Postactivation Potentiation Improves Acute Resistance Exercise Performance and Muscular Force in Trained Men.

ABSTRACT: Conrado de Freitas, M, Rossi, FE, Colognesi, LA, de Oliveira, JVNS, Zanchi, NE, Lira, FS, Cholewa, JM, and Gobbo, LA. Postactivation potentiation improves acute resistance exercise performance and muscular force in trained men. J Strength Cond Res 35(5): 1357-1363, 2021-The purpose of this study was to investigate the effects of heavy back squat (90% one repetition maximum [1RM]) postactivation potentiation (PAP) on acute resistance exercise performance and force production in recreationally trained men, and to verify the relationship between maximal strength and the PAP response. Ten resistance-trained men randomly completed 4 experimental trials: (a) back squats without PAP (No-PAP), (b) back squats with PAP, (c) maximum voluntary isometric contraction (MVIC) of the quadriceps without PAP, and (d) MVIC with PAP. Back squats were performed with 4 sets at 70% of 1 RM with 2 minutes of rest interval. The number of squats repetitions performed was recorded for each set, and a total number of repetitions were calculated to analyze performance. Maximum voluntary isometric contraction was measured using electronic dynamometer, and the peak force and mean force were recorded. Blood lactate concentration was analyzed presquat and postsquat exercise. Repetitions performed in the first set was significantly (p < 0.001) greater in the PAP condition (22.00 ± 5.14) compared with No-PAP (15.50 ± 5.10), which resulted in significantly (p = 0.001) more total repetitions performed in the PAP (56.20 ± 17.3) condition compared with No-PAP (48.80 ± 14.5). Maximum voluntary isometric contraction peak was higher in PAP than in No-PAP (PAP = 765.7 ± 147.8 vs. No-PAP = 696.8 ± 131.5 N, p = 0.006). No significant correlations were observed between back squat 1RM relative to body mass and the PAP response in squat and MVIC. There were no significant differences in lactate concentration between conditions. In conclusion, PAP resulting from a heavy load prior back squat exercise improved total volume during resistance exercise. In addition, PAP was effective to increase force production during MVIC, but there was no relationship between relative 1RM values and the PAP response in trained men.

Appetite Is Suppressed After Full-Body Resistance Exercise Compared With Split-Body Resistance Exercise: The Potential Influence of Lactate and Autonomic Modulation.

ABSTRACT: Conrado de Freitas, M, Ricci-Vitor, AL, de Oliveira, JVNS, Quizzini, GH, Vanderlei, LCM, Silva, BSA, Zanchi, NE, Cholewa, JM, Lira, FS, and Rossi, FE. Appetite is suppressed after full-body resistance exercise compared with split-body resistance exercise: the potential influence of lactate and autonomic modulation. J Strength Cond Res 35(9): 2532-2540, 2021-The purposes of this study were to investigate the effects of full- vs. split-body resistance training on appetite and leptin response and to verify the potential involvement of lactate and autonomic modulation during this response in trained men. Twelve recreationally resistance-trained men (age = 26.1 ± 5.5 years) performed 3 randomized trials in 3 conditions: upper body (UB), lower body (LB), and full body (FB). The subjective rating of hunger was obtained through a visual analog scale. Leptin and lactate concentration were evaluated at rest, immediately after exercise, and during recovery. Heart rate variability in the time and frequency domains was recorded at baseline and during recovery (until 60 minutes after exercise) to assess autonomic modulation. The FB condition induced lower subjective hunger ratings than the UB at Post-1 hour (p < 0.05) and a significant difference in the area under the curve between conditions (p = 0.028) with lower hunger sensation for FB in relation to UB (p = 0.041). The FB presented greater lactate concentration and induced slower heart rate variability recovery in relation to UB and LB conditions (p < 0.05), and heart rate variability remained lower until 60 minutes after exercise compared with rest only in the FB condition. There was a significant negative correlation between subjective hunger ratings and lactate concentration only for the FB condition (r = -0.72, p = 0.028). Full-body resistance exercise induced lower subjective hunger ratings after exercise in relation to UB resistance exercise. The FB also induced higher lactate production and slower recovery of autonomic modulation compared with the UB and LB conditions. Future research is necessary to investigate a mechanistic relationship between lactate concentrations and hunger suppression after resistance exercise.

Dietary proteins and amino acids in the control of the muscle mass during immobilization and aging: role of the MPS response.

Dietary proteins/essential amino acids (EAAs) are nutrients with anabolic properties that may increase muscle mass or attenuate muscle loss during immobilization and aging via the stimulation of muscle protein synthesis (MPS). An EAA's anabolic threshold, capable to maximize the stimulation of MPS has been hypothesized, but during certain conditions associated with muscle loss, this anabolic threshold seems to increase which reduces the efficacy of dietary EAAs to stimulate MPS. Preliminary studies have demonstrated that acute ingestion of dietary proteins/EAA (with a sufficient amount of leucine) was capable to restore the postprandial MPS during bed rest, immobilization or aging; however, whether these improvements translate into chronic increases (or attenuates loss) of muscle mass is equivocal. For example, although free leucine supplementation acutely increases MPS and muscle mass in some chronic studies, other studies have reported no increases in muscle mass following chronic leucine supplementation. In contrast, chronically increasing leucine intake via the consumption of an overall increase in dietary protein appears to be the most effective dietary intervention toward increasing or attenuating lean mass during aging; however, more research investigating the optimal dose and timing of protein ingestion is necessary. Several studies have demonstrated that decreases in postprandial MPS as a result of increased circulating oxidative and inflammatory are more responsible than muscle protein breakdown for the decreases in muscle mass during disuse and health aging. Therefore, nutritional interventions that reduce oxidation or inflammation in conjunction with higher protein intakes that overcome the anabolic resistance may enhance the MPS response to feeding and either increase muscle mass or attenuate loss. In preliminary studies, antioxidant vitamins and amino acids with antioxidant or anti-inflammatory properties show potential to restore the anabolic response associated with protein ingestion. More research, however, is required to investigate if these nutrients translate to increases in MPS and, ultimately, increased lean mass in aging humans. The purpose of the present review is to discuss the role of protein/EAA intake to enhance postprandial MPS during conditions associated with muscle loss, and bring new perspectives and challenges associated nutritional interventions aimed to optimize the anabolic effects of dietary protein/EAAs ingestion.

Basic models modeling resistance training: an update for basic scientists interested in study skeletal muscle hypertrophy.

Human muscle hypertrophy brought about by voluntary exercise in laboratorial conditions is the most common way to study resistance exercise training, especially because of its reliability, stimulus control and easy application to resistance training exercise sessions at fitness centers. However, because of the complexity of blood factors and organs involved, invasive data is difficult to obtain in human exercise training studies due to the integration of several organs, including adipose tissue, liver, brain and skeletal muscle. In contrast, studying skeletal muscle remodeling in animal models are easier to perform as the organs can be easily obtained after euthanasia; however, not all models of resistance training in animals displays a robust capacity to hypertrophy the desired muscle. Moreover, some models of resistance training rely on voluntary effort, which complicates the results observed when animal models are employed since voluntary capacity is something theoretically impossible to measure in rodents. With this information in mind, we will review the modalities used to simulate resistance training in animals in order to present to investigators the benefits and risks of different animal models capable to provoke skeletal muscle hypertrophy. Our second objective is to help investigators analyze and select the experimental resistance training model that best promotes the research question and desired endpoints.

Effects of betaine on performance and body composition: a review of recent findings and potential mechanisms.

Betaine is a methyl derivative of glycine first isolated from sugar beets. Betaine consumed from food sources and through dietary supplements presents similar bioavailability and is metabolized to di-methylglycine and sarcosine in the liver. The ergogenic and clinical effects of betaine have been investigated with doses ranging from 500 to 9,000 mg/day. Some studies using animal models and human subjects suggest that betaine supplementation could promote adiposity reductions and/or lean mass gains. Moreover, previous investigations report positive effects of betaine on sports performance in both endurance- and resistance-type exercise, despite some conflicting results. The mechanisms underlying these effects are poorly understood, but could involve the stimulation of lipolysis and inhibition of lipogenesis via gene expression and subsequent activity of lipolytic-/lipogenic-related proteins, stimulation of autocrine/endocrine IGF-1 release and insulin receptor signaling pathways, stimulation of growth hormone secretion, increased creatine synthesis, increases in protein synthesis via intracellular hyper-hydration, as well as exerting psychological effects such as attenuating sensations of fatigue. However, the exact mechanisms behind betaine action and the long-term effects of supplementation on humans remain to be elucidated. This review aims to describe evidence for the use of betaine as an ergogenic and esthetic aid, and discuss the potential mechanisms underlying these effects.

Comparison of 8-weeks of full versus split body resistance training on appetite and energy intake in non-obese untrained men.

To investigate the effects of 8-weeks of full versus split body resistance training (RT) on appetite and energy intake in non-obese untrained men. The participants were pair-matched based on their initial fat mass and then randomly allocated into one of two treatment groups: Full body (FB, n = 20), in which all muscle groups were trained in every session, or Split body (SB, n = 15), in which upper and lower muscle groups were trained alternated per session; both groups trained in non-consecutive days, three times per week with total number of sets performed equated between groups. Energy intake, body composition, and strength performance were evaluated at pre-training, and after 8-weeks of RT, as well as self-reported hunger, fullness, and desire to eat, that were assessed at fasted and feed states pre- and post-intervention. FB and SB resistance training increased fat-free mass (FFM) (p < 0.001); and FB induced greater maximal strength improvement (p = 0.027). At fasted state self-reported hunger increased, and fullness decreased, while in feed state desire to eat something fatty increased in both groups. Carbohydrate intake (p = 0.011) decreased in both groups. In conclusion, FB and SB training increased orexigenic drive (increasing hunger and decreasing fullness), however, total energy intake and fat mass did not change after 8-weeks of RT in non-obese untrained men.Registered under Brazilian Registry of Clinical Trials no. RBR-3wkcvyw.

Creatine supplementation combined with blood flow restriction training enhances muscle thickness and performance: a randomized, placebo-controlled, and double-blind study.

This study aimed to compare the effects of an 8-week creatine (CR) or placebo (PL) supplementation on muscle strength, thickness, endurance, and body composition employing different training paradigms with blood flow restriction (BFR) vs. traditional resistance training (TRAD). Seventeen healthy males were randomized between the PL (n = 9) and CR (n = 8) groups. Participants were trained unilaterally utilizing a within-between subject bicep curl exercise where each arm was allocated to TRAD or BFR for 8 weeks. Muscular strength, thickness, endurance, and body composition were evaluated. Creatine supplementation promoted increases in muscle thickness in TRAD and BFR compared with their placebo counterparts, however, without a significant difference between treatments (p = 0.349). TRAD training increased maximum strength (1 repetition maximum (1RM)) compared with BFR after 8 weeks of training (p = 0.021). Repetitions to failure at 30% of 1RM were increased in the BFR-CR group compared with the TRAD-CR group (p = 0.004). Repetitions to failure at 70% 1RM were increased from weeks 0-4 (p < 0.05) and 4-8 (p < 0.05) in all groups. Creatine supplementation exerted a hypertrophic effect when utilized with TRAD and BFR paradigms and increased muscle performance at 30% 1RM when utilized in conjunction with BFR. Therefore, creatine supplementation seems to amplify muscle adaptation following a BFR program. Registered in the Brazilian Registry of Clinical Trials (ReBEC), under the registration number: RBR-3vh8zgj.

Does Beta-Alanine Supplementation Potentiate Muscle Performance Following 6 Weeks of Blood Flow Restriction or Traditional Resistance Training?

We aimed to compare the effects of beta-alanine on Traditional Resistance Training (TRAD) or Blood Flow Restriction Training (BFR). METHODS: 19 subjects were randomly allocated to a Placebo (n = 10) or beta-alanine (n = 9) group. Subjects from both groups were trained unilaterally (unilateral arm curl) for six weeks, and each arm was trained using a different paradigm (BFR or TRAD). One repetition maximum (1RM) test measurements were performed before and after the strength training program. Work output was accessed as the total weight lifted (repetitions × weight lifted × sets) for the entire strength training program. RESULTS: 1RM or total weight lifted was not increased by beta-alanine supplementation. However, the TRAD-trained arm showed a significantly increased 1RM and total weight lifted compared to the BFR arm (p < 0.05). CONCLUSION: We conclude that in the short-term (6 weeks) and following the current experimental conditions, beta-alanine does not benefit BFR or TRAD in terms of total weight lifted (volume of training) or maximal strength (1RM).

An experimental model for resistance exercise in rodents.

This study aimed to develop an equipment and system of resistance exercise (RE), based on squat-type exercise for rodents, with control of training variables. We developed an operant conditioning system composed of sound, light and feeding devices that allowed optimized RE performance by the animal. With this system, it is not necessary to impose fasting or electric shock for the animal to perform the task proposed (muscle contraction). Furthermore, it is possible to perform muscle function tests in vivo within the context of the exercise proposed and control variables such as intensity, volume (sets and repetitions), and exercise session length, rest interval between sets and repetitions, and concentric strength. Based on the experiments conducted, we demonstrated that the model proposed is able to perform more specific control of other RE variables, especially rest interval between sets and repetitions, and encourages the animal to exercise through short-term energy restriction and "disturbing" stimulus that do not promote alterations in body weight. Therefore, despite experimental limitations, we believe that this RE apparatus is closer to the physiological context observed in humans.

Renewed avenues through exercise muscle contractility and inflammatory status.

Physical inactivity leads to the accumulation of visceral fat and, consequently, to the activation of a network of inflammatory pathways which may promote development of insulin resistance, atherosclerosis, neurodegeneration, and tumour growth. These conditions belong to the "diseasome of physical inactivity". In contrast, the protective effect of regular exercise against diseases associated with chronic inflammation may to some extent be ascribed to an anti-inflammatory effect. The so called "acute exercise threshold", the complex mixture of several variables involved in exercise, such as type, volume, frequency, and intensity range is capable of inducing positive physiological adaptations and has been specifically addressed in the recent literature. The major concern is related to the level of the threshold: "exercise training shifts from a therapeutic adaptive intervention to one with potential pathological consequences". Nonetheless, if the mechanical stimulus is too weak to disrupt cellular homeostasis, training adaptations will not occur. Answering these questions could present practical applications, especially during inflammatory diseases associated with detrimental muscle effects and could theoretically constitute a "new" therapeutic approach to treat/improve an inflammatory state. This paper aims to describe specific data from the literature regarding the effects of exercise on inflammatory diseases in order to promote a more sophisticated perspective on the anti-inflammatory effects of exercise.

Role of MST1 in the regulation of autophagy and mitophagy: implications for aging-related diseases.

As a key mechanism to maintain cellular homeostasis under stress conditions, autophagy/mitophagy is related to the occurrence of metabolic disorders, neurodegenerative diseases, cancer, and other aging-related diseases, but the relevant signal pathways regulating autophagy have not been clarified. Mammalian sterile 20-like kinase 1 (MST1) is a central regulatory protein of many metabolic pathways involved in the pathophysiological processes of aging and aging-related diseases and has become a critical integrator affecting autophagic signaling. Recent studies show that MST1 not only suppresses autophagy through directly phosphorylating Beclin-1 and/or inhibiting the protein expression of silent information regulator 1 (SIRT1) in the cytoplasm, but also inhibits BCL2/adenovirus E1B protein-interacting protein 3 (BNIP3)-, FUN14 domain containing 1 (FUNDC1)-, and Parkin (Parkinson protein 2)-mediated mitophagy by interacting with factors such as Ras association domain family 1A (RASSF1A). Indeed, a common pharmacological strategy for anti-aging is to induce autophagy/mitophagy through MST1 inhibition. This article reviews the role and mechanism of MST1 in regulating autophagy during aging, to provide evidence for the development of drugs targeting MST1.

Acute Low-Dose Capsiate Supplementation Improves Upper Body Resistance Exercise Performance in Trained Men: A Randomized, Crossover and Double-Blind Study.

Objectives: The purpose of this study was to compare the effects of two acute doses of Capsiate (CAP; 6 vs. 12 mg) on upper body resistance exercise performance in trained men. Methods: Using a randomized, crossover and double-blind design, 20 resistance-trained males were supplemented with low-dose CAP (6 mg), high-dose CAP (12 mg) or placebo 45 minutes before exercise. Subjects performed 4 sets of bench press with repetitions to failure at 70% 1 repetition maximum (1RM) and 2 minutes of rest between each set. The ratings of perceived exertion (RPE) and blood lactate were analyzed at baseline and after exercise. Results: Total weight lifted was greater in the low CAP (2,454.6 ± 448.6 kg) compared to placebo (2,354.7 ± 458.6 kg, p = 0.039) and high CAP (2,309.3 ± 428.1 kg, p = 0.001). There was no significant difference between conditions for RPE (p = 0.155) and blood lactate (p = 0.434). Conclusion: In summary, 6 mg CAP increased total weight lifted and repetitions to failure on bench press exercise in trained men, while 12 mg did not present any effect.

HMB supplementation: clinical and athletic performance-related effects and mechanisms of action.

Amino acids such as leucine and its metabolite α-ketoisocaproate (KIC), are returning to be the focus of studies, mainly because of their anti-catabolic properties, through inhibition of muscle proteolysis and enhancement of protein synthesis. It is clear that these effects may counteract catabolic conditions, as well as enhance skeletal muscle mass and strength in athletes. Moreover, beta-hydroxy-beta-methylbutyrate (HMB) has been shown to produce an important effect in reducing muscle damage induced by mechanical stimuli of skeletal muscle. This review aims to describe the general scientific evidence of KIC and HMB supplementation clinical relevance, as well as their effects (e.g., increases in skeletal muscle mass and/or strength), associated with resistance training or other sports. Moreover, the possible mechanisms of cell signaling regulation leading to increases and/or sparing (during catabolic conditions) of skeletal muscle mass are discussed in detail based on the recent literature.

Exercise May Promote Skeletal Muscle Hypertrophy via Enhancing Leucine-Sensing: Preliminary Evidence.

Several studies have indicated a positive effect of exercise (especially resistance exercise) on the mTOR signaling that control muscle protein synthesis and muscle remodeling. However, the relationship between exercise, mTOR activation and leucine-sensing requires further clarification. Two month old Sprague-Dawley rats were subjected to aerobic exercise (treadmill running at 20 m/min, 6° incline for 60 min) and resistance exercise (incremental ladder climbing) for 4 weeks. The gastrocnemius muscles were removed for determination of muscle fibers diameter, cross-sectional area (CSA), protein concentration and proteins involved in muscle leucine-sensing and protein synthesis. The results show that 4 weeks of resistance exercise increased the diameter and CSA of gastrocnemius muscle fibers, protein concentration, the phosphorylation of mTOR (Ser2448), 4E-BP1(Thr37/46), p70S6K (Thr389), and the expression of LeuRS, while aerobic exercise just led to a significant increase in protein concentration and the phosphorylation of 4E-BP1(Thr37/46). Moreover, no difference was found for Sestrin2 expression between groups. The current study shows resistance exercise, but not aerobic exercise, may increase muscle protein synthesis and protein deposition, and induces muscle hypertrophy through LeuRS/mTOR signaling pathway. However, further studies are still warranted to clarify the exact effects of vary intensities and durations of aerobic exercise training.

Advances in the Role of Leucine-Sensing in the Regulation of Protein Synthesis in Aging Skeletal Muscle.

Skeletal muscle anabolic resistance (i.e., the decrease in muscle protein synthesis (MPS) in response to anabolic stimuli such as amino acids and exercise) has been identified as a major cause of age-related sarcopenia, to which blunted nutrition-sensing contributes. In recent years, it has been suggested that a leucine sensor may function as a rate-limiting factor in skeletal MPS via small-molecule GTPase. Leucine-sensing and response may therefore have important therapeutic potential in the steady regulation of protein metabolism in aging skeletal muscle. This paper systematically summarizes the three critical processes involved in the leucine-sensing and response process: (1) How the coincidence detector mammalian target of rapamycin complex 1 localizes on the surface of lysosome and how its crucial upstream regulators Rheb and RagB/RagD interact to modulate the leucine response; (2) how complexes such as Ragulator, GATOR, FLCN, and TSC control the nucleotide loading state of Rheb and RagB/RagD to modulate their functional activity; and (3) how the identified leucine sensor leucyl-tRNA synthetase (LARS) and stress response protein 2 (Sestrin2) participate in the leucine-sensing process and the activation of RagB/RagD. Finally, we discuss the potential mechanistic role of exercise and its interactions with leucine-sensing and anabolic responses.

Chronic capsiate supplementation increases fat-free mass and upper body strength but not the inflammatory response to resistance exercise in young untrained men: a randomized, placebo-controlled and double-blind study.

BACKGROUND: Acute capsaicinoid and capsinoid supplementation has endurance and resistance exercise benefits; however, if these short-term performance benefits translate into chronic benefits when combined with resistance training is currently unknown. This study investigated changes of chronic Capsiate supplementation on muscular adaptations, inflammatory response and performance in untrained men. METHODS: Twenty untrained men were randomized to ingest 12 mg Capsiate (CAP) or placebo in a parallel, double-blind design. Body composition and performance were measured at pre-training and after 6 weeks of resistance training. An acute resistance exercise session test was performed pre and post-intervention. Blood samples were collected at rest and post-resistance exercise to analyze Tumor necrosis factor- (TNF-), Soluble TNF- receptor (sTNF-r), Interleukin-6 (IL-6) and Interleukin-10 (IL-10). RESULTS: Exercise and CAP supplementation increased fat-free mass in comparison to baseline by 1.5 kg (P < 0.001), however, the majority of the increase (1.0 kg) resulted from an increase in total body water. The CAP change scores for fat-free mass were significantly greater in comparison to the placebo (CAP ∆%= 2.1 ± 1.8 %, PLA ∆%= 0.7 ± 1.3 %, P = 0.043) and there was a significant difference between groups in the bench press exercise (P = 0.034) with greater upper body strength change score for CAP (∆%= 13.4 ± 9.1 %) compared to placebo (∆%= 5.8 ± 5.2 %), P = 0.041. CAP had no effect on lower body strength and no supplementation interactions were observed for all cytokines in response to acute resistance exercise (P > 0.05). CONCLUSION: Chronic Capsiate supplementation combined with resistance training during short period (6 weeks) increased fat-free mass and upper body strength but not inflammatory response and performance in young untrained men.

Glucocorticoids: extensive physiological actions modulated through multiple mechanisms of gene regulation.

Glucocorticoid hormones are important regulators of several physiological processes. Despite having been initially named based on their role in glucose metabolism, glucocorticoids are also fundamental in the regulation of developmental, metabolic, and neurobiological processes, as well as several other biological functions. Due to their involvement in a diverse array of biological pathways, its wide spectrum of action, it is predicted that a wide range of genes may have their expression regulated by the activated glucocorticoid receptor (GR). In fact, it has been demonstrated that in addition to the regulation of several effectors genes, the expression of the gene encoding for GR itself is regulated by physiological stimuli and fine-tuning mechanisms. Importantly, such generalized effector responses and fine-tuning responses seem to be largely mediated by mechanisms of gene regulation. Therefore, this review aims to describe the mechanisms of gene regulation by glucocorticoid hormones, which are capable of regulating differential gene transcription, within a physiological context. From this discussion, we hope to shed light on how a single molecule that is capable of exerting such divergent effects is also capable of promoting such distinct responses in different target tissues.

Is acute supramaximal exercise capable of modulating lipoprotein profile in healthy men?

BACKGROUND: This study examined the effects of acute supramaximal exercise (approximately 115% VO(2max)) on the blood lipid profile for three different carbohydrate (CHO) storage levels (control, low and high). METHODS: Six male subjects were randomly divided into three different groups: control, low CHO and high CHO. These groups differed in the diet to which the subjects were submitted before each exercise session. The lipid profile [triglycerides (TG), very low-density lipoprotein (VLDL), high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, TG/HDL-C ratio and total cholesterol) was determined at rest, immediately after exercise and 1 h after exercise bouts. RESULTS: The time to exhaustion was lower in the low CHO condition compared with the control and high CHO condition (3.59 +/- 0.72; 2.91 +/- 0.56; and 4.26 +/- 0.69 min; P < 0.05). The energy expenditure (control: 251.1 +/- 56.0 kJ; low CHO: 215.2 +/- 28.6 kJ; and high CHO: 310.4 +/- 64.9 kJ) was significantly different between the low and high CHO conditions (P < 0.05). There were no significant changes in the lipid profile for any of the experimental conditions (control, low and high; P < 0.05). Glucose and insulin levels did not show time-dependent changes in any of the conditions (P > 0.05). CONCLUSIONS: These results indicate that a supramaximal exercise session has no significant effects on lipid metabolism.

Experimental chronic low-frequency resistance training produces skeletal muscle hypertrophy in the absence of muscle damage and metabolic stress markers.

Volitional animal resistance training constitutes an important approach to modeling human resistance training. However, the lack of standardization protocol poses a frequent impediment to the production of skeletal muscle hypertrophy and the study of related physiological variables (i.e., cellular damage/inflammation or metabolic stress). Therefore, the purposes of the present study were: (1) to test whether a long-term and low frequency experimental resistance training program is capable of producing absolute increases in muscle mass; (2) to examine whether cellular damage/inflammation or metabolic stress is involved in the process of hypertrophy. In order to test this hypothesis, animals were assigned to a sedentary control (C, n = 8) or a resistance trained group (RT, n = 7). Trained rats performed 2 exercise sessions per week (16 repetitions per day) during 12 weeks. Our results demonstrated that the resistance training strategy employed was capable of producing absolute mass gain in both soleus and plantaris muscles (12%, p < 0.05). Furthermore, muscle tumor necrosis factor (TNF-alpha) protein expression (soleus muscle) was reduced by 24% (p < 0.01) in trained group when compared to sedentary one. Finally, serum creatine kinase (CK) activity and serum lactate concentrations were not affected in either group. Such information may have practical applications if reproduced in situations where skeletal muscle hypertrophy is desired but high mechanical stimuli of skeletal muscle and inflammation are not.

Chronic low frequency/low volume resistance training reduces pro-inflammatory cytokine protein levels and TLR4 mRNA in rat skeletal muscle.

Skeletal muscle is the source of pro- and anti-inflammatory cytokines, and recently, it has been recognized as an important source of interleukin 6 (IL-6), a cytokine that exerts inhibitory effects on several pro-inflammatory cytokines. Although dynamic chronic resistance training has been shown to produce the known "repeated bout effect", which abolishes the acute muscle damage, performing of high-intensity resistance training has been regarded highly advisable, at least from the hypertrophy perspective. On the other hand, a more therapeutic, "non-damaging" resistance training program, mainly composed of concentric forces, low frequency/low volume of training, and the same exercise, could theoretically benefit the muscle when the main issue is to avoid muscle inflammation (as in the treatment of several "low-grade" inflammatory diseases) because the acute effect of each resistance exercise session could be diminished/avoided, at the same time that the muscle is still being overloaded in a concentric manner. However, the benefits of such "less demanding" resistance training schedule on the muscle inflammatory profile have never been investigated. Therefore, we assessed the protein expression of IL-6, TNF-alpha, IL-10, IL-10/TNF-alpha ratio, and HSP70 levels and mRNA expression of SCF(beta-TrCP), IL-15, and TLR-4 in the skeletal muscle of rats submitted to resistance training. Briefly, animals were randomly assigned to either a control group (S, n = 8) or a resistance-trained group (T, n = 7). Trained rats were exercised over a duration of 12 weeks (two times per day, two times per week). Detection of IL-6, TNF-alpha, IL-10, and HSP70 protein expression was carried out by western blotting and SCF(beta-TrCP) (SKP Cullin F-Box Protein Ligases), a class of enzymes involved in the ubiquitination of protein substrates to proteasomal degradation, IL-15, and TLR-4 by RT-PCR. Our results show a decreased expression of TNF-alpha and TLR4 mRNA (40 and 60%, respectively; p < 0.05) in the plantar muscle from trained, when compared with control rats. In conclusion, exercise training induced decreased TNF-alpha and TLR-4 expressions, resulting in a modified IL-10/TNF-alpha ratio in the skeletal muscle. These data show that, in healthy rats, 12-week resistance training, predominantly composed of concentric stimuli and low frequency/low volume schedule, down regulates skeletal muscle production of cytokines involved in the onset, maintenance, and regulation of inflammation.