puis placés pendant 2 heures dans un environnement de normoxie (21% O2) (correspondant à la période de réoxygénation).RésultatsAprès 24 heures d'hypoxie, l'analyse morphologique des myotubes montre une diminution significative de leur diamètre, traduisant l'activation des voies de dégradation des protéines aux dépens des voies de synthèse des protéines. Appliqué séparément, chaque traitement a peu d’effet sur la voie mTOR et la morphologie des myotubes. Alors que, la combinaison de la stimulation électrique, de la supplémentation en BCAA et de la réoxygénation conduit à une augmentation de la phosphorylation de protéines clés impliquées dans la voie de synthèse des protéines (Akt, mTOR, p70S6K, GSK-3β), reflétant ainsi leur état d'activation. De plus, l'analyse morphologique montre une augmentation significative du diamètre du myotube et de l'indice de fusion (reflétant l'état de différenciation), signe de la présence d'une hypertrophie musculaire.Conclusion Nos résultats suggèrent que la voie mTOR (l’une des voies principales de l’anabolisme) répond à une combinaison de stimulation électrique, de supplémentation en nutriments et de réoxygénation par phosphorylation de régulateurs clés de la synthèse des protéines, pouvant ainsi inverser la perte de protéines induite par l'hypoxie.
... For example, L-carnitine supplementation was reported to improve muscle soreness and prevent CK elevation after training sessions [149][150][151]. Similar effects were also observed after creatine supplementation [152] and branched-chain amino acids [153][154][155] (Table 6). Table 6. ...
Article
Acute and chronic physical exercises may enhance the development of statin-related myopathy. In this context, the recent (2019) guidelines of the European Society of Cardiology (ESC) and the European Atherosclerosis Society (EAS) for the management of dyslipidemias recommend that, although individuals with dyslipidemia should be advised to engage in regular moderate physical exercise (for at least 30 min daily), physicians should be alerted with regard to myopathy and creatine kinase (CK) elevation in statin-treated sport athletes. However it is worth emphasizing that abovementioned guidelines, previous and recent ESC/EAS consensus papers on adverse effects of statin therapy as well as other previous attempts on this issue, including the ones from the International Lipid Expert Panel (ILEP), give only general recommendations on how to manage patients requiring statin therapy on regular exercises. Therefore, these guidelines in the form of the Position Paper are the first such an attempt to summary existing, often scarce knowledge, and to present this important issue in the form of step-by-step practical recommendations. It is critically important as we might observe more and more individuals on regular exercises/athletes requiring statin therapy due to their cardiovascular risk.
... The composition of the protein supplement also plays an important role in muscle hypertrophy. Shimomura et al. 13 and Waldron et al. 32 reported that the quantity of BCAA required to maximize muscle function, is over 5 g and the ratio of Leu:Ile:Val is 2:1:1. Leucine especially plays a critical role in muscle synthesis via mechanisms involving the mammalian target of rapamycin (mTOR) signaling pathway, which contributes to muscle protein synthesis in human skeletal muscle 33 . ...
Article
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Purpose: The composition of protein supplements, the consumption timing immedi¬ately before and after resistance exercise training (RET), and the quantity of protein supplementation may be important factors for the im-provement of muscle mass and function. Although these factors should be considered comprehensively for effective improvement of muscular function in protein supplementation, relatively few studies have focused on this area. Therefore, this study was designed to investigate whether a protein blend supplement before and after resistance exercise for 12 weeks would be effective in increasing muscular function. Methods: In total, 18 participants were randomly assigned to a placebo (PLA) or protein blend supplement (PRO) group. All subjects followed the same training routine 3 times per week for 12 weeks, taking placebo or protein supplements immediately before and after each exercise session. The protein supplement consisted of 40 g of blend protein, including hydrolyzed whey protein. The RET consisted of lower body (barbell squat, dead lift, seated leg extension, and lying leg curl) and upper body (bench press, barbell rowing, preacher bench biceps curl, and dumbbell shoulder press) exercises. A repetition was defined as three sets of 10-12 times with 80% of one repetition maximum (1RM). Results: Although the PRO group had a lower protein intake in terms of total food intake than the PLA group, the mean changes in muscle circumference, strength, and exercise volume increased, especially at week 12, compared to the PLA group. Conclusion: These results suggest that the composition and timing of protein intake are more important than the total amount.
... Waldrom M et al 27 showed in a project of matched pairs in double blinding, 16 participants who were randomly assigned to a group BCAA (n = 8) or placebo (n = 8). The BCAAs were administered in a dose of 0.087 g/kg of body weight, with a ratio 2: 1: 1 of leucine, isoleucine and valine. ...
... On each occasion, participants were given detailed written and verbal instructions on completing the food logs. Dietary intake data were analyzed using the open-sourced software myfitnesspal (MyFitnessPal, Inc., San Francisco, CA, USA), which has been employed to analyze food intake data in other studies [42][43][44][45][46][47][48]. ...
Article
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We sought to determine the effects of L-leucine (LEU) or different protein supplements standardized to LEU (~3.0 g/serving) on changes in body composition, strength, and histological attributes in skeletal muscle and adipose tissue. Seventy-five untrained, college-aged males (mean ± standard error of the mean (SE); age = 21 ± 1 years, body mass = 79.2 ± 0.3 kg) were randomly assigned to an isocaloric, lipid-, and organoleptically-matched maltodextrin placebo (PLA, n = 15), LEU (n = 14), whey protein concentrate (WPC, n = 17), whey protein hydrolysate (WPH, n = 14), or soy protein concentrate (SPC, n = 15) group. Participants performed whole-body resistance training three days per week for 12 weeks while consuming supplements twice daily. Skeletal muscle and subcutaneous (SQ) fat biopsies were obtained at baseline (T1) and ~72 h following the last day of training (T39). Tissue samples were analyzed for changes in type I and II fiber cross sectional area (CSA), non-fiber specific satellite cell count, and SQ adipocyte CSA. On average, all supplement groups including PLA exhibited similar training volumes and experienced statistically similar increases in total body skeletal muscle mass determined by dual X-ray absorptiometry (+2.2 kg; time p = 0.024) and type I and II fiber CSA increases (+394 μm2 and +927 μm2; time p < 0.001 and 0.024, respectively). Notably, all groups reported increasing Calorie intakes ~600–800 kcal/day from T1 to T39 (time p < 0.001), and all groups consumed at least 1.1 g/kg/day of protein at T1 and 1.3 g/kg/day at T39. There was a training, but no supplementation, effect regarding the reduction in SQ adipocyte CSA (−210 μm2; time p = 0.001). Interestingly, satellite cell counts within the WPC (p < 0.05) and WPH (p < 0.05) groups were greater at T39 relative to T1. In summary, LEU or protein supplementation (standardized to LEU content) does not provide added benefit in increasing whole-body skeletal muscle mass or strength above PLA following 3 months of training in previously untrained college-aged males that increase Calorie intakes with resistance training and consume above the recommended daily intake of protein throughout training. However, whey protein supplementation increases skeletal muscle satellite cell number in this population, and this phenomena may promote more favorable training adaptations over more prolonged periods.
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This research is an examination of the relationships between load, performance, and salivary immunological and hormonal measures in elite-level professional Association Football (football) players. An introduction (Chapter 1), critical review of the literature (Chapter 2) and five sequential, peer-reviewed scientific investigations (Chapters 3 – 7) are presented as they were accepted in the respective scientific journals.
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PurposeThis review provides an overview of the current knowledge of the nutritional strategies to treat the signs and symptoms related to EIMD. These strategies have been organized into the following sections based upon the quality and quantity of the scientific support available: (1) interventions with a good level of evidence; (2) interventions with some evidence and require more research; and (3) potential nutritional interventions with little to-no-evidence to support efficacy.Method Pubmed, EMBASE, Scopus and Web of Science were used. The search terms ‘EIMD’ and ‘exercise-induced muscle damage’ were individually concatenated with ‘supplementation’, ‘athletes’, ‘recovery’, ‘adaptation’, ‘nutritional strategies’, hormesis’.ResultSupplementation with tart cherries, beetroot, pomegranate, creatine monohydrate and vitamin D appear to provide a prophylactic effect in reducing EIMD. β-hydroxy β-methylbutyrate, and the ingestion of protein, BCAA and milk could represent promising strategies to manage EIMD. Other nutritional interventions were identified but offered limited effect in the treatment of EIMD; however, inconsistencies in the dose and frequency of interventions might account for the lack of consensus regarding their efficacy.Conclusion There are clearly varying levels of evidence and practitioners should be mindful to refer to this evidence-base when prescribing to clients and athletes. One concern is the potential for these interventions to interfere with the exercise-recovery-adaptation continuum. Whilst there is no evidence that these interventions will blunt adaptation, it seems pragmatic to use a periodised approach to administering these strategies until data are in place to provide and evidence base on any interference effect on adaptation.
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Abstract. Delayed onset muscle soreness (DOMS) is a symptom of exercise-induced muscle damage that occurs following exercise. Previous research has indicated that branched-chain amino acid (BCAA) supplementation may attenuate exercise-induced muscle damage that causes delayed onset muscle soreness, however the results are inconsistent. The primary aim of this study was to examine the previous literature assessing the effect of BCAA supplementation on DOMS following an acute bout of exercise in adults. This review was conducted in accordance with PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-analyses), and identified peer-reviewed articles comparing a BCAA supplement to a placebo non-BCAA supplement following an acute bout of exercise. An electronic search of three databases (EbscoHost, Web of Science, and SPORTDiscus) yielded 42 articles after duplicates were removed. All studies included in the current analyis were: 1) peer-reviewed publications; 2) available in English; 3) utilized a random control design that compared a BCAA group to a placebo control group following exercise; 4) and assessed soreness of muscle tissue during recovery. DOMS was assessed in 61 participants following ingestion of a BCAA supplement over the course of these interventions. The cumulative results of 37 effects gathered from 8 studies published between 2007 and 2017 indicated that BCAA supplementation reduced DOMS following exercise training (ES = 0.7286, 95% CI: 0.5017 to 0.9555, p < 0.001). A large decrease in DOMS occurs following BCAA supplementation after exercise compared to a placebo supplement.
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Background Gestational diabetes mellitus (GDM) is increasing partly due to the obesity epidemic. Adipocytokines have thus been suggested as first trimester screening markers for GDM. In this study we explore the associations between body mass index (BMI) and serum concentrations of adiponectin, leptin, and the adiponectin/leptin ratio. Furthermore, we investigate whether these markers can improve the ability to screen for GDM in the first trimester. Methods A cohort study in which serum adiponectin and leptin were measured between gestational weeks 6+0 and 14+0 in 2590 pregnant women, categorized into normal weight, moderately obese, or severely obese. Results Lower concentrations of adiponectin were associated with GDM in all BMI groups; the association was more pronounced in BMI<35 kg/m Conclusions Low adiponectin measured in the first trimester is associated with the development of GDM; higher BMI was associated with lower performance of adiponectin, though this was insignificant. Leptin had an inverse relationship with GDM in severely obese women and did not improve the ability to predict GDM.
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Eccentric exercise results in prolonged muscle damage that may lead to muscle dysfunction. Although inflammation is essential to recover from muscle damage, excessive inflammation may also induce secondary damage, and should thus be suppressed. In this study, we investigated the effect of leucine-enriched essential amino acids on muscle inflammation and recovery after eccentric contraction. These amino acids are known to stimulate muscle protein synthesis via mammalian target of rapamycin (mTOR), which, is also considered to alleviate inflammation. Five sets of 10 eccentric contractions were induced by electrical stimulation in the tibialis anterior muscle of male SpragueDawley rats (8-9 weeks old) under anesthesia. Animals received a 1 g/kg dose of a mixture containing 40 % leucine and 60 % other essential amino acids or distilled water once a day throughout the experiment. Muscle dysfunction was assessed based on isometric dorsiflexion torque, while inflammation was evaluated by histochemistry. Gene expression of inflammatory cytokines and myogenic regulatory factors was also measured. We found that leucine-enriched essential amino acids restored full muscle function within 14 days, at which point rats treated with distilled water had not fully recovered. Indeed, muscle function was stronger 3 days after eccentric contraction in rats treated with amino acids than in those treated with distilled water. The amino acid mix also alleviated expression of interleukin-6 and impeded infiltration of inflammatory cells into muscle, but did not suppress expression of myogenic regulatory factors. These results suggest that leucine-enriched amino acids accelerate recovery from muscle damage by preventing excessive inflammation.
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This study investigated the effect of leucine supplementation on the skeletal muscle regenerative process, focusing on the remodeling of connective tissue of the fast twitch muscle tibialis anterior (TA). Young male Wistar rats were supplemented with leucine (1.35 g/kg per day); then, TA muscles from the left hind limb were cryolesioned and examined after 10 days. Although leucine supplementation induced increased protein synthesis, it was not sufficient to promote an increase in the cross-sectional area (CSA) of regenerating myofibers (p > 0.05) from TA muscles. However, leucine supplementation reduced the amount of collagen and the activation of phosphorylated transforming growth factor-β receptor type I (TβR-I) and Smad2/3 in regenerating muscles (p < 0.05). Leucine also reduced neonatal myosin heavy chain (MyHC-n) (p < 0.05), increased adult MyHC-II expression (p < 0.05) and prevented the decrease in maximum tetanic strength in regenerating TA muscles (p < 0.05). Our results suggest that leucine supplementation accelerates connective tissue repair and consequent function of regenerating TA through the attenuation of TβR-I and Smad2/3 activation. Therefore, future studies are warranted to investigate leucine supplementation as a nutritional strategy to prevent or attenuate muscle fibrosis in patients with several muscle diseases.
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Background: Protein supplements are frequently consumed by athletes and recreationally active adults to achieve greater gains in muscle mass and strength and improve physical performance. Objective: This review provides a systematic and comprehensive analysis of the literature that tested the hypothesis that protein supplements accelerate gains in muscle mass and strength resulting in improvements in aerobic and anaerobic power. Evidence statements were created based on an accepted strength of recommendation taxonomy. Data sources: English language articles were searched through PubMed and Google Scholar using protein and supplements together with performance, exercise, strength, and muscle, alone or in combination as keywords. Additional articles were retrieved from reference lists found in these papers. Study selection: Studies recruiting healthy adults between 18 and 50 years of age that evaluated the effects of protein supplements alone or in combination with carbohydrate on a performance metric (e.g., one repetition maximum or isometric or isokinetic muscle strength), metrics of body composition, or measures of aerobic or anaerobic power were included in this review. The literature search identified 32 articles which incorporated test metrics that dealt exclusively with changes in muscle mass and strength, 5 articles that implemented combined resistance and aerobic training or followed participants during their normal sport training programs, and 1 article that evaluated changes in muscle oxidative enzymes and maximal aerobic power. Study appraisal and synthesis methods: All papers were read in detail, and examined for experimental design confounders such as dietary monitoring, history of physical training (i.e., trained and untrained), and the number of participants studied. Studies were also evaluated based on the intensity, frequency, and duration of training, the type and timing of protein supplementation, and the sensitivity of the test metrics. Results: For untrained individuals, consuming supplemental protein likely has no impact on lean mass and muscle strength during the initial weeks of resistance training. However, as the duration, frequency, and volume of resistance training increase, protein supplementation may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals. Evidence also suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power. Limitations: To demonstrate measureable gains in strength and performance with exercise training and protein supplementation, many of the studies reviewed recruited untrained participants. Since skeletal muscle responses to exercise and protein supplementation differ between trained and untrained individuals, findings are not easily generalized for all consumers who may be considering the use of protein supplements. Conclusions: This review suggests that protein supplementation may enhance muscle mass and performance when the training stimulus is adequate (e.g., frequency, volume, duration), and dietary intake is consistent with recommendations for physically active individuals.
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Leucine is a key amino acid involved in the regulation of skeletal muscle protein synthesis. We assessed the effect of the supplementation of a lower-protein mixed macronutrient beverage with varying doses of leucine or a mixture of branched chain amino acids (BCAAs) on myofibrillar protein synthesis (MPS) at rest and after exercise. In a parallel group design, 40 men (21 ± 1 y) completed unilateral knee-extensor resistance exercise before the ingestion of 25 g whey protein (W25) (3.0 g leucine), 6.25 g whey protein (W6) (0.75g leucine), 6.25 g whey protein supplemented with leucine to 3.0 g total leucine (W6+Low-Leu), 6.25 g whey protein supplemented with leucine to 5.0 g total leucine (W6+High-Leu), or 6.25 g whey protein supplemented with leucine, isoleucine, and valine to 5.0 g total leucine. A primed continuous infusion of l-[ring-(13)C6] phenylalanine with serial muscle biopsies was used to measure MPS under baseline fasted and postprandial conditions in both a rested (response to feeding) and exercised (response to combined feeding and resistance exercise) leg. The area under the blood leucine curve was greatest for the W6+High-Leu group compared with the W6 and W6+Low-Leu groups (P < 0.001). In the postprandial period, rates of MPS were increased above baseline over 0-1.5 h in all treatments. Over 1.5-4.5 h, MPS remained increased above baseline after all treatments but was greatest after W25 (∼267%) and W6+High-Leu (∼220%) treatments (P = 0.002). A low-protein (6.25 g) mixed macronutrient beverage can be as effective as a high-protein dose (25 g) at stimulating increased MPS rates when supplemented with a high (5.0 g total leucine) amount of leucine. These results have important implications for formulations of protein beverages designed to enhance muscle anabolism. This trial was registered at clinicaltrials.gov as NCT 1530646.
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Delayed onset muscle soreness (DOMS) is a familiar experience for the elite or novice athlete. Symptoms can range from muscle tenderness to severe debilitating pain. The mechanisms, treatment strategies, and impact on athletic performance remain uncertain, despite the high incidence of DOMS. DOMS is most prevalent at the beginning of the sporting season when athletes are returning to training following a period of reduced activity. DOMS is also common when athletes are first introduced to certain types of activities regardless of the time of year. Eccentric activities induce micro-injury at a greater frequency and severity than other types of muscle actions. The intensity and duration of exercise are also important factors in DOMS onset. Up to six hypothesised theories have been proposed for the mechanism of DOMS, namely: lactic acid, muscle spasm, connective tissue damage, muscle damage, inflammation and the enzyme efflux theories. However, an integration of two or more theories is likely to explain muscle soreness. DOMS can affect athletic performance by causing a reduction in joint range of motion, shock attenuation and peak torque. Alterations in muscle sequencing and recruitment patterns may also occur, causing unaccustomed stress to be placed on muscle ligaments and tendons. These compensatory mechanisms may increase the risk of further injury if a premature return to sport is attempted. A number of treatment strategies have been introduced to help alleviate the severity of DOMS and to restore the maximal function of the muscles as rapidly as possible. Nonsteroidal anti-inflammatory drugs have demonstrated dosage-dependent effects that may also be influenced by the time of administration. Similarly, massage has shown varying results that may be attributed to the time of massage application and the type of massage technique used. Cryotherapy, stretching, homeopathy, ultrasound and electrical current modalities have demonstrated no effect on the alleviation of muscle soreness or other DOMS symptoms. Exercise is the most effective means of alleviating pain during DOMS, however the analgesic effect is also temporary. Athletes who must train on a daily basis should be encouraged to reduce the intensity and duration of exercise for 1–2 days following intense DOMS-inducing exercise. Alternatively, exercises targeting less affected body parts should be encouraged in order to allow the most affected muscle groups to recover. Eccentric exercises or novel activities should be introduced progressively over a period of 1 or 2 weeks at the beginning of, or during, the sporting season in order to reduce the level of physical impairment and/or training disruption. There are still many unanswered questions relating to DOMS, and many potential areas for future research.
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In the formerly published part I of this two-part review, we examined fatigue after soccer matchplay and recovery kinetics of physical performance, and cognitive, subjective and biological markers. To reduce the magnitude of fatigue and to accelerate the time to fully recover after completion, several recovery strategies are now used in professional soccer teams. During congested fixture schedules, recovery strategies are highly required to alleviate post-match fatigue, and then to regain performance faster and reduce the risk of injury. Fatigue following competition is multifactorial and mainly related to dehydration, glycogen depletion, muscle damage and mental fatigue. Recovery strategies should consequently be targeted against the major causes of fatigue. Strategies reviewed in part II of this article were nutritional intake, cold water immersion, sleeping, active recovery, stretching, compression garments, massage and electrical stimulation. Some strategies such as hydration, diet and sleep are effective in their ability to counteract the fatigue mechanisms. Providing milk drinks to players at the end of competition and a meal containing high-glycaemic index carbohydrate and protein within the hour following the match are effective in replenishing substrate stores and optimizing muscle-damage repair. Sleep is an essential part of recovery management. Sleep disturbance after a match is common and can negatively impact on the recovery process. Cold water immersion is effective during acute periods of match congestion in order to regain performance levels faster and repress the acute inflammatory process. Scientific evidence for other strategies reviewed in their ability to accelerate the return to the initial level of performance is still lacking. These include active recovery, stretching, compression garments, massage and electrical stimulation. While this does not mean that these strategies do not aid the recovery process, the protocols implemented up until now do not significantly accelerate the return to initial levels of performance in comparison with a control condition. In conclusion, scientific evidence to support the use of strategies commonly used during recovery is lacking. Additional research is required in this area in order to help practitioners establish an efficient recovery protocol immediately after matchplay, but also for the following days. Future studies could focus on the chronic effects of recovery strategies, on combinations of recovery protocols and on the effects of recovery strategies inducing an anti-inflammatory or a pro-inflammatory response.
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Background It is well documented that exercise-induced muscle damage (EIMD) decreases muscle function and causes soreness and discomfort. Branched-chain amino acid (BCAA) supplementation has been shown to increase protein synthesis and decrease muscle protein breakdown, however, the effects of BCAAs on recovery from damaging resistance training are unclear. Therefore, the aim of this study was to examine the effects of a BCAA supplementation on markers of muscle damage elicited via a sport specific bout of damaging exercise in trained volunteers. Methods Twelve males (mean ± SD age, 23 ± 2 y; stature, 178.3 ± 3.6 cm and body mass, 79.6 ± 8.4 kg) were randomly assigned to a supplement (n = 6) or placebo (n = 6) group. The damaging exercise consisted of 100 consecutive drop-jumps. Creatine kinase (CK), maximal voluntary contraction (MVC), muscle soreness (DOMS), vertical jump (VJ), thigh circumference (TC) and calf circumference (CC) were measured as markers of muscle damage. All variables were measured immediately before the damaging exercise and at 24, 48, 72 and 96 h post-exercise. Results A significant time effect was seen for all variables. There were significant group effects showing a reduction in CK efflux and muscle soreness in the BCAA group compared to the placebo (P<0.05). Furthermore, the recovery of MVC was greater in the BCAA group (P<0.05). The VJ, TC and CC were not different between groups. Conclusion The present study has shown that BCAA administered before and following damaging resistance exercise reduces indices of muscle damage and accelerates recovery in resistance-trained males. It seems likely that BCAA provided greater bioavailablity of substrate to improve protein synthesis and thereby the extent of secondary muscle damage associated with strenuous resistance exercise. Clinical Trial Registration Number: NCT01529281.
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Skeletal muscle protein turnover is modulated by intracellular signaling pathways involved in protein synthesis, degradation, and inflammation. The proinflammatory status of muscle cells, observed in pathological conditions such as cancer, aging, and sepsis, can directly modulate protein translation initiation and muscle proteolysis, contributing to negative protein turnover. In this context, branched-chain amino acids (BCAAs), especially leucine, have been described as a strong nutritional stimulus able to enhance protein translation initiation and attenuate proteolysis. Furthermore, under inflammatory conditions, BCAA can be transaminated to glutamate in order to increase glutamine synthesis, which is a substrate highly consumed by inflammatory cells such as macrophages. The present paper describes the role of inflammation on muscle remodeling and the possible metabolic and cellular effects of BCAA supplementation in the modulation of inflammatory status of skeletal muscle and the consequences on protein synthesis and degradation.
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We have reported that the acute postexercise increases in muscle protein synthesis rates, with differing nutritional support, are predictive of longer-term training-induced muscle hypertrophy. Here, we aimed to test whether the same was true with acute exercise-mediated changes in muscle protein synthesis. Eighteen men (21 ± 1 yr, 22.6 ± 2.1 kg/m(2); means ± SE) had their legs randomly assigned to two of three training conditions that differed in contraction intensity [% of maximal strength (1 repetition maximum)] or contraction volume (1 or 3 sets of repetitions): 30%-3, 80%-1, and 80%-3. Subjects trained each leg with their assigned regime for a period of 10 wk, 3 times/wk. We made pre- and posttraining measures of strength, muscle volume by magnetic resonance (MR) scans, as well as pre- and posttraining biopsies of the vastus lateralis, and a single postexercise (1 h) biopsy following the first bout of exercise, to measure signaling proteins. Training-induced increases in MR-measured muscle volume were significant (P < 0.01), with no difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3= 7.2 ± 1.9%, P = 0.18. Isotonic maximal strength gains were not different between 80%-1 and 80%-3, but were greater than 30%-3 (P = 0.04), whereas training-induced isometric strength gains were significant but not different between conditions (P = 0.92). Biopsies taken 1 h following the initial resistance exercise bout showed increased phosphorylation (P < 0.05) of p70S6K only in the 80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.
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Exercise-induced muscle damage (EIMD) occurs primarily from the performance of unaccustomed exercise, and its severity is modulated by the type, intensity, and duration of training. Although concentric and isometric actions contribute to EIMD, the greatest damage to muscle tissue is seen with eccentric exercise, where muscles are forcibly lengthened. Damage can be specific to just a few macromolecules of tissue or result in large tears in the sarcolemma, basal lamina, and supportive connective tissue, and inducing injury to contractile elements and the cytoskeleton. Although EIMD can have detrimental short-term effects on markers of performance and pain, it has been hypothesized that the associated skeletal muscle inflammation and increased protein turnover are necessary for long-term hypertrophic adaptations. A theoretical basis for this belief has been proposed, whereby the structural changes associated with EIMD influence gene expression, resulting in a strengthening of the tissue and thus protection of the muscle against further injury. Other researchers, however, have questioned this hypothesis, noting that hypertrophy can occur in the relative absence of muscle damage. Therefore, the purpose of this article will be twofold: (a) to extensively review the literature and attempt to determine what, if any, role EIMD plays in promoting skeletal muscle hypertrophy and (b) to make applicable recommendations for resistance training program design.
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Branched-chain amino acids (BCAA) supplementation has been considered an interesting nutritional strategy to improve skeletal muscle protein turnover in several conditions. In this context, there is evidence that resistance exercise (RE)-derived biochemical markers of muscle soreness (creatine kinase (CK), aldolase, myoglobin), soreness, and functional strength may be modulated by BCAA supplementation in order to favor of muscle adaptation. However, few studies have investigated such effects in well-controlled conditions in humans. Therefore, the aim of this short report is to describe the potential therapeutic effects of BCAA supplementation on RE-based muscle damage in humans. The main point is that BCAA supplementation may decrease some biochemical markers related with muscle soreness but this does not necessarily reflect on muscle functionality.
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Exercise-induced muscle damage (EIMD) leads to the degradation of protein structures within the muscle. This may subsequently lead to decrements in muscle performance and increases in intramuscular enzymes and delayed-onset muscle soreness (DOMS). Milk, which provides protein and carbohydrate (CHO), may lead to the attenuation of protein degradation and (or) an increase in protein synthesis that would limit the consequential effects of EIMD. This study examined the effects of acute milk and milk-based protein-CHO (CHO-P) supplementation on attenuating EIMD. Four independent groups of 6 healthy males consumed water (CON), CHO sports drink, milk-based CHO-P or milk (M), post EIMD. DOMS, isokinetic muscle performance, creatine kinase (CK), and myoglobin (Mb) were assessed immediately before and 24 and 48 h after EIMD. DOMS was not significantly different (p > 0.05) between groups at any time point. Peak torque (dominant) was significantly higher (p < 0.05) 48 h after CHO-P compared with CHO and CON, and M compared with CHO. Total work of the set (dominant) was significantly higher (p < 0.05) 48 h after CHO-P and M compared with CHO and CON. CK was significantly lower (p < 0.05) 48 h after CHO-P and M compared with CHO. Mb was significantly lower (p < 0.05) 48 h after CHO-P compared with CHO. At 48 h post-EIMD, milk and milk-based protein-CHO supplementation resulted in the attenuation of decreases in isokinetic muscle performance and increases in CK and Mb.
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The purpose of present review is to describe the effect of leucine supplementation on skeletal muscle proteolysis suppression in both in vivo and in vitro studies. Most studies, using in vitro methodology, incubated skeletal muscles with leucine with different doses and the results suggests that there is a dose-dependent effect. The same responses can be observed in in vivo studies. Importantly, the leucine effects on skeletal muscle protein synthesis are not always connected to the inhibition of skeletal muscle proteolysis. As a matter of fact, high doses of leucine incubation can promote suppression of muscle proteolysis without additional effects on protein synthesis, and low leucine doses improve skeletal muscle protein ynthesis but have no effect on skeletal muscle proteolysis. These research findings may have an important clinical relevancy, because muscle loss in atrophic states would be reversed by specific leucine supplementation doses. Additionally, it has been clearly demonstrated that leucine administration suppresses skeletal muscle proteolysis in various catabolic states. Thus, if protein metabolism changes during different atrophic conditions, it is not surprising that the leucine dose-effect relationship must also change, according to atrophy or pathological state and catabolism magnitude. In conclusion, leucine has a potential role on attenuate skeletal muscle proteolysis. Future studies will help to sharpen the leucine efficacy on skeletal muscle protein degradation during several atrophic states.
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The purpose of this study was to determine the effect of leucine supplementation on indices of muscle damage following eccentric-based resistance exercise. In vitro, the amino acid leucine has been shown to reduce proteolysis and stimulate protein synthesis. Twenty-seven untrained males (height 178.6±5.5 cm; body mass 77.7±13.5 kg; age 21.3±1.6 years) were randomly divided into three groups; leucine (L) (n=10), placebo (P) (n=9) and control (C) (n=8). The two experimental groups (L and P) performed 100 depth jumps from 60 cm and six sets of ten repetitions of eccentric-only leg presses. Either leucine (250 mg/kg bm) or placebo was ingested 30 min before, during and immediately post-exercise and the morning of each recovery day following exercise. Muscle function was determined by peak force during an isometric squat and by jump height during a static jump at pre-exercise (PRE) and 24, 48, 72, and 96 h post-exercise (24, 48, 72, 96 h). Additionally, at these time points each group's serum levels of creatine kinase (CK) and myoglobin (Mb) along with perceived feelings of muscle soreness were determined. None of the C group dependent variables was altered by the recurring testing procedures. Peak force was significantly decreased across all time points for both experimental groups. The L group experienced an attenuated drop in mean peak force across all post-exercise time points compared to the P group. Jump height significantly decreased from PRE for both the L and P group at 24 h and 48 h. CK and Mb was significantly elevated from PRE for both experimental groups at 24 h. Muscle soreness increased across all time points for the both the L and P group, and the L group experienced a significantly higher increase in mean muscle soreness post-exercise. Following exercise-induced muscle damage, high-dose leucine supplementation may help maintain force output during isometric contractions, however, not force output required for complex physical tasks thereby possibly limiting its ergogenic effectiveness.
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The quest to increase lean body mass is widely pursued by those who lift weights. Research is lacking, however, as to the best approach for maximizing exercise-induced muscle growth. Bodybuilders generally train with moderate loads and fairly short rest intervals that induce high amounts of metabolic stress. Powerlifters, on the other hand, routinely train with high-intensity loads and lengthy rest periods between sets. Although both groups are known to display impressive muscularity, it is not clear which method is superior for hypertrophic gains. It has been shown that many factors mediate the hypertrophic process and that mechanical tension, muscle damage, and metabolic stress all can play a role in exercise-induced muscle growth. Therefore, the purpose of this paper is twofold: (a) to extensively review the literature as to the mechanisms of muscle hypertrophy and their application to exercise training and (b) to draw conclusions from the research as to the optimal protocol for maximizing muscle growth.
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Muscle tissue may be damaged following intense prolonged training as a consequence of both metabolic and mechanical factors. Serum levels of skeletal muscle enzymes or proteins are markers of the functional status of muscle tissue, and vary widely in both pathological and physiological conditions. Creatine kinase, lactate dehydrogenase, aldolase, myoglobin, troponin, aspartate aminotransferase, and carbonic anhydrase CAIII are the most useful serum markers of muscle injury, but apoptosis in muscle tissues subsequent to strenuous exercise may be also triggered by increased oxidative stress. Therefore, total antioxidant status can be used to evaluate the level of stress in muscle by other markers, such as thiobarbituric acid-reactive substances, malondialdehyde, sulfhydril groups, reduced glutathione, oxidized glutathione, superoxide dismutase, catalase and others. As the various markers provide a composite picture of muscle status, we recommend using more than one to provide a better estimation of muscle stress.
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The purpose of this study was to investigate whether short-term amino acid supplementation could maintain a short-term net anabolic hormonal profile and decrease muscle cell damage during a period of high-intensity resistance training (overreaching), thereby enhancing recovery and decreasing the risk of injury and illness. Eight previously resistance trained males were randomly assigned to either a high branched chain amino acids (BCAA) or placebo group. Subjects consumed the supplement for 3 weeks before commencing a fourth week of supplementation with concomitant high-intensity total-body resistance training (overreaching) (3 x 6-8 repetitions maximum, 8 exercises). Blood was drawn prior to and after supplementation, then again after 2 and 4 days of training. Serum was analyzed for testosterone, cortisol, and creatine kinase. Serum testosterone levels were significantly higher (p < 0.001), and cortisol and creatine kinase levels were significantly lower (p < 0.001, and p = 0.004, respectively) in the BCAA group during and following resistance training. These findings suggest that short-term amino acid supplementation, which is high in BCAA, may produce a net anabolic hormonal profile while attenuating training-induced increases in muscle tissue damage. Athletes' nutrient intake, which periodically increases amino acid intake to reflect the increased need for recovery during periods of overreaching, may increase subsequent competitive performance while decreasing the risk of injury or illness.
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Normally, skeletal muscle mass is unchanged, beyond periods of growth, but it begins to decline in the fourth or fifth decade of life. The mass of skeletal muscle is maintained by ingestion of protein-containing meals. With feeding, muscle protein synthesis (MPS) is stimulated and a small suppression of muscle protein breakdown (MPB) occurs, such that protein balance becomes positive (MPS>MPB). As the postprandial period subsides and a transition toward fasting occurs, the balance of muscle protein turnover becomes negative again (MPB>MPS). Thus, during maintenance of skeletal muscle mass, the long-term net result is that MPS is balanced by MPB. Acutely, however, it is of interest to determine what regulates feeding-induced increases in MPS, since it appears that, in a number of scenarios (for example aging, disuse, and wasting diseases), a suppression of MPS in response to feeding is a common finding. In fact, recent findings point to the fact that loss of skeletal muscle mass with disuse and aging is due not chronic changes in MPS or MPB, but to a blunted feeding-induced rise in MPS. Resistance exercise is a potent stimulator of MPS and appears to synergistically enhance the gains stimulated by feeding. As such, resistance exercise is an important countermeasure to disuse atrophy and to age-related declines in skeletal muscle mass. What is less well understood is how the intensity and volume of the resistance exercise stimulus is sufficient to result in rises in MPS. Recent advances in this area are discussed here, with a focus on human in vivo data.
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A study of a sample provides only an estimate of the true (population) value of an outcome statistic. A report of the study therefore usually includes an inference about the true value. Traditionally, a researcher makes an inference by declaring the value of the statistic statistically significant or nonsignificant on the basis of a P value derived from a null-hypothesis test. This approach is confusing and can be misleading, depending on the magnitude of the statistic, error of measurement, and sample size. The authors use a more intuitive and practical approach based directly on uncertainty in the true value of the statistic. First they express the uncertainty as confidence limits, which define the likely range of the true value. They then deal with the real-world relevance of this uncertainty by taking into account values of the statistic that are substantial in some positive and negative sense, such as beneficial or harmful. If the likely range overlaps substantially positive and negative values, they infer that the outcome is unclear; otherwise, they infer that the true value has the magnitude of the observed value: substantially positive, trivial, or substantially negative. They refine this crude inference by stating qualitatively the likelihood that the true value will have the observed magnitude (eg, very likely beneficial). Quantitative or qualitative probabilities that the true value has the other 2 magnitudes or more finely graded magnitudes (such as trivial, small, moderate, and large) can also be estimated to guide a decision about the utility of the outcome.
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Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.
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Muscular overuse after high force eccentric muscle action is associated with structural damage of the contractile apparatus that can be observed as Z-line steaming and myofibrillar disruption. Mechanical stress is the major contributing factor for inducing muscle injury, which initiates a cascade of processes resulting in skeletal muscle damage. Disturbances in Ca2+ homeostasis with elevated intracellular [Ca2+] activates the nonlysomal cysteine protease, calpain. Calpain is assumed to play an important role in triggering the response of skeletal muscle protein breakdown, of inflammatory changes, and of regeneration processes in response to eccentric muscle action. The inflammatory response is attributed to changes in hormone and cytokine levels in blood and skeletal muscle. To assess the amount of skeletal muscle damage, plasma CK activity and plasma myoglobin levels have been widely used as markers for muscle injury. As the cytosolic proteins do not necessarily reflect the amount of structural damage, structurally bound proteins such as myosin heavy chains and troponin have been investigated. This paper briefly reviews the cascade of events causing muscle cell injury after unaccustomed eccentric muscle action and the potential of muscle proteins as markers of skeletal muscle damage.
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In eccentric exercise the contracting muscle is forcibly lengthened; in concentric exercise it shortens. While concentric contractions initiate movements, eccentric contractions slow or stop them. A unique feature of eccentric exercise is that untrained subjects become stiff and sore the day afterwards because of damage to muscle fibres. This review considers two possible initial events as responsible for the subsequent damage, damage to the excitation-contraction coupling system and disruption at the level of the sarcomeres. Other changes seen after eccentric exercise, a fall in active tension, shift in optimum length for active tension, and rise in passive tension, are seen, on balance, to favour sarcomere disruption as the starting point for the damage. As well as damage to muscle fibres there is evidence of disturbance of muscle sense organs and of proprioception. A second period of exercise, a week after the first, produces much less damage. This is the result of an adaptation process. One proposed mechanism for the adaptation is an increase in sarcomere number in muscle fibres. This leads to a secondary shift in the muscle's optimum length for active tension. The ability of muscle to rapidly adapt following the damage from eccentric exercise raises the possibility of clinical applications of mild eccentric exercise, such as for protecting a muscle against more major injuries.
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This study tests the hypothesis that a dose of 6 g of orally administered essential amino acids (EAAs) stimulates net muscle protein balance in healthy volunteers when consumed 1 and 2 h after resistance exercise. Subjects received a primed constant infusion of L-[(2)H(5)]phenylalanine and L-[1-(13)C]leucine. Samples from femoral artery and vein and biopsies from vastus lateralis were obtained. Arterial EAA concentrations increased severalfold after drinks. Net muscle protein balance (NB) increased proportionally more than arterial AA concentrations in response to drinks, and it returned rapidly to basal values when AA concentrations decreased. Area under the curve for net phenylalanine uptake above basal value was similar for the first hour after each drink (67 +/- 17 vs. 77 +/- 20 mg/leg, respectively). Because the NB response was double the response to two doses of a mixture of 3 g of EAA + 3 g of nonessential AA (NEAA) (14), we conclude that NEAA are not necessary for stimulation of NB and that there is a dose-dependent effect of EAA ingestion on muscle protein synthesis.
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The repeated bout effect refers to the adaptation whereby a single bout of eccentric exercise protects against muscle damage from subsequent eccentric bouts. While the mechanism for this adaptation is poorly understood there have been significant recent advances in the understanding of this phenomenon. The purpose of this review is to provide an update on previously proposed theories and address new theories that have been advanced. The potential adaptations have been categorized as neural, mechanical and cellular. There is some evidence to suggest that the repeated bout effect is associated with a shift toward greater recruitment of slow twitch motor units. However, the repeated bout effect has been demonstrated with electrically stimulated contractions, indicating that a peripheral, non-neural adaptation predominates. With respect to mechanical adaptations there is evidence that both dynamic and passive muscle stiffness increase with eccentric training but there are no studies on passive or dynamic stiffness adaptations to a single eccentric bout. The role of the cytoskeleton in regulating dynamic stiffness is a possible area for future research. With respect to cellular adaptations there is evidence of longitudinal addition of sarcomeres and adaptations in the inflammatory response following an initial bout of eccentric exercise. Addition of sarcomeres is thought to reduce sarcomere strain during eccentric contractions thereby avoiding sarcomere disruption. Inflammatory adaptations are thought to limit the proliferation of damage that typically occurs in the days following eccentric exercise. In conclusion, there have been significant advances in the understanding of the repeated bout effect, however, a unified theory explaining the mechanism or mechanisms for this protective adaptation remains elusive.
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This study examined the fatigue effects of stretch-shortening cycle exercises of different intensity and duration on stretch reflex EMG and mechanical responses of the triceps surae muscle. Twelve subjects performed either a 10-km run ( n=6) or short but exhaustive rebound exercise on a sledge apparatus ( n=6). Passive reflex tests (mechanically induced ankle dorsiflexions) were examined before, after as well as 2 h, 2 and 7 days after exercise. Mechanical reflex responses were recorded from the ergometer torque signal. An acute contractile failure was observed as large reductions in twitch responses, especially in the sledge subgroup who showed high post-exercise peak blood lactate and an increased EMG/torque ratio. Independently of the exercise, the delayed fatigue analysis revealed strong relationships between the reflex-induced EMG and mechanical changes. In addition to muscle damage, these results may be explained by inhibitory effects via the sensitisation of small muscle afferents particularly during the exercise-induced delayed recovery process.
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To measure daily energy expenditure (DEE) with indirect calorimetric facilities in sedentary and active subjects. To estimate daily energy needs with the FAO/WHO/UNU (1985) procedures (EDEE) and estimated energy requirement (EER) with the dietary reference intakes 2002 (DRI) in healthy adults with sedentary or high-activity conditions. To compare estimated daily energy needs with their measured values. Two groups of healthy subjects were tested under sedentary or high-activity conditions. In both groups, resting energy expenditure was measured after a 12-h overnight fast. DEE and basal metabolic rate (BMR) values were also measured with indirect calorimetry and compared to the relevant predicted values. Physical activity level and BMR were also estimated. A total of 45 sedentary (26 men and 19 women) and 69 active subjects (43 men and 26 women) aged 18-30 and 30-60 y. Measured daily energy expenditure (MDEE) was significantly lower than EDEE in sedentary men and women and in active men for the two age groups considered (P<0.05). EER was significantly lower than EDEE in both sedentary and active subjects of each subgroup (P<0.05). The FAO/WHO/UNU (1985) procedures may overestimate daily energy needs, particularly in sedentary individuals. However, DRI (2002) are probably more adapted to estimate real daily energy needs in sedentary and active subjects in comparison to the FAO/WHO/UNU (1985) procedures.
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Delayed onset muscle soreness (DOMS) is a familiar experience for the elite or novice athlete. Symptoms can range from muscle tenderness to severe debilitating pain. The mechanisms, treatment strategies, and impact on athletic performance remain uncertain, despite the high incidence of DOMS. DOMS is most prevalent at the beginning of the sporting season when athletes are returning to training following a period of reduced activity. DOMS is also common when athletes are first introduced to certain types of activities regardless of the time of year. Eccentric activities induce micro-injury at a greater frequency and severity than other types of muscle actions. The intensity and duration of exercise are also important factors in DOMS onset. Up to six hypothesised theories have been proposed for the mechanism of DOMS, namely: lactic acid, muscle spasm, connective tissue damage, muscle damage, inflammation and the enzyme efflux theories. However, an integration of two or more theories is likely to explain muscle soreness. DOMS can affect athletic performance by causing a reduction in joint range of motion, shock attenuation and peak torque. Alterations in muscle sequencing and recruitment patterns may also occur, causing unaccustomed stress to be placed on muscle ligaments and tendons. These compensatory mechanisms may increase the risk of further injury if a premature return to sport is attempted.A number of treatment strategies have been introduced to help alleviate the severity of DOMS and to restore the maximal function of the muscles as rapidly as possible. Nonsteroidal anti-inflammatory drugs have demonstrated dosage-dependent effects that may also be influenced by the time of administration. Similarly, massage has shown varying results that may be attributed to the time of massage application and the type of massage technique used. Cryotherapy, stretching, homeopathy, ultrasound and electrical current modalities have demonstrated no effect on the alleviation of muscle soreness or other DOMS symptoms. Exercise is the most effective means of alleviating pain during DOMS, however the analgesic effect is also temporary. Athletes who must train on a daily basis should be encouraged to reduce the intensity and duration of exercise for 1-2 days following intense DOMS-inducing exercise. Alternatively, exercises targeting less affected body parts should be encouraged in order to allow the most affected muscle groups to recover. Eccentric exercises or novel activities should be introduced progressively over a period of 1 or 2 weeks at the beginning of, or during, the sporting season in order to reduce the level of physical impairment and/or training disruption. There are still many unanswered questions relating to DOMS, and many potential areas for future research.
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Background Prostate-specific antigen (PSA) test is of paramount importance as a diagnostic tool for the detection and monitoring of patients with prostate cancer. In the presence of interfering factors such as heterophilic antibodies or anti-PSA antibodies the PSA test can yield significantly falsified results. The prevalence of these factors is unknown. Methods We determined the recovery of PSA concentrations diluting patient samples with a standard serum of known PSA concentration. Based on the frequency distribution of recoveries in a pre-study on 268 samples, samples with recoveries <80% or >120% were defined as suspect, re-tested and further characterized to identify the cause of interference. Results A total of 1158 consecutive serum samples were analyzed. Four samples (0.3%) showed reproducibly disturbed recoveries of 10%, 68%, 166% and 4441%. In three samples heterophilic antibodies were identified as the probable cause, in the fourth anti-PSA-autoantibodies. The very low recovery caused by the latter interference was confirmed in serum, as well as heparin- and EDTA plasma of blood samples obtained 6 months later. Analysis by eight different immunoassays showed recoveries ranging between <10% and 80%. In a follow-up study of 212 random plasma samples we found seven samples with autoantibodies against PSA which however did not show any disturbed PSA recovery. Conclusions About 0.3% of PSA determinations by the electrochemiluminescence assay (ECLIA) of Roche diagnostics are disturbed by heterophilic or anti-PSA autoantibodies. Although they are rare, these interferences can cause relevant misinterpretations of a PSA test result.
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Protein-leucine supplement ingestion following strenuous endurance exercise accentuates skeletal-muscle protein synthesis and adaptive molecular responses, but the underlying transcriptome is uncharacterized. In a randomized single-blind triple-crossover design, 12 trained men completed 100 min of high-intensity cycling then ingested either 70/15/180/30g protein/leucine/carbohydrate/fat (15LEU), 23/5/180/30g (5LEU) or 0/0/274/30g (CON) beverages during the first 90 min of a 240-min recovery period. Vastus lateralis muscle samples (30 and 240-min post-exercise) underwent transcriptome analysis by microarray followed by bioinformatic analysis. Gene expression was regulated by Protein-leucine in a dose-dependent manner impacting the inflammatory response, muscle growth and development. At 30 min, 15LEU and 5LEU vs. CON activated transcriptome networks with geneset functions involving cell-cycle arrest (Z-score 2.0-2.7; P<0.01), leukocyte maturation (1.7; P=0.007), cell viability (2.4; P=0.005), promyogenic networks encompassing myocyte differentiation and myogenin (MYOD1, MYOG), and a proteinaceous extracellular matrix, adhesion, and development programme correlated with plasma lysine, arginine, tyrosine, taurine, glutamic acid, and asparagine concentrations. High protein-leucine dose (15LEU-5LEU) activated an IL1β-centered proinflammatory network and leukocyte migration, differentiation, and survival functions (2.0-2.6; <0.001). By 240 min, the protein-leucine transcriptome was anti-inflammatory and promyogenic (IL-6, NF-κβ, SMAD, STAT3 network inhibition), with overrepresented functions including decreased leukocyte migration and connective tissue development (-1.8-2.4; P<0.01), increased apoptosis of myeloid and muscle cells (2.2-3.0; P<0.002) and cell metabolism (2.0-2.4; P<0.01). The analysis suggests protein-leucine ingestion modulates inflammatory-myogenic regenerative processes during skeletal muscle recovery from endurance exercise. Further cellular and translational research is warranted to validate amino acid-mediated myeloid and myocellular mechanisms within skeletal-muscle functional plasticity.
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Branched-chain amino acids promote muscle-protein synthesis, reduce protein oxidation and have positive effects on mitochondrial biogenesis and reactive oxygen species scavenging. The purpose of the study was to determine the potential benefits of branched-chain amino acids supplementation on changes in force capacities, plasma amino acids concentration and muscle metabolic alterations after exercise-induced muscle damage. (31)P magnetic resonance spectroscopy and biochemical analyses were used to follow the changes after such damage. Twenty six young healthy men were randomly assigned to supplemented branched-chain amino acids or placebo group. Knee extensors maximal voluntary isometric force was assessed before and on four days following exercise-induced muscle damage. Concentrations in phosphocreatine [PCr], inorganic phosphate [Pi] and pH were measured during a standardized rest-exercise-recovery protocol before, two (D2) and four (D4) days after exercise-induced muscle damage. No significant difference between groups was found for changes in maximal voluntary isometric force (-24% at D2 and -21% at D4). Plasma alanine concentration significantly increased immediately after exercise-induced muscle damage (+25%) in both groups while concentrations in glycine, histidine, phenylalanine and tyrosine decreased. No difference between groups was found in the increased resting [Pi] (+42% at D2 and +34% at D4), decreased resting pH (-0.04 at D2 and -0.03 at D4) and the slower PCr recovery rate (-18% at D2 and -24% at D4). The damaged muscle was not able to get benefits out of the increased plasma branched-chain amino acids availability to attenuate changes in indirect markers of muscle damage and muscle metabolic alterations following exercise-induced muscle damage. Copyright © 2015 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.
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Background: Postexercise protein or amino acid ingestion restores muscle protein synthesis in older adults and represents an important therapeutic strategy for aging muscle. However, the precise nutritional factors involved are unknown. Objective: The purpose of this study was to determine the role of increased postexercise Leu ingestion on skeletal muscle myofibrillar protein synthesis (MyoPS), mammalian/mechanistic target of rapamycin complex 1 signaling, and amino acid transporter (AAT) mRNA expression in older men over a 24-h post-resistance exercise (RE) time course. Methods: During a stable isotope infusion trial (l-[ring-(13)C6]Phe; l-[1-(13)C]Leu), older men performed RE and, at 1 h after exercise, ingested 10 g of essential amino acids (EAAs) containing either a Leu content similar to quality protein (control, 1.85 g of Leu, n = 7) or enriched Leu (LEU; 3.5 g of Leu, n = 8). Muscle biopsies (vastus lateralis) were obtained at rest and 2, 5, and 24 h after exercise. Results: p70 S6 kinase 1 phosphorylation was increased in each group at 2 h (P < 0.05), whereas 4E binding protein 1 phosphorylation increased only in the LEU group (P < 0.05). MyoPS was similarly increased (∼90%) above basal in each group at 5 h (P < 0.05) and remained elevated (∼90%) at 24 h only in the LEU group (P < 0.05). The mRNA expression of select AATs was increased at 2 and 5 h in each group (P < 0.05), but AAT expression was increased at 24 h only in the LEU group (P < 0.05). Conclusions: Leu-enriched EAA ingestion after RE may prolong the anabolic response and sensitivity of skeletal muscle to amino acids in older adults. These data emphasize the potential importance of adequate postexercise Leu ingestion to enhance the response of aging muscle to preventive or therapeutic exercise-based rehabilitation programs. This trial was registered at clinicaltrials.gov as NCT00891696.
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SUMMARY In order to stimulate further adaptation toward specific training goals, progressive resistance training (RT) protocols are necessary. The optimal characteristics of strength-specific programs include the use of concentric (CON), eccentric (ECC), and isometric muscle actions and the performance of bilateral and unilateral single- and multiple-joint exercises. In addition, it is recommended that strength programs sequence exercises to optimize the preservation of exercise intensity (large before small muscle group exercises, multiple-joint exercises before single-joint exercises, and higher-intensity before lower-intensity exercises). For novice (untrained individuals with no RT experience or who have not trained for several years) training, it is recommended that loads correspond to a repetition range of an 8-12 repetition maximum (RM). For intermediate (individuals with approximately 6 months of consistent RT experience) to advanced (individuals with years of RT experience) training, it is recommended that individuals use a wider loading range from 1 to 12 RM in a periodized fashion with eventual emphasis on heavy loading (1-6 RM) using 3- to 5-min rest periods between sets performed at a moderate contraction velocity (1-2 s CON; 1-2 s ECC). When training at a specific RM load, it is recommended that 2-10% increase in load be applied when the individual can perform the current workload for one to two repetitions over the desired number. The recommendation for training frequency is 2-3 dIwkj1 for novice training, 3-4 dIwkj1 for intermediate training, and 4-5 dIwkj1 for advanced training. Similar program designs are recom- mended for hypertrophy training with respect to exercise selection and frequency. For loading, it is recommended that loads corresponding to 1-12 RM be used in periodized fashion with emphasis on the 6-12 RM zone using 1- to 2-min rest periods between sets at a moderate velocity. Higher volume, multiple-set programs are recommended for maximizing hypertrophy. Progression in power training entails two general loading strategies: 1) strength training and 2) use of light loads (0-60% of 1 RM for lower body exercises; 30-60% of 1 RM for upper body exercises) performed at a fast contraction velocity with 3-5 min of rest between sets for multiple sets per exercise (three to five sets). It is also recommended that emphasis be placed on multiple-joint exercises especially those involving the total body. For local muscular endurance training, it is recommended that light to moderate loads (40-60% of 1 RM) be performed for high repetitions (915) using short rest periods (G90 s). In the interpretation of this position stand as with prior ones, recommendations should be applied in context and should be contingent upon an individual's target goals, physical capacity, and training
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The objective of this review is to analyze in detail the microscopic structure and relations among muscular fibers, endomysium, perimysium, epimysium and deep fasciae. In particular, the multilayer organization and the collagen fiber orientation of these elements are reported. The endomysium, perimysium, epimysium and deep fasciae have not just a role of containment, limiting the expansion of the muscle with the disposition in concentric layers of the collagen tissue, but are fundamental elements for the transmission of muscular force, each one with a specific role. From this review it appears that the muscular fibers should not be studied as isolated elements, but as a complex inseparable from their fibrous components. The force expressed by a muscle depends not only on its anatomical structure, but also the angle at which its fibers are attached to the intramuscular connective tissue and the relation with the epimysium and deep fasciae.
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The authors examined the effect of branched-chain amino acid (BCAA) supplementation on squat-exercise-induced delayed-onset muscle soreness (DOMS) using 12 young, healthy, untrained female participants. The experiment was conducted with a crossover double-blind design. In the morning on the exercise-session day, the participants ingested either BCAA (isoleucine:leucine:valine = 1:2.3:1.2) or dextrin at 100 mg/kg body weight before the squat exercise, which consisted of 7 sets of 20 squats/set with 3-min intervals between sets. DOMS showed a peak on Days 2 and 3 in both trials, but the level of soreness was significantly lower in the BCAA trial than in the placebo. Leg-muscle force during maximal voluntary isometric contractions was measured 2 d after exercise (Day 3), and the BCAA supplementation suppressed the muscle-force decrease (to ~80% of the value recorded under the control conditions) observed in the placebo trial. Plasma BCAA concentrations, which decreased after exercise in the placebo trial, were markedly elevated during the 2 hr postexercise in the BCAA trial. Serum myoglobin concentration was increased by exercise in the placebo but not in the BCAA trial. The concentration of plasma elastase as an index of neutrophil activation appeared to increase after the squat exercise in both trials, but the change in the elastase level was significant only in the placebo trial. These results suggest that muscle damage may be suppressed by BCAA supplementation.
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The purpose of this study was to examine the role of branched-chain amino acid (BCAA) supplementation during recovery from intense eccentric exercise. Twenty-four non-weight-trained males were assigned to one of two groups: one group (supplementary, SUP) ingested BCAA beverages (n = 12); the second group (placebo, PLA) ingested artificially flavored water (n = 12). Diet was controlled throughout the testing period to match habitual intake. The eccentric exercise protocol consisted of 12 x 10 repetitions of unilateral eccentric knee extension exercise at 120% concentric one repetition maximum. On the day of the exercise, supplements were consumed 30 min before exercise, 1.5 h after exercise, between lunch and dinner, and before bed. On the following 2 d, four supplements were consumed between meals. Muscle soreness, muscle function, and putative blood markers of muscle damage were assessed before and after (1, 8, 24, 48, and 72 h) exercise. Muscle function decreased after the eccentric exercise (P < 0.0001), but the degree of force loss was unaffected by BCAA ingestion (51% +/- 3% with SUP vs -48% +/- 7% with PLA). A decrease in flexed muscle soreness was observed in SUP compared with PLA at 48 h (21 +/- 3 mm vs 32 +/- 3 mm, P = 0.02) and 72 h (17 +/- 3 mm vs 27 +/- 4 mm, P = 0.038). Flexed muscle soreness, expressed as area under the curve, was lower in SUP than in PLA (P = 0.024). BCAA supplementation may attenuate muscle soreness, but it does not ameliorate eccentric exercise-induced decrements in muscle function or increases in reputed blood markers of muscle damage, when consumed before exercise and for 3 d after an eccentric exercise bout.
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The present study was conducted to examine alterations in plasma free amino acid concentrations induced by squat exercise and branched-chain amino acid (BCAA) supplementation in young, untrained female subjects. In the morning on the exercise session day, participants ingested drinks containing either BCAA (isoleucine:leucine:valine=1:2.3:1.2) or dextrin (placebo) at 0.1 g/kg body weight 15 min before a squat exercise session, which consisted of 7 sets of 20 squats, with 3 min intervals between sets. In the placebo trial, plasma BCAA concentrations were decreased subsequent to exercise, whereas they were significantly increased in the BCAA trial until 2 h after exercise. Marked changes in other free amino acids in response to squat exercise and BCAA supplementation were observed. In particular, plasma concentrations of methionine and aromatic amino acids were temporarily decreased in the BCAA trial, being significantly lower than those in the placebo trial. These results suggest that BCAA intake before exercise affects methionine and aromatic amino acid metabolism.
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Statistical guidelines and expert statements are now available to assist in the analysis and reporting of studies in some biomedical disciplines. We present here a more progressive resource for sample-based studies, meta-analyses, and case studies in sports medicine and exercise science. We offer forthright advice on the following controversial or novel issues: using precision of estimation for inferences about population effects in preference to null-hypothesis testing, which is inadequate for assessing clinical or practical importance; justifying sample size via acceptable precision or confidence for clinical decisions rather than via adequate power for statistical significance; showing SD rather than SEM, to better communicate the magnitude of differences in means and nonuniformity of error; avoiding purely nonparametric analyses, which cannot provide inferences about magnitude and are unnecessary; using regression statistics in validity studies, in preference to the impractical and biased limits of agreement; making greater use of qualitative methods to enrich sample-based quantitative projects; and seeking ethics approval for public access to the depersonalized raw data of a study, to address the need for more scrutiny of research and better meta-analyses. Advice on less contentious issues includes the following: using covariates in linear models to adjust for confounders, to account for individual differences, and to identify potential mechanisms of an effect; using log transformation to deal with nonuniformity of effects and error; identifying and deleting outliers; presenting descriptive, effect, and inferential statistics in appropriate formats; and contending with bias arising from problems with sampling, assignment, blinding, measurement error, and researchers' prejudices. This article should advance the field by stimulating debate, promoting innovative approaches, and serving as a useful checklist for authors, reviewers, and editors.
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A prior bout of exercise is well known to confer protection from subsequent eccentric bouts (i.e. repeated bout effect; RBE), which may be fostered through neural adaptations, specifically a shift in the frequency content of the surface electromyogram (EMG). It is currently not clear whether chronically resistance trained men are capable of a RBE driven by neural adaptations. Eleven resistance trained men (23.5+/-3.4 yrs) performed 100 eccentric actions of the barbell bench press exercise, followed by an equivalent bout 14 days later. Indirect markers of muscle damage (i.e. force production, soreness) along with surface EMG were measured before and through 48 h of recovery. Median frequency and maximal isometric force demonstrated time main effects (p>0.05), but no RBE. A prior bout of eccentric exercise does not confer a RBE for indirect markers of muscle injury or elicit changes in the frequency content of the EMG signal in resistance trained men.
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Skeletal muscle can undergo rapid growth in response to a sudden increase in work load. For example, the rat soleus muscle increases in weight by 40% within six days after the tendon of the synergistic gastrocnemius is sectioned. Such growth of the overworked muscle involves an enlargement of muscle fibers and occasional longitudinal splitting. Hypertrophy leads to greater maximal tension development, although decreased contraction time and reduced contractility have also been reported. Unlike normal developmental growth, work-induced hypertrophy can be induced in hypophysectomized or diabetic animals. This process thus appears independent of growth hormone and insulin as well as testosterone and thyroid hormones. Hypertrophy of the soleus can also be induced in fasting animals, in which there is a generalized muscle wasting. Thus muscular activity takes precedence over endocrine influences on muscle size. The increase in muscle weight reflects an increase in protein, especially sarcoplasmic protein, and results from greater protein synthesis and reduced protein breakdown. Within several hours after operation, the hypertrophying soleus shows more rapid uptake of certain amino acids and synthesis of phosphatidyl-inositol. By 8 hours, protein synthesis is enhanced. RNA synthesis also increases, and hypertrophy can be prevented with actinomycin D. Nuclear DNA synthesis also increases on the second day after operation and leads to a greater DNA content. The significance of the increased RNA and DNA synthesis is not clear, since most of it occurs in interstitial and satellite cells. The proliferation of the non-muscle cells seems linked to the growth of the muscle fibers; in addition, factors causing muscle atrophy (e.g. denervation) decrease DNA synthesis by such cells. In order to define more precisely the early events in hypertrophy, the effects of contractile activity were studied in rat muscles in vitro. Electrical stimulation enhanced active transport of certain amino acids within an hour, and the magnitude of this effect depended on the amount of contractile activity. Stimulation or passive stretch of the soleus or diaphragm also retarded protein degradation. Presumably these effects of mechanical activity contribute to the changes occuring during hypertrophy in vivo. However, under the same conditions, or even after more prolonged stimulation, no change in rates of protein synthesis was detected. These findings with passive tension in vitro are particularly interesting, since passive stretch has been reported to retard atrophy or to induce hypertrophy of denervated muscle in vivo. It is suggested that increased tension development (either passive or active) is the critical event in initiating compensatory growth.
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1. The present study examined if the presence of creatine kinase (CK) inhibitors might explain the large variability in blood levels of CK among subjects after exercise-induced muscle damage. 2. Twenty-four women performed an eccentric exercise with the forearm flexors and were then classified as no CK responders, low CK responders and high CK responders. High CK responders repeated the exercise two weeks later (bout two). 3. Sera from high CK responders were mixed with sera from no CK responders or low CK responders. Also, serum from high CK responders obtained after bout one was mixed with the same subject's serum from after bout two. 4. In all cases, the differences between the expected and observed CK activity for the mixes were within the expected variability for the assay. 5. Although CK inhibitors have been previously observed in sera from patients with muscle injury or disease, we were unable to demonstrate the presence of CK inhibitors in the sera from subjects who showed evidence of exercise-induced muscle damage.
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To examine the changes of plasma beta-endorphin (beta-EP) concentrations in response to various heavy-resistance exercise protocols, eight healthy male subjects randomly performed each of six heavy-resistance exercise protocols, which consisted of identically ordered exercises carefully designed to control for the repetition maximum (RM) resistance (5 vs. 10 RM), rest period length (1 vs. 3 min), and total work (joules). Plasma beta-EP, ammonia, whole blood lactate and serum cortisol, creatine kinase, urea, and creatinine were determined preexercise, midexercise, immediately postexercise, and at various time points after the exercise session (5 min-48 h), depending on the specific blood variable examined. Only the high total work-exercise protocol [1 min rest, 10 RM load (H10/1)] demonstrated significant increases in plasma beta-EP and serum cortisol at midexercise and 0, 5, and 15 min postexercise. Increases in lactate were observed after all protocols, but the largest increases were observed after the H10/1 protocol. Within the H10/1 protocol, lactate concentrations were correlated (r = 0.82, P < 0.05) with plasma beta-EP concentrations. Cortisol increases were significantly correlated (r = 0.84) with 24-h peak creatine kinase values. The primary finding of this investigation was that beta-EP responds differently to various heavy-resistance exercise protocols. In heavy-resistance exercise, it appears that the duration of the force production and the length of the rest periods between sets are key exercise variables that influence increases in plasma beta-EP and serum cortisol concentrations. Furthermore the H10/1 protocol's significant challenge to the acid-base status of the blood, due to marked increases in whole blood lactate, may be associated with mechanisms modulating peripheral blood concentrations of beta-EP and cortisol.
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Stretch-shortening cycle (SSC) in human skeletal muscle gives unique possibilities to study normal and fatigued muscle function. The in vivo force measurement systems, buckle transducer technique and optic fiber technique, have revealed that, as compared to a pure concentric action, a non-fatiguing SSC exercise demonstrates considerable performance enhancement with increased force at a given shortening velocity. Characteristic to this phenomenon is very low EMG-activity in the concentric phase of the cycle, but a very pronounced contribution of the short-latency stretch-reflex component. This reflex contributes significantly to force generation during the transition (stretch-shortening) phase in SSC action such as hopping and running. The amplitude of the stretch reflex component - and the subsequent force enhancement - may vary according to the increased stretch-load but also to the level of fatigue. While moderate SSC fatigue may result in slight potentiation, the exhaustive SSC fatigue can dramatically reduce the same reflex contribution. SSC fatigue is a useful model to study the processes of reversible muscle damage and how they interact with muscle mechanics, joint and muscle stiffness. All these parameters and their reduction during SSC fatigue changes stiffness regulation through direct influences on muscle spindle (disfacilitation), and by activating III and IV afferent nerve endings (proprioseptic inhibition). The resulting reduced stretch reflex sensitivity and muscle stiffness deteriorate the force potentiation mechanisms. Recovery of these processes is long lasting and follows the bimodal trend of recovery. Direct mechanical disturbances in the sarcomere structural proteins, such as titin, may also occur as a result of an exhaustive SSC exercise bout.
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The aim of this study was to examine the effects of branched-chain amino acid (BCAA) supplementation on serum indicators of muscle damage after prolonged exercise. We hypothesized that BCAA supplementation would reduce the serum activities of intramuscular enzymes associated with muscle damage. To test this hypothesis, sixteen male subjects were assigned to one of two groups: the supplemental group (consuming 12 g x d(-1) BCAA for 14 d in addition to their normal diet) or the control group (normal diet only). Baseline serum creatine kinase (CK) and lactate dehydrogenase (LDH), shown to be accurate indicators of muscle damage, were determined during the week before the exercise test. The exercise test was administered on day seven and required the subjects to cycle for 120 min on an ergometer at approximately 70% VO2max. Blood samples were taken prior to and immediately following exercise and at 1 hr, 2 hrs, 3 hrs, 4 hrs, 1 d, 3 d, 5 d and 7 d postexercise. All subjects were required have their diets analyzed daily during the 14 d. Dietary analyses indicated that all subjects consumed the recommended daily intake of BCAA (0.64 g x kg(-1)) in their normal diets. Baseline serum values for CK and LDH were not different between groups in the 7 d prior to the test (p>0.05). However there were significant increases (p<0.05) between the pre-exercise and postexercise values for LDH and CK until 5 d postexercise test. Importantly, the BCAA supplementation significantly reduced this change in LDH from 2hrs to 5 d posttest, and CK from 4 hrs to 5 d post-test (p<0.05). These results indicate that supplementary BCAA decreased serum concentrations of the intramuscular enzymes CK and LDH following prolonged exercise, even when the recommended intake of BCAA was being consumed. This observation suggests that BCAA supplementation may reduce the muscle damage associated with endurance exercise.
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The plasma concentration of an amino acid (AA) is the result of its rates of appearance (Ra) in and disappearance (Rd) from plasma. As for most nutrients, AA Ra and Rd are tightly regulated and at the postabsorptive state Ra equals Rd. Factors controlling Ra are protein intake and tissue release; those controlling Rd are tissue uptake and body losses (urine, sweat, etc.). Regulation of plasma AA concentrations involves hormones, in particular insulin and glucagon, both of which induce hypoaminoacidemia (but for quite different reasons), and cortisol, which induces hyperaminoacidemia. In addition, in pathologic states, catecholamines, thyroid hormones, and cytokines modulate plasma AA levels. Peripheral availability of AAs after protein ingestion is controlled by the liver, with an activation of ureagenesis in hyperprotein feeding and repression during a hypoprotein diet. The arginine-to-citrulline pathway in the intestine plays a key role in this adaptative process. In some circumstances tissue uptake of AAs and further metabolism depend on plasma AA concentrations. Plasma glutamine level may be the driving force controlling the flux of this AA at the muscle level. Also, channeling of the arginine cellular pathways means that plasma arginine is a major controlling component of nitric oxide synthesis in endothelial and immune cells. All these features explain the excessive increase in glutamine and arginine demands, in particular for energy expenditure, leading to morbidity (e.g., gut atrophy, muscle wasting, and immune dysfunction) in stressed patients. Normoaminoacidemia is not synonymous with health because this state is observed in level 2 starvation (Ra and Rd decrease) or after minor injury (Ra and Rd increase). Hyperaminoacidemia may be the consequence of organ failure (Rd decreases) or excessive AA intake during parenteral nutrition (Ra increases). Hypoaminoacidemia is observed after organ removal (Ra decreases, e.g., decrease in citrulline concentration in short bowel syndrome) or in stress situations (Rd increases). Mere determinations of plasma AA concentrations at the basal state (i.e., postabsorptive) provide rather limited information. Their usefulness can be improved by measuring arteriovenous differences or performing time course measurements, but techniques based on stable isotopes are necessary to obtain more precise information on the behavior of a particular AA or group of AAs.
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Various experimental studies conducted in the 1970s demonstrated, at least in the physiological situation, the anabolic and/or anticatabolic properties of branched-chain amino acids (leucine, valine, isoleucine) or their ketoacid derivatives. This led to several clinical studies in the late 1970s and early 1980s that aimed to evaluate the potential benefits of BCAA supplementation in nutritional support of the critically ill. The data on burn, trauma, and sepsis are, however, far from convincing. Besides significant discrepancies in their results and the fact that most of these studies involved very small populations of patients, few of them meet the current standards of therapeutic evaluation. However, some positive results in specific studies suggest that the underlying concept may be correct but that interpretation has been faulty. Indeed, we know now that while the BCAAs possess regulatory properties on protein metabolism, leucine is by far the most potent, while isoleucine and valine are inefficient. However, in the above-mentioned studies, BCAA-supplemented nutrition very frequently supplied almost equivalent amounts of all 3 BCAAs. Moreover, several studies were performed without adequate basal nutritional support, which most probably hampered the correct metabolic utilization of these amino acids. Taken together, these factors mean that the demonstrations of BCAA efficacy were fortunate in the least. In contrast, more recently, leucine was demonstrated to positively affect protein synthesis in an experimental model of sepsis or burn. In parallel, 2 prospective controlled trials of BCAA supplementation in septic patients also demonstrated an improvement in patients' nutritional status and outcome. Thus, we should abandon the concept of BCAA-supplemented nutrition for a more promising leucine-supplemented nutrition that requires further evaluation.
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BCAAs (leucine, isoleucine, and valine), particularly leucine, have anabolic effects on protein metabolism by increasing the rate of protein synthesis and decreasing the rate of protein degradation in resting human muscle. Also, during recovery from endurance exercise, BCAAs were found to have anabolic effects in human muscle. These effects are likely to be mediated through changes in signaling pathways controlling protein synthesis. This involves phosphorylation of the mammalian target of rapamycin (mTOR) and sequential activation of 70-kD S6 protein kinase (p70 S6 kinase) and the eukaryotic initiation factor 4E-binding protein 1. Activation of p70 S6 kinase, and subsequent phopsphorylation of the ribosomal protein S6, is associated with enhanced translation of specific mRNAs. When BCAAs were supplied to subjects during and after one session of quadriceps muscle resistance exercise, an increase in mTOR, p70 S6 kinase, and S6 phosphorylation was found in the recovery period after the exercise with no effect of BCAAs on Akt or glycogen synthase kinase 3 (GSK-3) phosphorylation. Exercise without BCAA intake led to a partial phosphorylation of p70 S6 kinase without activating the enzyme, a decrease in Akt phosphorylation, and no change in GSK-3. It has previously been shown that leucine infusion increases p70 S6 kinase phosphorylation in an Akt-independent manner in resting subjects; however, a relation between mTOR and p70 S6 kinase has not been reported previously. The results suggest that BCAAs activate mTOR and p70 S6 kinase in human muscle in the recovery period after exercise and that GSK-3 is not involved in the anabolic action of BCAAs on human muscle.