RESUMEN
High-intensity unaccustomed eccentric contractions result in weakness and power loss because of fatigue and muscle damage. Through the repeated bout effect (RBE), adaptations occur, then damage and weakness are attenuated following a subsequent bout. However, it is unclear whether the RBE protects peak power output. We investigated the influence of the RBE on power production and estimated fatigue- and damage-induced neuromuscular impairments following repeated high-intensity eccentric contractions. Twelve healthy adult males performed 5 sets of 30 maximal eccentric elbow flexions and repeated an identical bout 4 weeks later. Recovery was tracked over 7 days following both bouts. Reduced maximum voluntary isometric contraction torque, and increased serum creatine kinase and self-reported soreness indirectly inferred muscle damage. Peak isotonic power, time-dependent measures - rate of velocity development (RVD) and rate of torque development (RTD) - and several electrophysiological indices of neuromuscular function were assessed. The RBE protected peak power, with a protective index of 66% 24 h after the second eccentric exercise bout. The protection of power also related to preserved RVD (R2 = 0.61, P < 0.01) and RTD (R2 = 0.39, P < 0.01). Furthermore, the RBE's protection against muscle damage permitted the estimation of fatigue-associated neuromuscular performance decrements following eccentric exercise. Novelty: The repeated bout effect protects peak isotonic power. Protection of peak power relates to preserved rates of torque and velocity development, but more so rate of velocity development. The repeated bout effect has little influence on indices of neuromuscular fatigue.
Asunto(s)
Adaptación Fisiológica , Contracción Muscular , Fatiga Muscular/fisiología , Músculo Esquelético/fisiología , Mialgia/fisiopatología , Adulto , Creatina Quinasa/sangre , Codo/fisiología , Humanos , Contracción Isométrica , Masculino , Músculo Esquelético/enzimología , Mialgia/enzimología , Autoinforme , Torque , Adulto JovenRESUMEN
We investigated the effect of postmatch cold-water immersion (CWI) on markers of muscle damage, neuromuscular fatigue, and perceptual responses within 72 h after a rugby match. Twenty-two professional male rugby players were randomized into CWI (10 °C/10 min; n = 11) or control (CON: 30 min seated; n = 11) groups. Activity profile from Global Positioning Satellite systems and postmatch rating of perceived exertion were measured to determined match load. Biochemical (tumor necrosis factor alpha (TNF-α), interleukin-6), neuromuscular performance (squat (SJ) and countermovement jumps (CMJ), peak power output (PPO), rate of force development (RFD), stiffness, 10- and 30-m sprint time, and perceptual markers (soreness, perceived recovery) were obtained before and immediately after the match, and then at 30 min, 24 h, 48 h, and 72 h after the match. Magnitude-based inference and Cohen's effect size (ES) were used to analyze change over time and between groups. Thus, the higher/beneficial, similar/trivial, or lower/harmful differences were evaluated as follows: <1%, almost certainly not; 1% to 5%, very unlikely; 5% to 25%, unlikely; 25% to 75%, possible; 75% to 95%, likely; 95% to 99%, very likely; >99%, almost certainly. Changes were unclear for the match loads, sprint times, and perceptual markers between groups. Higher %ΔSJ at 24 h (very likely (ES = 0.75)) and in %ΔPPO_SJ at 48 h (likely (ES = 0.51)) were observed in CWI than in CON. Values in %ΔRDF_CMJ were higher immediately after (likely (ES = 0.83)), 30 min after (very likely (ES = 0.97)), and 24 h after the match (likely (ES = 0.93)) in CWI than in CON. Furthermore, %Δlog TNF-α were lower in the CWI group than in the CON group immediately after (almost certainly (ES = -0.76)), 24 h after (very likely (ES = -1.09)), and 72 h after the match (likely (ES = -0.51)), and in Δstiffness_SJ at 30 min after (likely (ES = -0.67)) and 48 h after the match (very likely (ES = -0.97)). Also, different within-groups effects throughout postmatch were reported. Implementing postmatch CWI-based strategies improved the recovery of markers of inflammation and fatigue in rugby players, despite no change in markers of speed or perceptual recovery.
Asunto(s)
Atletas , Biomarcadores/análisis , Frío , Inmersión , Fatiga Muscular , Adulto , Rendimiento Atlético , Fútbol Americano , Humanos , Inflamación , Masculino , Adulto JovenRESUMEN
This study compared changes in brachial-ankle pulse wave velocity (baPWV) after concentric (CON) versus eccentric (ECC) cycling. It was hypothesized that baPWV would increase after the first ECC bout (ECC1) because of muscle damage, but not after the second ECC bout (ECC2), and would decrease after CON. Fifteen young (aged 20-30 years) men performed 2 bouts of 30-min ECC (ECC1 and ECC2) at 60% of maximal CON power output and 2 bouts of 30-min CON at the same intensity as that of ECC (CON1), and at the same oxygen consumption as that of ECC (CON2) every 2 weeks. Oxygen uptake during the cycling was recorded, and baPWV was measured before and at 0.5, 1, 24, and 48 h after each cycling bout. Maximal voluntary contraction (MVC) torque and muscle soreness of the knee extensors were assessed before and at 24 and 48 h after each cycling bout. Changes in these variables over time were compared among the 4 cycling bouts by 2-way repeated-measured ANOVA. baPWV decreased (P < 0.05) 8% from the baseline (1119 ± 116 cm/s) at 0.5 h after CON1 (1028 ± 126 cm/s), but no significant changes were evident after ECC1, ECC2, and CON2. MVC torque decreased 10% from the baseline at 24 h after ECC1, but no significant changes were evident after CON1, CON2, and ECC2. These results did not support the hypothesis, and suggest that minor muscle damage induced by eccentric cycling does not affect arterial stiffness.
Asunto(s)
Ciclismo/fisiología , Rigidez Vascular , Adulto , Índice Tobillo Braquial , Prueba de Esfuerzo , Humanos , Rodilla/fisiología , Masculino , Contracción Muscular , Músculo Esquelético/fisiología , Mialgia , Consumo de Oxígeno , Análisis de la Onda del Pulso , Torque , Adulto JovenRESUMEN
The purpose of this study was to investigate the effects of a single-dose of ß-hydroxy-ß-methylbutyrate free acid (HMB-FA) supplementation on muscle recovery after a high-intensity exercise bout. Twenty-three trained young males were randomly assigned to receive either a single-dose supplementation of 3 g of HMB-FA (n = 12; age, 22.8 ± 3.0 years) or placebo (PLA; n = 11; age, 22.9 ± 3.1 years). A muscle damage protocol was applied 60 min after supplementation, and consisted of 7 sets of 20 drop jumps from a 60-cm box with 2-min rest intervals between sets. Muscle swelling, countermovement jump (CMJ), maximal voluntary isometric torque (MVIT), and work capacity (WC) were measured before, immediately after, and 24, 48, and 72 h after the exercise protocol. Muscle swelling, CMJ, and MVIT changed similarly in both groups after the exercise protocol (p < 0.001), but returned to pre-exercise levels after 24 h in both groups. WC decreased similarly in both groups after the exercise protocol (p < 0.01). For HMB-FA, WC returned to pre-exercise level 24 h after exercise protocol. However, for PLA, WC did not return to pre-exercise level even 72 h after the exercise protocol. In summary, a single-dose of HMB-FA supplementation improved WC recovery after a high-intensity exercise bout. However, HMB-FA did not affect the time-course of muscle swelling, MVIT, and CMJ recovery.
Asunto(s)
Suplementos Dietéticos , Ejercicio Físico , Valeratos/administración & dosificación , Adolescente , Adulto , Relación Dosis-Respuesta a Droga , Método Doble Ciego , Humanos , Masculino , Recuerdo Mental , Músculo Esquelético/efectos de los fármacos , Enfermedades Musculares/prevención & control , Entrenamiento de Fuerza , Torque , Adulto JovenRESUMEN
The consumption of milk following eccentric exercise attenuates the effects of muscle damage in team-sport athletes. However, participation in team sport involves both concentric-eccentric loading and metabolic stress. Therefore, the aim of this study was to investigate the effects of postexercise milk consumption on recovery from a cycling protocol designed to simulate the metabolic demands of team sport. Ten female team-sport athletes participated in a randomised crossover investigation. Upon completion of the protocol participants consumed 500 mL of milk (MILK) or 500 mL of an energy-matched carbohydrate (CHO) drink. Muscle function (peak torque, rate of force development, countermovement jump, 20-m sprint), muscle soreness and tiredness, serum creatine kinase, high-sensitivity C-reactive protein, and measures of oxidative stress (protein carbonyls and reduced glutathione/oxidized glutathione (GSH/GSSG) ratio) were determined at pre-exercise and 24 h, 48 h, and 72 h postexercise. MILK had a possible beneficial effect in attenuating losses in peak torque (180°/s) from baseline to 24 h (3.2% ± 7.8% vs. -6.2% ± 7.5%, MILK vs. CHO) and a possible beneficial effect in minimising soreness (baseline-48 h; baseline-72 h) and tiredness (baseline-24 h; baseline-72 h). There was no change in oxidative stress following the exercise protocol, though a likely benefit of milk was observed for GSH/GSSG ratio at baseline-24 h (0.369 ×/÷ 1.89, 1.103 ×/÷ 3.96, MILK vs. CHO). MILK had an unclear effect on all other variables. Consumption of 500 mL of milk after repeat sprint cycling had little to no benefit in minimising losses in peak torque or minimising increases in soreness and tiredness and had no effect on serum markers of muscle damage and inflammation.
Asunto(s)
Rendimiento Atlético , Ciclismo , Leche , Músculo Esquelético/fisiología , Fenómenos Fisiológicos en la Nutrición Deportiva , Adulto , Animales , Atletas , Proteína C-Reactiva/metabolismo , Creatina Quinasa/sangre , Estudios Cruzados , Dieta , Ácido Edético/sangre , Ejercicio Físico , Femenino , Heparina/sangre , Humanos , Inflamación/sangre , Mialgia/prevención & control , Estrés Oxidativo , Estrés Fisiológico , Encuestas y Cuestionarios , Adulto JovenRESUMEN
The aim of this study was to compare the effects of beetroot juice (BTJ) and a nitrate only drink (sodium nitrate; SN) on indices of exercise-induced muscle damage (EIMD). Thirty recreationally active males consumed either BTJ (n = 10), a nitrate-matched SN drink (n = 10), or an isocaloric placebo (PLA; n = 10) immediately and at 24 and 48 h after performing 100 drop jumps. To assess muscle damage, maximal isometric voluntary contractions (MIVCs), countermovement jumps (CMJs), pressure-pain threshold (PPT), creatine kinase (CK), and high-sensitivity C-reactive protein (hs-CRP) were measured before, immediately after and at 24, 48, and 72 h following the drop jumps. BTJ and SN increased serum nitric oxide, which peaked at 2 h post-ingestion (136 ± 78 and 189 ± 79 µmol·L-1, respectively). PPT decreased in all groups postexercise (P = 0.001), but was attenuated with BTJ compared with SN and PLA (P = 0.043). PPT was 104% ± 26% of baseline values at 72 h after BTJ, 94% ± 16% after SN, and 91% ± 19% after PLA. MIVC and CMJ were reduced following exercise (-15% to 25%) and did not recover to baseline by 72 h in all groups; however, no group differences were observed (P > 0.05). Serum CK increased after exercise but no group differences were present (P > 0.05). hsCRP levels were unaltered by the exercise protocol (P > 0.05). These data suggest that BTJ supplementation is more effective than SN for attenuating muscle pain associated with EIMD, and that any analgesic effects are likely due to phytonutrients in BTJ other than nitrate, or interactions between them.
Asunto(s)
Beta vulgaris/química , Ejercicio Físico , Jugos de Frutas y Vegetales/análisis , Mialgia/prevención & control , Nitratos/administración & dosificación , Raíces de Plantas/química , Adulto , Proteína C-Reactiva/metabolismo , Creatina Quinasa/sangre , Dieta , Método Doble Ciego , Humanos , Masculino , Músculo Esquelético/efectos de los fármacos , Músculo Esquelético/fisiología , Nitratos/sangre , Adulto JovenRESUMEN
This study investigated the repeated bout effect of 3 typical lower body resistance-training sessions on maximal and submaximal effort running performance. Twelve resistance-untrained men (age, 24 ± 4 years; height, 1.81 ± 0.10 m; body mass, 79.3 ± 10.9 kg; peak oxygen uptake, 48.2 ± 6.5 mL·kg-1·min-1; 6-repetition maximum squat, 71.7 ± 12.2 kg) undertook 3 bouts of resistance-training sessions at 6-repetitions maximum. Countermovement jump (CMJ), lower-body range of motion (ROM), muscle soreness, and creatine kinase (CK) were examined prior to and immediately, 24 h (T24), and 48 h (T48) after each resistance-training bout. Submaximal (i.e., below anaerobic threshold (AT)) and maximal (i.e., above AT) running performances were also conducted at T24 and T48. Most indirect muscle damage markers (i.e., CMJ, ROM, and muscle soreness) and submaximal running performance were significantly improved (P < 0.05; 1.9%) following the third resistance-training bout compared with the second bout. Whilst maximal running performance was also improved following the third bout (P < 0.05; 9.8%) compared with other bouts, the measures were still reduced by 12%-20% versus baseline. However, the increase in CK was attenuated following the second bout (P < 0.05) with no further protection following the third bout (P > 0.05). In conclusion, the initial bout induced the greatest change in CK; however, at least 2 bouts were required to produce protective effects on other indirect muscle damage markers and submaximal running performance measures. This suggests that submaximal running sessions should be avoided for at least 48 h after resistance training until the third bout, although a greater recovery period may be required for maximal running sessions.
Asunto(s)
Rendimiento Atlético , Ejercicio Físico , Músculo Esquelético/fisiología , Carrera , Adulto , Biomarcadores/sangre , Creatina Quinasa/sangre , Tolerancia al Ejercicio , Humanos , Extremidad Inferior , Masculino , Músculo Esquelético/lesiones , Mialgia/etiología , Mialgia/prevención & control , Consumo de Oxígeno , Esfuerzo Físico , Rango del Movimiento Articular , Reproducibilidad de los Resultados , Carrera/lesiones , Factores de Tiempo , Adulto JovenRESUMEN
The cellular stress response of the rat tibialis anterior (TA) muscle was investigated following 20, 40, or 60 lengthening contractions (LCs) using an in vivo model of electrical stimulation. Muscles were removed at 0, 1, 3, or 24 h after LCs and assessed for heat shock transcription factor (HSF) activation, heat shock protein (HSP) content, and/or morphological evidence of muscle fibre damage. When compared with the first muscle contraction, peak muscle torque was reduced by 26% (p < 0.05) after 20 LCs and further reduced to 56% and 60% (p < 0.001) after 40 and 60 LCs, respectively. Following 60 LCs, HSF activation was detected at 0, 1, and 3 h but was undetectable at 24 h. Hsp72 content was elevated at 24 h after 20 LCs (2.34 ± 0.37 fold, p < 0.05), 40 LCs (3.02 ± 0.31 fold, p < 0.01), and 60 LCs (3.37 ± 0.21 fold, p < 0.001). Hsp25 content increased after 40 (2.36 ± 0.24 fold, p < 0.01) and 60 LCs (2.80 ± 0.37 fold, p < 0.01). Morphological assessment of TA morphology revealed that very few fibres were damaged following 20 LCs while multiple sets of LCs (40 and 60) caused greater amounts of fibre damage. Electron microscopy showed disrupted Z-lines and sarcomeres were detectable in some muscles fibres following 20 LCs but were more prevalent and severe in muscles subjected to 40 or 60 LCs. These results suggest LCs elevate HSP content by an HSF-mediated mechanism (60 LC) and a single set of 20 LCs is capable of increasing muscle HSP content without causing significant muscle fibre damage.
Asunto(s)
Contracción Muscular , Músculo Esquelético/fisiología , Estrés Fisiológico , Animales , Estimulación Eléctrica , Proteínas de Choque Térmico HSP27/metabolismo , Proteínas del Choque Térmico HSP72/metabolismo , Factores de Transcripción del Choque Térmico/metabolismo , Masculino , Fibras Musculares Esqueléticas/fisiología , Ratas , Ratas Sprague-DawleyRESUMEN
Unaccustomed eccentric contractions induce muscle damage, calcium homeostasis disruption, and mitochondrial alterations. Since exercise and hypoxia are known to modulate mitochondrial function, we aimed to analyze the effects on eccentric exercise-induced muscle damage (EEIMD) in trained rats using 2 recovery protocols based on: (i) intermittent hypobaric hypoxia (IHH) and (ii) IHH followed by exercise. The expression of biomarkers related to mitochondrial biogenesis, dynamics, oxidative stress, and bioenergetics was evaluated. Soleus muscles were excised before (CTRL) and 1, 3, 7, and 14 days after an EEIMD protocol. The following treatments were applied 1 day after the EEIMD: passive normobaric recovery (PNR), 4 h daily exposure to passive IHH at 4000 m (PHR) or IHH exposure followed by aerobic exercise (AHR). Citrate synthase activity was reduced at 7 and 14 days after application of the EEIMD protocol. However, this reduction was attenuated in AHR rats at day 14. PGC-1α and Sirt3 and TOM20 levels had decreased after 1 and 3 days, but the AHR group exhibited increased expression of these proteins, as well as of Tfam, by the end of the protocol. Mfn2 greatly reduced during the first 72 h, but returned to basal levels passively. At day 14, AHR rats had higher levels of Mfn2, OPA1, and Drp1 than PNR animals. Both groups exposed to IHH showed a lower p66shc(ser36)/p66shc ratio than PNR animals, as well as higher complex IV subunit I and ANT levels. These results suggest that IHH positively modulates key mitochondrial aspects after EEIMD, especially when combined with aerobic exercise.
Asunto(s)
Hipoxia/metabolismo , Mitocondrias/metabolismo , Condicionamiento Físico Animal , Animales , Apoptosis , Biomarcadores/metabolismo , Citrato (si)-Sintasa/metabolismo , Creatina Quinasa/sangre , Determinación de Punto Final , Metabolismo Energético , GTP Fosfohidrolasas , Regulación de la Expresión Génica , Masculino , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Proteínas de Transporte de Membrana , Proteínas del Complejo de Importación de Proteínas Precursoras Mitocondriales , Proteínas Mitocondriales/genética , Proteínas Mitocondriales/metabolismo , Músculo Esquelético/metabolismo , Mioglobina/sangre , Estrés Oxidativo , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/genética , Coactivador 1-alfa del Receptor Activado por Proliferadores de Peroxisomas gamma/metabolismo , Ratas , Ratas Sprague-Dawley , Receptores de Superficie Celular , Receptores Citoplasmáticos y Nucleares/genética , Receptores Citoplasmáticos y Nucleares/metabolismo , Sirtuinas/genética , Sirtuinas/metabolismo , Proteína Transformadora 1 que Contiene Dominios de Homología 2 de Src/genética , Proteína Transformadora 1 que Contiene Dominios de Homología 2 de Src/metabolismoRESUMEN
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% 1-repetition maximum to induce muscle damage. All participants were diet-controlled across the study. Creatine kinase, peak isometric knee-extensor force, perceived muscle soreness, and countermovement jump (CMJ) height were measured immediately before (baseline) and at 1 h, 24 h, and 48 h postexercise. 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 â¼87% vs. BCAA â¼92%; moderate, likely), CMJ at 24 h (placebo â¼93% vs. BCAA â¼96%; small, likely), and muscle soreness at both 24 h (placebo â¼685% vs. BCAA â¼531%; small, likely) and 48 h (placebo â¼468% vs. BCAA â¼350%; 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 with 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.
Asunto(s)
Aminoácidos de Cadena Ramificada/administración & dosificación , Atletas , Mialgia/prevención & control , Resistencia Física , Entrenamiento de Fuerza , Índice de Masa Corporal , Creatina Quinasa/metabolismo , Suplementos Dietéticos , Método Doble Ciego , Femenino , Humanos , Hipertrofia , Masculino , Fuerza Muscular , Mialgia/tratamiento farmacológico , Adulto JovenRESUMEN
We performed a placebo-controlled pre-clinical study to determine if sodium 4-phenylbutyrate (4PB) can reduce contraction-induced myofiber damage in the mdx mouse model of Duchenne muscular dystrophy (DMD). At 72 h post-eccentric contractions, 4PB significantly increased contractile torque and reduced myofiber damage and macrophage infiltration. We conclude that 4PB, which is approved by Health Canada (Pheburane) and the United States Food and Drug Administration (Buphenyl) for urea cycle disorders, might modify disease severity in patients with DMD.
Asunto(s)
Inhibidores de Histona Desacetilasas/uso terapéutico , Activación de Macrófagos/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Distrofia Muscular de Duchenne/tratamiento farmacológico , Manipulaciones Musculoesqueléticas/efectos adversos , Miofibrillas/efectos de los fármacos , Fenilbutiratos/uso terapéutico , Animales , Miembro Posterior , Inhibidores de Histona Desacetilasas/administración & dosificación , Inyecciones Intraperitoneales , Traumatismos de la Pierna/prevención & control , Masculino , Ratones Endogámicos mdx , Contracción Muscular/efectos de los fármacos , Músculo Esquelético/inmunología , Músculo Esquelético/lesiones , Músculo Esquelético/patología , Distrofia Muscular de Duchenne/inmunología , Distrofia Muscular de Duchenne/patología , Miofibrillas/inmunología , Miofibrillas/patología , Fenilbutiratos/administración & dosificación , TorqueRESUMEN
Myostatin dysfunction promotes muscle hypertrophy, which can complicate assessment of muscle properties. We examined force generating capacity and creatine kinase (CK) efflux from skeletal muscles of young mice before they reach adult body and muscle size. Isolated soleus (SOL) and extensor digitorum longus (EDL) muscles of Berlin high (BEH) mice with dysfunctional myostatin, i.e., homozygous for inactivating myostatin mutation, and with a wild-type myostatin (BEH+/+) were studied. The muscles of BEH mice showed faster (P < 0.01) twitch and tetanus contraction times compared with BEH+/+ mice, but only EDL displayed lower (P < 0.05) specific force. SOL and EDL of age-matched but not younger BEH mice showed greater exercise-induced CK efflux compared with BEH+/+ mice. In summary, myostatin dysfunction leads to impairment in muscle force generating capacity in EDL and increases susceptibility of SOL and EDL to protein loss after exercise.
Asunto(s)
Creatina Quinasa/metabolismo , Actividad Motora/fisiología , Contracción Muscular/fisiología , Músculo Esquelético/metabolismo , Miostatina/deficiencia , Animales , Femenino , RatonesRESUMEN
The study analyzed the effect of an açai (Euterpe oleracea Mart.) functional beverage (AB) on muscle and oxidative stress markers, cardiorespiratory responses, perceived exertion, and time-to-exhaustion during maximal treadmill running. The beverage was developed as an ergogenic aid for athletes and contained 27.6 mg of anthocyanins per dose. Fourteen athletes performed 3 exercise tests: a ramp-incremental maximal exercise test and 2 maximal exercise bouts performed in 2 conditions (AB and without AB (control)) at 90% maximal oxygen uptake. Blood was collected at baseline and after maximal exercise in both conditions to determine biomarkers. AB increased time to exhaustion during short-term high-intensity exercise (mean difference: 69 s, 95% confidence interval = -296 s to 159 s, t = 2.2, p = 0.045), attenuating the metabolic stress induced by exercise (p < 0.05). AB also reduced perceived exertion and enhanced cardiorespiratory responses (p < 0.05). The AB may be a useful and practical ergogenic aid to enhance performance during high-intensity training.
Asunto(s)
Bebidas , Euterpe , Músculo Esquelético/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Resistencia Física/efectos de los fármacos , Extractos Vegetales/farmacología , Adulto , Atletas , Humanos , Masculino , Músculo Esquelético/fisiopatología , Esfuerzo Físico/efectos de los fármacos , Carrera , Factores de TiempoRESUMEN
The cytoprotective proteins, Hsp25 and Hsp72, are increased in skeletal muscle after nondamaging, shortening contractions, but the temporal pattern of expression and stimulatory mechanisms remain unclear. Thus, we sought to define the in vivo temporal patterns of expression for Hsp25 and Hsp72 after 2 opposing contractions types. To do this, male Sprague-Dawley rats had 1 tibialis anterior (TA) muscle electrically stimulated (5 sets of 20 repetitions) while being either forcibly lengthened (LC) or shortened (SC). At 2, 8, 24, 48, 72, or 168 h after the contractions both the stimulated and the nonstimulated (contra-lateral control) TA muscles were removed and processed to examine muscle damage (hemotoxylin and eosin staining) and Hsp content (Western blot analyses). Cross-sections from TA muscles subjected to LCs showed muscle fibre damage at 8 h and thereafter. In contrast, no muscle fibre damage was observed at any time point following SCs. When normalized to contra-lateral controls, Hsp25 and Hsp72 content were significantly (P < 0.01) increased at 24 h (3.1- and 3.8-fold, respectively) and thereafter. There were no significant increases in Hsp25 or Hsp72 content at any time point following SC. These data suggest that LCs, but not SCs, result in Hsp accumulation and that the fibre/cellular damage sustained from LCs may be the stimulus for elevating Hsp content.
Asunto(s)
Proteínas de Choque Térmico HSP27/análisis , Proteínas del Choque Térmico HSP72/análisis , Contracción Muscular , Músculo Esquelético/química , Músculo Esquelético/fisiología , Animales , Masculino , Ratas , Ratas Sprague-DawleyRESUMEN
Tocopherols (commonly referred to as "vitamin E") are frequently studied antioxidants in exercise research. However, the studies are highly heterogeneous, which has resulted in contradicting opinions. The aim of this review is to identify similar studies investigating the effects of tocopherol supplementation on exercise performance and oxidative stress and to perform minimally biased qualitative comparisons and meta-analysis. The literature search and study selection were performed according to Cochrane guidelines. A 2-dimensional study execution process was developed to enable selection of similar and comparable studies. Twenty relevant studies were identified. The high variability of study designs resulted in final selection of 6 maximally relevant studies. Markers of lipid peroxidation (malondialdehyde) and muscle damage (creatine kinase) were the 2 most frequently and similarly measured variables. Meta comparison showed that tocopherol supplementation did not result in significant protection against either exercise-induced lipid peroxidation or muscle damage. The complex antioxidant nature of tocopherols and low accumulation rates in muscle tissues could underlie an absence of protective effects.