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The purpose of this study was to utilize a rodent model to test the hypothesis that creatine (Cr) supplementation during resistance training would influence the pattern of slow-twitch muscle myosin heavy chain (MHC) isoforms expression. Male Wistar rats (2-3 months old, 250-300 g) were divided into 4 groups: Nontrained without creatine supplementat...
Contexts in source publication
Context 1
... and TRCR groups were submitted to a high-intensity resistance training program for 5 weeks (5 days/week), similar to that described by Cunha et al. (7) (Table 1). Before the initial training program, animals performed a 1-week pretraining (once a day) to familiarize them with the water and exercise. ...
Context 2
... adaptation protocol consisted of increasing the number of sets (2 to 4) and repetitions (5 to 10) with 40-second rests between each set, carrying an overload of 50% body weight strapped to a vest on the animal's chest (Figure 1). After the adaptation period, TR and TRCR groups began the resistance training program, which consisted of 4 sets of 10 jumps with overload equivalent to 50% body weight (first and second weeks), 60% (third and fourth weeks), and 70% (fifth wk), respectively (Table 1). Sessions were performed between 2 and 3 pm. ...
Citations
... Combinations between exercise training and creatine interventions resulted in greater lean mass and lower muscle protein catabolism [10,11]. Another possible effect of creatine supplementation is the adaptive modulation of myosin heavy chain (MyHC) isoforms in skeletal muscle fibers [12][13][14][15][16]. MyHC isoform profiles determine the muscle fiber phenotype; in general, predominantly MyHC I fibers have greater slow twitchoxidative characteristics, while fibers containing more MyHC II mostly have a fast glycolytic metabolism [17,18]. ...
Creatine has been used to maximize resistance training effects on skeletal muscles, including muscle hypertrophy and fiber type changes. This study aimed to evaluate the impact of creatine supplementation on the myostatin pathway and myosin heavy chain (MyHC) isoforms in the slow- and fast-twitch muscles of resistance-trained rats. Twenty-eight male Wistar rats were divided into four groups: a sedentary control (Cc), sedentary creatine supplementation (Cr), resistance training (Tc), and resistance training combined with creatine supplementation (Tcr). Cc and Tc received standard commercial chow; Cr and Tcr received a 2% creatine-supplemented diet. Tc and Tcr performed a resistance training protocol on a ladder for 12 weeks. Morphology, MyHC isoforms, myostatin, follistatin, and ActRIIB protein expressions were analyzed in soleus and white gastrocnemius portion samples. The results were analyzed using two-way ANOVA and Tukey’s test. Tc and Tcr exhibited higher performance than their control counterparts. Resistance training increased the ratio between muscle and body weight, the cross-sectional area, as well as the interstitial collagen fraction. Resistance training alone increased MyHC IIx and follistatin while reducing myostatin (p < 0.001) and ActRIIB (p = 0.040) expressions in the gastrocnemius. Resistance training induced skeletal muscle hypertrophy and interstitial remodeling, which are more evident in the gastrocnemius muscle. The effects were not impacted by creatine supplementation.
... In mice, creatine increases muscle protein content by phosphorylating serine/threonine kinase (protein kinase B, Akt), the target of rapamycin (TOR), and ribosome S6 protein kinase (P70 S6K ) (14) . In rats, creatine transforms MyHCII myofibers to MyHCI (15) myofibers by regulating myogenic regulatory factors (MRFs) (10) . The creatine-induced myofiber transformation is mediated by the AMPK/PGC-1α (AMP activated protein kinase/peroxisome proliferator-activated receptor-γ coactlvator-1α) (16) and TOR pathways (17) . ...
... MyHC II mRNA levels in rat muscle (15) and L. vannamei (13) . In our study, fMyHC s30 and fMyHC s10 in the slow skeletal muscle increased while fMyHCs and fMyHCc in the fast skeletal muscle decreased with increasing creatine supplementation. ...
To assess the role of dietary creatine on myofiber characteristics and protein synthesis in muscle, we fed grass carp ( Ctenopharyngodon idellus , initial body weight: 88.47 ± 1.44 g) creatine-supplemented diets (1.84, 5.91, 8.48, and 15.44 g/kg diet) for 8 weeks. Creatine supplementation did not affect growth performance, but significantly increased creatine contents in muscle and liver. At 8.48 g/kg, creatine decreased the activities of alanine transaminase and aspartate aminotransferase in serum, and improved hardness and chewiness of muscle due to shorter myofiber mean diameter, higher myofiber density and the frequencies of the diameters of class I and III and collagen content, longer sarcomere length, and upregulated mRNA levels of slow myosin heavy chains . Creatine supplementation upregulated the mRNA expressions of myogenic regulatory factors. The 8.48 g/kg creatine-supplemented diet significantly increased the contents of protein, total amino acids (AAs), essential AAs, and free flavor AAs in muscle, the protein levels of insulin-like growth factor I, myogenic differentiation antigen, and peroxisome proliferator-activated receptor-γ coactlvator-1α in muscle, and stimulated the phosphorylation of target of rapamycin (TOR) pathway in muscle. In summary, 8.48 mg/kg creatine improved fish health and skeletal muscle growth, and increased hardness and protein synthesis in muscle of grass carp by affecting myofiber characteristics and the TOR signaling pathway. A second-order regression model revealed that the optimal dietary creatine supplementation of grass carp ranges between 8.48 and 12.04 g/kg.
... Mice in this study were fed ad libitum; however, other studies using the same training model failed to reveal significant food intake differences. (25,26) Potential mechanisms underlying body mass and adiposity index reduction associated with strength and hypertrophy training (muscular resistance training) have been suggested, particularly due to muscle mass gain leading to higher basal metabolic rate and finally to body fat loss. (27) Further studies are warranted to investigate this topic. ...
Objective:
To evaluate the effect of three types of muscular resistance training on adiposity, inflammation levels and insulin activity in Swiss mice with fat-rich diet-induced obesity.
Methods:
Lean and obese male Swiss mice were selected and allocated to one of eight groups comprising eight mice each, as follows: standard diet + no training; standard diet + muscular resistance training; standard diet + hypertrophy training; standard diet + strength training; high-fat diet + no training; high-fat diet + muscular resistance training; high-fat diet + hypertrophy training; high-fat diet + strength training. The training protocol consisted of stair climbing for a 10-week period. Blood samples were collected for lactate analysis, glucose level measurement and insulin tolerance test. After euthanasia, adipose tissues were removed and weighed for adiposity index determination. Fragments of epididymal adipose tissue were then embedded for histological analysis or homogenized for tumor necrosis factor alpha level determination using the ELISA method.
Results:
Ausency of differences in total training volume and blood lactate levels overall emphasize the similarity between the different resistance training protocols. Body weight loss, reduced adipocyte area and lower adiposity index were observed in trained obese mice, regardless of training modality. Different training protocols also improved insulin sensitivity and reduced inflammation levels.
Conclusion:
Resistance training protocols were equally effective in reducing body fat, inflammation levels and insulin resistance in obese mice.
... We hypothesized that EDL responses induced by jump-training after 5 weeks would be related to higher plasma corticosterone levels observed in the same week (Figure 2(b)), as there is a strong correlation between glucocorticoids and protein muscle catabolism (Pereira & Freire de Carvalho, 2011;Schakman, Gilson, & Thissen, 2008). However, Aguiar et al. demonstrated that jump-training did not elicit changes in SOL weight and SOL weight/body weight ratio, which might be related to longer rest interval used in the study (40 s) (Aguiar et al., 2010). By contrast, climbing a ladder (Hornberger & Farrar, 2004) and squat-training (Tamaki, Uchiyama, & Nakano, 1992) have been shown to induce muscle hypertrophy in rats. ...
... Indeed, both reduction in MHC-I and increases in MHC-IIA contents were seen after 5 weeks in SOL muscle of trained rats (Figure 4(a,b)), which are in accordance with others using endurance training (Demirel et al., 1999). In addition, RT increased MHC-IIA in SOL muscle of rats (Aguiar et al., 2010). SOL muscle has been shown to be highly recruited after jump-training, as supported by others (Aguiar et al., 2010). ...
... In addition, RT increased MHC-IIA in SOL muscle of rats (Aguiar et al., 2010). SOL muscle has been shown to be highly recruited after jump-training, as supported by others (Aguiar et al., 2010). However, no differences were found in MHC contents of EDL muscle (Figure 5(a-d)). ...
Skeletal muscle hypertrophy is an exercise-induced adaptation, particularly in resistance training (RT) programs that use large volumes and low loads. However, evidence regarding the role of rest intervals on metabolic stress and muscular adaptations is inconclusive. Thus, we aimed to investigate the effects of a strenuous RT model (jump-training) on skeletal muscle adaptations and metabolic stress, considering the scarce information about RT models for rats. We hypothesized that jump-training induces metabolic stress and influences negatively the growth of soleus (SOL) and extensor digitorum longus (EDL) muscles of rats. Male Wistar rats (aged 60 days) were randomly assigned to non-trained or trained groups (n = 8/group). Trained rats performed jump-training during 5 days a week for 1, 3, or 5 weeks with 30 s of inter-set rest intervals. Forty-eight hours after the experimental period, rats were euthanized and blood samples immediately drawn to measure creatine kinase activity, lactate and corticosterone concentrations. Muscle weight-to-body weight ratio (MW/BW), cross-sectional area (CSA) and myosin heavy chain (MHC) isoform expression were determined. Higher lactate levels occurred after 20 min of training in weeks 1 and 3. Corticosterone levels were higher after 5 weeks of training. Jump-training had negative effects on hypertrophy of types-I and II muscle fibers after 5 weeks of training, as evidenced by decreased CSA and reduced muscle weight. Our results demonstrated that pronounced metabolic stress and impairment of muscle growth might take place when variables of exercise training are not appropriately manipulated.
Lay summary
Resistance training (RT) has been used to increase muscle mass. In this regard, training variables (intensity, volume, and frequency) must be strictly controlled in order to evoke substantial muscular fitness. This study shows that rats submitted to 5 weeks of intensive resistance jump-training – high intensity, large volume, and short rest intervals – present high levels of blood corticosterone associated with negative effects on hypertrophy of types-I and II muscle fibers.
... Numerous studies have confirmed that supplementation with CR in conjunction with programmed resistance training is effective for augmenting gains in body and fat-free mass, and muscular strength in both men and women [42][43][44][45]. These benefits are possibly due to enhanced training-induced increases in satellite cell number and myonuclei concentration within skeletal muscle fibers [46]. ...
The myoprotective effects of creatine monohydrate (CR) and whey protein (WP) are equivocal, with the use of proxy measures of muscle damage making interpretation of their effectiveness limited. The purpose of the study was to determine the effects of CR and WP supplementation on muscle damage and recovery following controlled, chemically-induced muscle damage. Degeneration of the extensor digitorum longus (EDL) muscle was induced by bupivacaine in rats supplemented with either CR, WP, or standard rat chow (CON). At day 7 and 14 post-myotoxic injury, injured EDL muscles were surgically removed and tested for isometric contractile properties, followed by the contralateral, non-injured EDL muscle. At the completion of testing, muscles were snap-frozen in liquid nitrogen and stored for later analysis. Data were analyzed using analysis of variance. Creatine-supplemented muscles displayed a greater proportion of non-damaged (intact) fibers (p = 0.002) and larger cross-sectional areas of regenerating and non-damaged fibers (p = 0.024) compared to CON muscles at day 7 post-injury. At day 14 post-injury, CR-supplemented muscles generated higher absolute forces concomitant with greater contractile protein levels compared to CON (p = 0.001, p = 0.008) and WP-supplemented muscles (p = 0.003, p = 0.006). Creatine supplementation appears to offer an element of myoprotection which was not observed following whey protein supplementation.
... We do not know whether resistance exercise would decrease responding maintained by other (i.e., nondrug) stimuli. Unlike aerobic exercise, which generally increases food intake to compensate for increased caloric expenditure (Novak et al. 2012), resistance exercise typically decreases (Aguiar et al. 2010;Aparicio et al. 2011) or does not alter (Duarte et al. 2017;Ebal et al. 2007;Haraguchi et al. 2014) food intake. Resistance exercise did not decrease responding maintained by food during lever-press training, but all subjects were food restricted during this time and the maximal number of food reinforcers was limited to 40. ...
Rationale:
Preclinical studies consistently report that aerobic exercise decreases drug self-administration and other forms of drug-seeking behavior; however, relatively few studies have examined other types of physical activity.
Objectives:
The purpose of the present study was to examine the effects of resistance exercise (i.e., strength training) on heroin self-administration and mRNA expression of genes known to mediate opioid reinforcement and addictive behavior in the nucleus accumbens (NAc) of heroin-exposed rats.
Methods:
Female rats were obtained during late adolescence and divided into two groups. Resistance exercise rats were trained to climb a vertical ladder wearing a weighted vest; sedentary control rats were placed repeatedly on the ladder oriented horizontally on its side. All rats were implanted with intravenous catheters and trained to self-administer heroin on a fixed ratio (FR1) schedule of reinforcement. mRNA expression in the NAc core and shell was examined following behavioral testing.
Results:
Resistance exercise significantly decreased heroin self-administration, resulting in a downward shift in the dose-effect curve. Resistance exercise also reduced mRNA expression for mu opioid receptors and dopamine D1, D2, and D3 receptors in the NAc core. Resistance exercise increased mRNA expression of dopamine D5 receptors in the NAc shell and increased mRNA expression of brain-derived neurotrophic factor (exons I, IIB, IIC, IV, VI, IX) in the NAc core.
Conclusions:
These data indicate that resistance exercise decreases the positive reinforcing effects of heroin and produces changes in opioid and dopamine systems in the NAc of heroin-exposed rats.
... If they work well, these fibers can act in the removal process of this muscle lactic acid produced by fasttwitch fibers through absorption and use of lactate as an energy source. Supplementation with exercise can increase the aerobic capacity of these slow-twitch fibers, (AGUIAR et al., 2010) which suggests a potential influence of this mechanism in the values expressed by the C280+exerc groups ( Figure 8). As they are not recruited in maximum efforts (as in tetany), these fibers can maintain their functions without the interference of lesions or alterations in their membrane. ...
The aim of the present study was to investigate the effects of different doses of oral creatine supplementation on tibial muscle resistance and fatigue in Wistar rats. The treatment protocols included swimming exercises, supplementation alone (different doses), and supplementation (different doses) + swimming exercises. Analysis of the effect of creatine supplementation on skeletal muscle fatigue was performed using the intensity of muscle contraction to electrical stimulation to evaluate the intensity of muscle contraction, decay time of muscle tetanic contraction to 50% of maximum tension (fatigue), and the area under the curve for the intensity x time ratio, besides AST, LDH, and urea plasmatic analysis. Our results suggest that creatine supplementation seems to be able to produce ergogenic effects on contractile metabolism in the group treated with the dose of 280 mg/kg + swim exercise. This creatine dose presented a statistically significant increase in decay time of muscle tetanic contraction (C280+swim (119±13.1), C500+swim (110±23.6) and C1000+swim (87±15.1)), area under the curve between tetanic contractions, and plasma LDH decrease, when compared to the other doses. These data clearly demonstrate that high doses do not lead to any additional ergogenic effects. We conclude that the dose of 280 mg/kg+swim exercise obtained the best ergogenic effects on tibial muscle resistance and fatigue in Wistar rats. © 2017, Universidade Federal de Uberlandia. All rights reserved.
... If they work well, these fibers can act in the removal process of this muscle lactic acid produced by fast-twitch fibers through absorption and use of lactate as an energy source. Supplementation with exercise can increase the aerobic capacity of these slow-twitch fibers, (AGUIAR et al., 2010) which suggests a potential influence of this mechanism in the values expressed by the C280+exerc groups (figure 8). As they are not recruited in maximum efforts (as in tetany), these fibers can maintain their functions without the interference of lesions or alterations in their membrane. ...
The aim of the present study was to investigate the effects of different doses of oral creatine supplementation on tibial muscle resistance and fatigue in Wistar rats. The treatment protocols included swimming exercises, supplementation alone (different doses), and supplementation (different doses) + swimming exercises. Analysis of the effect of creatine supplementation on skeletal muscle fatigue was performed using the intensity of muscle contraction to electrical stimulation to evaluate the intensity of muscle contraction, decay time of muscle tetanic contraction to 50% of maximum tension (fatigue), and the area under the curve for the intensity x time ratio, besides AST, LDH, and urea plasmatic analysis. Our results suggest that creatine supplementation seems to be able to produce ergogenic effects on contractile metabolism in the group treated with the dose of 280 mg/kg + swim exercise. This creatine dose presented a statistically significant increase in decay time of muscle tetanic contraction (C280+swim (119±13.1), C500+swim (110±23.6) and C1000+swim (87±15.1)), area under the curve between tetanic contractions, and plasma LDH decrease, when compared to the other doses. These data clearly demonstrate that high doses do not lead to any additional ergogenic effects. We conclude that the dose of 280 mg/kg+swim exercise obtained the best ergogenic effects on tibial muscle resistance and fatigue in Wistar rats. Resumo O objetivo do presente estudo foi investigar os efeitos de diferentes doses de suplementação oral de creatina sobre a resistência e fadiga do músculo tibial em ratos wistar. Os protocolos de tratamento incluíram exercícios de natação, suplementação isolada (doses diferentes) e suplementação (doses diferentes) + exercícios de natação. A análise do efeito da suplementação de creatina na fadiga do músculo esquelético foi realizada utilizando-se a intensidade da contração muscular à uma estimulação elétrica, aferindo a intensidade da contração muscular, tempo de decaimento da contração tetânica do músculo a 50% da tensão máxima (fadiga) e a área sob a curva para a razão de intensidade x tempo, além de análises plasmática de AST, LDH e ureia. Nossos resultados sugerem que a suplementação de creatina parece ser capaz de produzir efeitos ergogênicos no metabolismo contrátil no grupo tratado, com a dose de 280 mg/kg+natação. Esta dose de creatina teve um aumento estatisticamente significativo no tempo de decaimento da contracção tetânica muscular (C280+natação (119±13.1), C500+natação (110±23.6) e C1000+natação (87±15.1)), área sob a curva entre as contrações tetânicas e também diminuição da LDH plasmática quando comparada com as outras doses. Estes dados demonstraram claramente que doses elevadas não conduzem a qualquer aumento adicional de efeitos ergogênicos. Concluimos que a dose de 280 mg / kg + exercício de natação obteve os melhores efeitos ergogênicos sobre a resistência e fadiga do músculo tibial em ratos wistar. Palavras-chave: creatina: exercício: fadiga: contração tetânica: suplemento dietético
... One aim of this study was to adapt a model of resistance exercise that would be suitable for drug abuse research but that minimized exposure to painful or stressful stimuli. Consequently, we avoided the use of electric shock and water submersion, both of which are often employed in animal models of resistance exercise (e.g., Aguiar et al., 2010;Fluckey et al., 2002;Hornberger and Farrar, 2004;Soufi et al., 2011;Tamaki et al., 1992). Similar to previous studies, we used ladder climbing to induce muscle hypertrophy; however, we avoided the use of electric shock and other painful stimuli in a manner similar to that recently described by Nokia and colleagues (2016). ...
Background:
Exercise is associated with positive outcomes in drug abusing populations and reduces drug self-administration in laboratory animals. To date, most research has focused on aerobic exercise, and other types of exercise have not been examined. This study examined the effects of resistance exercise (strength training) on cocaine self-administration and BDNF expression, a marker of neuronal activation regulated by aerobic exercise.
Methods:
Female rats were assigned to either exercising or sedentary conditions. Exercising rats climbed a ladder wearing a weighted vest and trained six days/week. Training consisted of a three-set "pyramid" in which the number of repetitions and resistance varied across three sets: eight climbs carrying 70% body weight (BW), six climbs carrying 85% BW, and four climbs carrying 100% BW. Rats were implanted with intravenous catheters and cocaine self-administration was examined. Behavioral economic measures of demand intensity and demand elasticity were derived from the behavioral data. BDNF mRNA expression was measured via qRT-PCR in the nucleus accumbens following behavioral testing.
Results:
Exercising rats self-administered significantly less cocaine than sedentary rats. A behavioral economic analysis revealed that exercise increased demand elasticity for cocaine, reducing consumption at higher unit prices. Exercising rats had lower BDNF expression in the nucleus accumbens core than sedentary rats.
Conclusions:
These data indicate that resistance exercise decreases cocaine self-administration and reduces BDNF expression in the nucleus accumbens after a history of cocaine exposure. Collectively, these findings suggest that strength training reduces the positive reinforcing effects of cocaine and may decrease cocaine use in human populations.
... Rodents can perform standing upright and lengthening their hindlimbs (i.e., soleus and extensor digitorum longus) while weight is loaded (65~75 % of one RM) to a belt, vest, or shoulder harness (Fig. 2a andTable 2). In this model [2, 5, 47, 80, 88, 132], electric shock may be applied to the tail to motivate lifting [30, 88]. This type of exercise model or its mimics approximates human weight lifting (squat type). ...
Exercise and physical activity function as a patho-physiological process that can prevent, manage, and regulate numerous chronic conditions, including metabolic syndrome and age-related sarcopenia. Because of research ethics and technical difficulties in humans, exercise models using animals are requisite for the future development of exercise mimetics to treat such abnormalities. Moreover, the beneficial or adverse outcomes of a new regime or exercise intervention in the treatment of a specific condition should be tested prior to implementation in a clinical setting. In rodents, treadmill running (or swimming) and ladder climbing are widely used as aerobic and anaerobic exercise models, respectively. However, exercise models are not limited to these types. Indeed, there are no golden standard exercise modes or protocols for managing or improving health status since the types (aerobic vs. anaerobic), time (morning vs. evening), and duration (continuous vs. acute bouts) of exercise are the critical determinants for achieving expected beneficial effects. To provide insight into the understanding of exercise and exercise physiology, we have summarized current animal exercise models largely based on aerobic and anaerobic criteria. Additionally, specialized exercise models that have been developed for testing the effect of exercise on specific physiological conditions are presented. Finally, we provide suggestions and/or considerations for developing a new regime for an exercise model.
