RESUMEN
The present study investigated whether acute capsaicin (CAP) supplementation improves mean power output (MPO) and peak velocity (PV) during the performance of the free bench press exercise (FBP). Twelve (n = 12) male Brazilian Jiu-Jitsu (BJJ) athletes (age: 24.3 ± 1.5 years, height: 1.74 ± 0.1 m, body mass: 75.7 ± 10.1 kg) participated in this randomized, placebo (PLA)-controlled, double-blind, crossover trial. For each condition, 45 min after CAP (12 mg purified) or PLA (12 mg of Celulomax E) consumption, the participants performed four sets of five repetitions of FBP at a load of 60% of body mass with five-min rest intervals. The MPO (t = 5.6, df = 11, p = 0.001, EF = 0.3, IC 95% = -0.55 to 1.05) and PV (t = 5.4, df = 11, p = 0.001, EF = 0.5, IC 95% = -0.32 to 1.30) were significantly higher with CAP supplementation versus PLA. Acute CAP supplementation appears to improve MPO and PV during FBP in male BJJ athletes.
RESUMEN
PURPOSE: To identify the effects of a single 30 min partial lower leg external pneumatic compression (EPC) treatment compared to a static compression (SC) garment or a no treatment control (CTL) on markers of recovery and performance following a muscle damaging protocol. METHODS: Thirty healthy, active males (23 ± 3 years; 180.2 ± 9.0 cm; 81.6 ± 11.3 kg) performed 100 drop jumps from a 0.6 m box followed by a randomized, single 30 min treatment of either a partial lower leg EPC device worn below the knee and above the ankle (110 mmHg), SC garment (20-30 mmHg) covering the foot and calf just below the knee, or no treatment CTL, and then returned 24 and 48 h later. Participants were assessed for measures of muscle soreness, fatigue, hemodynamics, blood lactate, muscle thickness, circumferences, and performance assessments. RESULTS: The drop jump protocol significantly increased muscle soreness (p < 0.001), fatigue (p < 0.001), blood flow (p < 0.001), hemoglobin (p < 0.001), and muscle oxygen saturation (SMO2; p < 0.001). Countermovement jump and squat jump testing completed after treatment with either EPC, SC, or CTL revealed no differences for jump height between any condition. However, EPC treatment maintained consistent braking force and propulsive power measures across all timepoints for countermovement jump testing. EPC and SC treatment also led to better maintenance of squat jump performance for average relative propulsive force and power variables at 24 and 48 h compared to CTL. CONCLUSIONS: A single 30 min partial leg EPC treatment may lead to more consistent jump performance following a damaging bout of exercise.
Asunto(s)
Rendimiento Atlético , Mialgia , Vestuario , Ejercicio Físico/fisiología , Fatiga , Humanos , Masculino , Músculo Esquelético/fisiologíaRESUMEN
BACKGROUND: We sought to determine the time course of changes in neuromuscular performance and muscle damage following a single rugby union match. METHODS: Fourteen male amateur rugby players (28.9 ± 3.5 yrs; 1.7 ± 5.1 m; 86.1 ± 11.1 kg) participated. Plasma activity of creatine kinase ([CK]) and lactate dehydrogenase (LDH), L-run test (change of direction) and 30-m sprint (T30; speed) with 10-m lap time (T10; acceleration) were assessed on six occasions: one week before the match (PRE) and immediately, 24, 48, 72, and 96 h post-match. RESULTS: Relative to PRE, LDH was elevated immediately post-match (+33.6% ± 13.6%; p < 0.001) and [CK] was elevated immediately (+64.1% ± 38.8%, p = 0.001) and 24 h post-match (+352% ± 317%; p = 0.024). L-run test time increased 16.0 ± 8.7% relative to PRE at 24 h post (p < 0.001) and remained elevated through 96 h post-match (p < 0.05). T10 and T30 times increased relative to PRE immediately post-match (+12.0% ± 10.4%, p = 0.008; and +6.1% ± 4.9%; p = 0.006, respectively), though T30 times were similar to baseline by 48 h post-match whereas T10 times remained elevated through 72 h post-match. CONCLUSIONS: A single, competitive rugby union match induces significant muscle damage and performance decrements with distinct time courses of recovery in amateur athletes. Notably, change of direction attributes (i.e., L-run) appear to have the longest time course to full recovery.
RESUMEN
PURPOSE: We investigated the effect of ischemic preconditioning (IPC) on performance of a 3 min maximal effort arm ergometer test in young women. METHODS: Twenty healthy women (23.1 (SD 3.3) years) performed a 3 min maximal effort arm cycling exercise, preceded by IPC on both arms or SHAM in a counterbalanced randomized crossover design. Both blood flow (via high resolution ultrasound; n = 17) and muscle oxygenation/deoxygenation (via near infrared spectroscopy; n = 5) were measured throughout the IPC/SHAM. Performance and perceptual/physiological (i.e., heart rate, blood lactate, rating of perceived exertion, and triceps brachialis oxygenation) parameters were recorded during the exercise test. RESULTS: Occlusion during IPC completely blocked brachial artery blood flow, decreased oxygenated hemoglobin/myoglobin (Δ[oxy(Hb + Mb)]), and increased deoxygenated Hb/Mb (Δ[deoxy(Hb + Mb)]). There were no differences (P > 0.797) in performance (peak, mean, and end power output) or in any perceptual/physiological variables during the 3 min all-out test between IPC/SHAM. During exercise, Δ[oxy(Hb + Mb)] initially decreased with no differences (P ≥ 0.296) between conditions and returned towards baseline by the completion of the test while Δ[deoxy(Hb + Mb)] increased with no differences between conditions and remained elevated until completion of the test (P ≥ 0.755). CONCLUSIONS: We verified the successful application of IPC via blood flow and NIRS measures but found no effects on performance of a 3 min maximal effort arm cranking test in young women.
Asunto(s)
Brazo , Prueba de Esfuerzo/métodos , Precondicionamiento Isquémico , Músculo Esquelético/fisiología , Consumo de Oxígeno/fisiología , Adulto , Ejercicio Físico , Femenino , Humanos , Adulto JovenRESUMEN
OBJECTIVE: We recently reported that curcumin supplementation in a metabolically (i.e., Western diet [WD]) and chemically (i.e., CCl4) induced female rat model of non-alcoholic steatohepatitis (NASH) was associated with lower liver pathology scores and molecular markers of inflammation. This occurred when curcumin was given during induction of disease (preventative arm; 8-week WD with or without curcumin [8WD + C vs. 8WD]) as well as when given after disease development (treatment arm; 12-week WD with or without curcumin during weeks 9-12 [12WD + C vs. 12WD]). Herein, we sought to extend our findings from that study by determining the effects of curcumin supplementation on cytokine/chemokine expression in serum collected from these same rats. RESULTS: 24 cytokines/chemokines were assayed. IL-2 (+ 80%) and IL-13 (+ 83%) were greater with curcumin supplementation in the prevention arm. IL-2 (+ 192%), IL-13 (+ 87%), IL-17A (+ 81%) and fractalkine (+ 121%) were higher while RANTES was lower (- 22%) with curcumin supplementation in the treatment arm (p < 0.05 for all). RANTES concentrations also correlated significantly with hepatic pathology scores of inflammation (r = 0.417, p = 0.008). Select serum cytokines/chemokines were affected with curcumin supplementation in this female rat model of NASH. Moreover, curcumin's effect(s) on RANTES and its association with liver disease pathogenesis and progression may warrant further investigation.
Asunto(s)
Antiinflamatorios/farmacología , Curcumina/farmacología , Suplementos Dietéticos , Regulación de la Expresión Génica/efectos de los fármacos , Hígado/efectos de los fármacos , Enfermedad del Hígado Graso no Alcohólico/dietoterapia , Animales , Tetracloruro de Carbono/administración & dosificación , Quimiocina CCL5/sangre , Quimiocina CCL5/genética , Quimiocina CX3CL1/sangre , Quimiocina CX3CL1/genética , Dieta Occidental/efectos adversos , Modelos Animales de Enfermedad , Esquema de Medicación , Femenino , Humanos , Interleucina-13/sangre , Interleucina-13/genética , Interleucina-17/sangre , Interleucina-17/genética , Interleucina-2/sangre , Interleucina-2/genética , Hígado/metabolismo , Hígado/patología , Enfermedad del Hígado Graso no Alcohólico/sangre , Enfermedad del Hígado Graso no Alcohólico/etiología , Enfermedad del Hígado Graso no Alcohólico/genética , Ratas , Ratas Wistar , Resultado del TratamientoRESUMEN
PURPOSE: Betalains are indole-derived pigments found in beet root, and recent studies suggest that they may exert ergogenic effects. Herein, we examined if supplementation for 7 days with betalain-rich beetroot concentrate (BLN) improved cycling performance or altered hemodynamic and serum analytes prior to, during and following a cycling time trial (TT). METHODS: Twenty-eight trained male cyclists (29 ± 10 years, 77.3 ± 13.3 kg, and 3.03 ± 0.62 W/kg) performed a counterbalanced crossover study whereby BLN (100 mg/day) or placebo (PLA) supplementation occurred over 7 days with a 1-week washout between conditions. On the morning of day seven of each supplementation condition, participants consumed one final serving of BLN or PLA and performed a 30-min cycling TT with concurrent assessment of several physiological variables and blood markers. RESULTS: BLN supplementation improved average absolute power compared to PLA (231.6 ± 36.2 vs. 225.3 ± 35.8 W, p = 0.050, d = 0.02). Average relative power, distance traveled, blood parameters (e.g., pH, lactate, glucose, NOx) and inflammatory markers (e.g., IL-6, IL-8, IL-10, TNFα) were not significantly different between conditions. BLN supplementation significantly improved exercise efficiency (W/ml/kg/min) in the last 5 min of the TT compared to PLA (p = 0.029, d = 0.45). Brachial artery blood flow in the BLN condition, immediately post-exercise, tended to be greater compared to PLA (p = 0.065, d = 0.32). CONCLUSIONS: We report that 7 days of BLN supplementation modestly improves 30-min TT power output, exercise efficiency as well as post-exercise blood flow without increasing plasma NOx levels or altering blood markers of inflammation, oxidative stress, and/or hematopoiesis.
Asunto(s)
Rendimiento Atlético/fisiología , Betalaínas/administración & dosificación , Ciclismo/fisiología , Suplementos Dietéticos , Consumo de Oxígeno/efectos de los fármacos , Sustancias para Mejorar el Rendimiento/administración & dosificación , Adulto , Estudios Cruzados , Método Doble Ciego , Humanos , Masculino , Adulto JovenRESUMEN
For the author R. Mac Thompson, the first name should be R. Mac and the last name should be Thompson. On SpringerLink the name is listed correctly, but on PubMed he is listed as Mac Thompson R.
RESUMEN
Curcumin, a naturally occurring plant polyphenolic compound, may have beneficial effects in nonalcoholic steatohepatitis (NASH) development. We examined whether curcumin supplementation could be used in both prevention and treatment of NASH with fibrosis. Female Wistar rats were provided ad libitum access to a "western diet" (WD) high in fat (43% kcal), sucrose (29% kcal), and cholesterol (2% w/v), as well as 15% fructose drinking water. Intraperitoneal CC14 injections (0.5 mL/kg) were also administered at weeks 1, 2, 4, and 6 to accelerate development of a NASH with fibrosis phenotype. Rats were randomized to four groups (n = 9-12/group) and fed ad libitum: (1) WD for 8-weeks (8WD), (2) WD enriched with curcumin for 8-weeks (8WD+C; 0.2% curcumin, BCM-95, DolCas Biotech) to assess prevention, (3) WD for 12-weeks (12WD), (4) WD for 8-weeks followed by 4-weeks WD+C (12WD+C) to assess treatment. Curcumin prevention (8WD vs. 8WD+C) attenuated (P < 0.05) histological liver inflammation, molecular markers of fibrosis (Col1a1 mRNA) and a serum marker of liver injury (AST). Curcumin treatment (12WD vs. 12WD+C) reduced (P < 0.05) hepatocellular inflammation, steatosis, NAFLD Activity Scores, and serum markers of liver injury (AST, ALP). Moreover, curcumin treatment also increased hepatic pACC/ACC, ApoB100, and SOD1 protein, and decreased hepatic FGF-21 levels; whereas, curcumin prevention increased hepatic glutathione levels. Both curcumin prevention and treatment reduced molecular markers of hepatic fibrosis (Col1a1 mRNA) and inflammation (TNF-α, SPP1 mRNA). Curcumin supplementation beneficially altered the NASH phenotype in female Wistar rats, particularly the reversal of hepatocellular inflammation.
Asunto(s)
Antiinflamatorios/uso terapéutico , Antioxidantes/uso terapéutico , Curcumina/uso terapéutico , Enfermedad del Hígado Graso no Alcohólico/tratamiento farmacológico , Animales , Antiinflamatorios/administración & dosificación , Apolipoproteína B-100/metabolismo , Colágeno/metabolismo , Curcumina/administración & dosificación , Dieta Alta en Grasa/efectos adversos , Femenino , Glutatión/metabolismo , Enfermedad del Hígado Graso no Alcohólico/etiología , Enfermedad del Hígado Graso no Alcohólico/prevención & control , Osteopontina/metabolismo , Ratas , Ratas Wistar , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
BACKGROUND: We sought to determine the effects of unilateral lower-limb external pneumatic compression (EPC) on bilateral lower-limb vascular reactivity and skin blood flow. METHODS: Thirty-two participants completed this two-aim study. In AIM1 (n = 18, age: 25.5 ± 4.7 years; BMI: 25.6 ± 3.5 kg/m2), bilateral femoral artery blood flow and reactivity (flow mediated dilation [FMD]) measurements were performed via ultrasonography at baseline (PRE) and immediately following 30-min of unilateral EPC treatment (POST). AIM2 (n = 14, age: 25.9 ± 4.5; BMI: 27.2 ± 2.7 kg/m2) involved 30-min unilateral EPC (n = 7) or sham (n = 7) treatment with thermographic bilateral lower-limb mean skin temperature (MST) measurements at baseline, 15-min of treatment (T15) and 0, 30 and 60-min (R0, R30, R60) following treatment. RESULTS: Comparative data herein are presented as mean ± 95% confidence interval. AIM1: No significant effects on total reactive hyperemia blood flow were observed for the treated (i.e., compressed) or untreated (i.e., non-compressed) leg. A significant effect of time, but no time*leg interaction, was observed for relative FMD indicating higher reactivity bilaterally with unilateral EPC treatment (FMD: +0.41 ± 0.09% across both legs; p < 0.05). AIM2: Unilateral EPC treatment was associated with significant increases in whole-leg MST from baseline during (T15: +0.63 ± 0.56 °C in the visible untreated/contralateral leg, p < 0.025) and immediately following treatment (i.e., R0) in both treated (+1.53 ± 0.59 °C) and untreated (+0.60 ± 0.45 °C) legs (p < 0.0125). Across both legs, MST remained elevated with EPC at 30-min post-treatment (+0.60 ± 0.45 °C; p < 0.0167) but not at 60-min post (+0.27 ± 0.46 °C; p = 0.165). Sham treatment was associated with a significant increase in the treated leg immediately post-treatment (+1.12 ± 0.31 °C; p < 0.0167), but not in the untreated leg (-0.27 ± 0.12 °C). MST in neither the treated or untreated leg were increased relative to baseline at R30 or R60 (p > 0.05). Finally, during treatment and at all post-treatment time points (i.e., R0, R30 and R60), independent of treatment group (EPC vs. sham), there was a significant effect of region. The maximum increase in MST was observed at the R0 time point and was significantly (p < 0.05) larger in the thigh region (+1.02 ± 0.31 °C) than the lower-leg (+0.47 ± 0.29 °C) region. However, similar rates of MST decline from R0 in the thigh and lower leg regions were observed at the R30 and R60 time points. DISCUSSION: Unilateral EPC may be an effective intervention for increasing skin blood flow and/or peripheral conduit vascular reactivity in the contralateral limb. While EPC was effective in increasing whole-leg MST bilaterally, there appeared to be a more robust response in the thigh compared to the lower-leg. Thus, proximity along the leg may be an important consideration in prospective treatment strategies.
RESUMEN
Adopting low carbohydrate, ketogenic diets remains a controversial issue for individuals who resistance train given that this form of dieting has been speculated to reduce skeletal muscle glycogen levels and stifle muscle anabolism. We sought to characterize the effects of a 12-week ketogenic diet (KD) on body composition, metabolic, and performance parameters in participants who trained recreationally at a local CrossFit facility. Twelve participants (nine males and three females, 31 ± 2 years of age, 80.3 ± 5.1 kg body mass, 22.9 ± 2.3% body fat, 1.37 back squat: body mass ratio) were divided into a control group (CTL; n = 5) and a KD group (n = 7). KD participants were given dietary guidelines to follow over 12 weeks while CTL participants were instructed to continue their normal diet throughout the study, and all participants continued their CrossFit training routine for 12 weeks. Pre, 2.5-week, and 12-week anaerobic performance tests were conducted, and pre- and 12-week tests were performed for body composition using dual X-ray absorptiometry (DXA) and ultrasound, resting energy expenditure (REE), blood-serum health markers, and aerobic capacity. Additionally, blood beta hydroxybutyrate (BHB) levels were measured weekly. Blood BHB levels were 2.8- to 9.5-fold higher in KD versus CTL throughout confirming a state of nutritional ketosis. DXA fat mass decreased by 12.4% in KD (p = 0.053). DXA total lean body mass changes were not different between groups, although DXA dual-leg lean mass decreased in the KD group by 1.4% (p = 0.068), and vastus lateralis thickness values decreased in the KD group by ~8% (p = 0.065). Changes in fasting glucose, HDL cholesterol, and triglycerides were similar between groups, although LDL cholesterol increased ~35% in KD (p = 0.048). Between-group changes in REE, one-repetition maximum (1-RM) back squat, 400 m run times, and VO2peak were similar between groups. While our n-sizes were limited, these preliminary data suggest that adopting a ketogenic diet causes marked reductions in whole-body adiposity while not impacting performance measures in recreationally-trained CrossFit trainees. Whether decrements in dual-leg muscle mass and vastus lateralis thickness in KD participants were due to fluid shifts remain unresolved, and increased LDL-C in these individuals warrants further investigation.
RESUMEN
Endurance (END)- and resistance (RES)-trained males performed interval running or resistance exercise during three consecutive days (bouts 1-3). Muscle biopsies were obtained at baseline, 2 h post-bout 1, and 72 h post-bout 3. Amino acid transporter SNAT2 mRNA was 75% greater in END (group p = 0.008), and increased ~ 70% 2 h post in both groups (time p = 0.023). Amino acid transporter PAT1 mRNA was 2.7-fold greater in RES (group p = 0.002). Baseline protein levels of the mitochondrial aminotransferase BCAT2 were 79% greater in END (p = 0.015).
Asunto(s)
Antígenos de Histocompatibilidad Menor/biosíntesis , Músculo Esquelético/metabolismo , Resistencia Física/fisiología , Proteínas Gestacionales/biosíntesis , Entrenamiento de Fuerza , Carrera/fisiología , Transaminasas/biosíntesis , Adulto , Humanos , Masculino , Factores de TiempoRESUMEN
We sought to determine whether age-related gastrocnemius muscle mass loss was associated with parallel decrements in androgen receptor (AR) or select Wnt signaling markers. To test this hypothesis, serum-free and total testosterone (TEST) and gastrocnemius AR and Wnt signaling markers were analyzed in male Fischer 344 rats that were 3, 6, 12, 18, and 24 mo (mo) old ( n = 9 per group). Free and total TEST was greatest in 6 mo rats, and AR protein and Wnt5 protein levels linearly declined with aging. There were associations between Wnt5 protein levels and relative gastrocnemius mass ( r = 0.395, P = 0.007) as well as AR and Wnt5 protein levels (r = 0.670, P < 0.001). We next tested the hypothesis that Wnt5 affects muscle fiber size by treating C2C12-derived myotubes with lower (75 ng/ml) and higher (150 ng/ml) concentrations of recombinant Wnt5a protein. Both treatments increased myotube size ( P < 0.05) suggesting this ligand may affect muscle fiber size in vivo. We next tested if Wnt5a protein levels were androgen-modulated by examining 10-mo-old male Fischer 344 rats ( n = 10-11 per group) that were orchiectomized and treated with testosterone-enanthate (TEST-E); trenbolone enanthate (TREN), a nonaromatizable synthetic testosterone analogue; or a vehicle (ORX only) for 4 wk. Interestingly, TEST-E and TREN treatments increased Wnt5a protein in the androgen-sensitive levator ani/bulbocavernosus muscle compared with ORX only ( P < 0.05). To summarize, aromatizable and nonaromatizable androgens increase Wnt5a protein expression in skeletal muscle, age-related decrements in muscle AR may contribute Wnt5a protein decrements, and our in vitro data imply this mechanism may contribute to age-related muscle loss. NEW & NOTEWORTHY Results from this study demonstrate androgen and Wnt5 protein expression decrease with aging, and this may be a mechanism involved with age-related muscle loss.
Asunto(s)
Andrógenos/metabolismo , Atrofia/metabolismo , Músculo Esquelético/metabolismo , Vía de Señalización Wnt/fisiología , Animales , Masculino , Fibras Musculares Esqueléticas/metabolismo , Orquiectomía/métodos , Tamaño de los Órganos/fisiología , Ratas , Ratas Endogámicas F344 , Receptores Androgénicos/metabolismo , Testosterona/análogos & derivados , Testosterona/metabolismo , Acetato de Trembolona/metabolismo , Proteína Wnt-5a/metabolismoRESUMEN
We sought to identify biomarkers which delineated individual hypertrophic responses to resistance training. Untrained, college-aged males engaged in full-body resistance training (3 d/wk) for 12 weeks. Body composition via dual x-ray absorptiometry (DXA), vastus lateralis (VL) thickness via ultrasound, blood, VL muscle biopsies, and three-repetition maximum (3-RM) squat strength were obtained prior to (PRE) and following (POST) 12 weeks of training. K-means cluster analysis based on VL thickness changes identified LOW [n = 17; change (mean±SD) = +0.11±0.14 cm], modest (MOD; n = 29, +0.40±0.06 cm), and high (HI; n = 21, +0.69±0.14 cm) responders. Biomarkers related to histology, ribosome biogenesis, proteolysis, inflammation, and androgen signaling were analyzed between clusters. There were main effects of time (POST>PRE, p<0.05) but no cluster×time interactions for increases in DXA lean body mass, type I and II muscle fiber cross sectional area and myonuclear number, satellite cell number, and macronutrients consumed. Interestingly, PRE VL thickness was ~12% greater in LOW versus HI (p = 0.021), despite POST values being ~12% greater in HI versus LOW (p = 0.006). However there was only a weak correlation between PRE VL thickness scores and change in VL thickness (r2 = 0.114, p = 0.005). Forced post hoc analysis indicated that muscle total RNA levels (i.e., ribosome density) did not significantly increase in the LOW cluster (351±70 ng/mg to 380±62, p = 0.253), but increased in the MOD (369±115 to 429±92, p = 0.009) and HI clusters (356±77 to 470±134, p<0.001; POST HI>POST LOW, p = 0.013). Nonetheless, there was only a weak association between change in muscle total RNA and VL thickness (r2 = 0.079, p = 0.026). IL-1ß mRNA levels decreased in the MOD and HI clusters following training (p<0.05), although associations between this marker and VL thickness changes were not significant (r2 = 0.0002, p = 0.919). In conclusion, individuals with lower pre-training VL thickness values and greater increases muscle total RNA levels following 12 weeks of resistance training experienced greater VL muscle growth, although these biomarkers individually explained only ~8-11% of the variance in hypertrophy.
Asunto(s)
Biomarcadores , Ejercicio Físico , Músculo Esquelético/anatomía & histología , Músculo Esquelético/fisiología , Entrenamiento de Fuerza , Adulto , Andrógenos/metabolismo , Composición Corporal , Análisis por Conglomerados , Expresión Génica , Humanos , Hipertrofia , Micronutrientes , Fibras Musculares Esqueléticas/citología , Fibras Musculares Esqueléticas/fisiología , Fuerza Muscular , Músculo Esquelético/diagnóstico por imagen , Ribosomas , Células Satélite del Músculo Esquelético/citología , Células Satélite del Músculo Esquelético/fisiología , Autoinforme , Transducción de Señal , Ultrasonografía , Adulto JovenRESUMEN
Previous investigations have reported a relationship between skeletal muscle phenotype and motor unit (MU) firing parameters during submaximal contractions. The purpose of the current investigation, however, was to examine the relationships between motor unit firing behavior during a maximal voluntary contraction, Myosin Heavy Chain (MHC) isoform content, and various molecular neuromuscular targets of the vastus lateralis (VL) muscle in resistance-trained men. Ten resistance-trained males completed a trapezoidal ramp contraction up to 100% of their maximal voluntary isometric strength (MVIC). Surface electromyography was recorded from the VL using a multichannel electrode array and decomposed to examine the firing characteristics of individual MUs. A skeletal muscle biopsy of the VL was also collected from each subject. Regression analyses were performed to identify relationships between type II fiber area and the slopes and/or intercepts of the mean firing rate (FRMEAN ) versus recruitment threshold (RT), max firing rate (FRMAX ) versus RT, and RT versus MU action potential amplitude (MUAPPP ) relationships. There were significant inverse relationships between type II fiber area and the y-intercept of the FR versus RT relationship (P < 0.05). Additionally, strong relationships (r > 0.5) were found between type II fiber area and FRMEAN versus RT slope and RT versus MUAPPP slope and intercept. These data further support the hypothesis that skeletal muscle phenotype is related to MU behavior during isometric contraction. However, our data, in concert with previous investigations, may suggest that these relationships are influenced by the intensity of the contraction.
Asunto(s)
Contracción Isométrica , Músculo Esquelético/fisiología , Reclutamiento Neurofisiológico , Potenciales Evocados Motores , Humanos , Masculino , Músculo Esquelético/metabolismo , Cadenas Pesadas de Miosina/metabolismo , Fenotipo , Adulto JovenRESUMEN
BACKGROUND: We sought to determine the effect of multiple walking breaks from sedentary behavior (SED) on glucose responses in sedentary obese women. MATERIALS AND METHODS: Ten women [aged = 36 (5) y, body mass index = 38.0 (1.6) kg/m2, body fat = 49.6 (1.4)%] completed 3 conditions (48-h "washout" in-between conditions) following a standardized meal in random order: 4-hour SED, 4-hour SED with 2 minutes of moderate-intensity walking every 30 minutes (SED + 2 min), and 4-hour SED with 5 minutes of moderate-intensity walking every 30 minutes (SED + 5 min). Measurements included continuous interstitial glucose concentration monitoring immediately before and during standardized conditions and accelerometry for physical activity patterns during and in-between the standardized conditions. Repeated-measures 1-way analyses of variance (α = .05) with Bonferroni correction for post hoc comparisons were performed. Effect sizes (d [95% confidence interval]) were calculated as mean difference from SED/pooled standard deviation. RESULTS: Sedentary time was similar in the 48 hours preceding each condition (P > .05). By design, sedentary time was different between conditions (P < .001). Compared with SED, 2-hour postprandial glucose positive incremental area under the curve was lower for SED + 5 minutes (P = .005; d = - 0.57 [-1.48, 0.40]), but not for SED + 2 minutes (P = .086; d = - 0.71 [-1.63, 0.27]). Four-hour postprandial glucose area under the curve was similar between conditions (P > .05). CONCLUSION: In sedentary obese women, 5 minutes of moderate-intensity walking breaks from SED each 30 minutes attenuate 2-hour postprandial glucose excursions.
Asunto(s)
Glucemia/metabolismo , Ejercicio Físico/fisiología , Obesidad/terapia , Caminata/fisiología , Adulto , Femenino , Humanos , Conducta SedentariaRESUMEN
Herein, we examined if acute or chronic resistance exercise affected markers of skeletal muscle long interspersed nuclear element-1 (LINE-1) retrotransposon activity. In study 1, 10 resistance-trained college-aged men performed three consecutive daily back squat sessions, and vastus lateralis biopsies were taken before (Pre), 2 h following session 1 (Post1), and 3 days following session 3 (Post2). In study 2, 13 untrained college-aged men performed a full-body resistance training program (3 days/wk), and vastus lateralis biopsies were taken before ( week 0) and ~72 h following training cessation ( week 12). In study 1, LINE-1 mRNA decreased 42-48% at Post1 and 2 ( P < 0.05), and reverse transcriptase (RT) activity trended downward at Post2 (-37%, P = 0.067). In study 2, LINE-1 mRNA trended downward at week 12 (-17%, P = 0.056) while LINE-1 promoter methylation increased (+142%, P = 0.041). Open reading frame (ORF)2p protein expression (-24%, P = 0.059) and RT activity (-26%, P = 0.063) also trended downward by week 12. Additionally, changes in RT activity versus satellite cell number were inversely associated ( r = -0.725, P = 0.008). Follow-up in vitro experiments demonstrated that 48-h treatments with lower doses (1 µM and 10 µM) of efavirenz and nevirapine (non-nucleoside RT inhibitors) increased myoblast proliferation ( P < 0.05). However, we observed a paradoxical decrease in myoblast proliferation with higher doses (50 µM) of efavirenz and delavirdine. This is the first report suggesting that resistance exercise downregulates markers of skeletal muscle LINE-1 activity. Given our discordant in vitro findings, future research is needed to thoroughly assess whether LINE-1-mediated RT activity enhances or blunts myoblast, or primary satellite cell, proliferative capacity.
Asunto(s)
Proliferación Celular , Elementos de Nucleótido Esparcido Largo , Contracción Muscular , Músculo Cuádriceps/metabolismo , ARN Mensajero/metabolismo , Entrenamiento de Fuerza/métodos , Células Satélite del Músculo Esquelético/metabolismo , Animales , Línea Celular , Proliferación Celular/efectos de los fármacos , Regulación hacia Abajo , Endonucleasas/genética , Endonucleasas/metabolismo , Humanos , Masculino , Ratones , Músculo Cuádriceps/efectos de los fármacos , ARN Mensajero/genética , ADN Polimerasa Dirigida por ARN/genética , ADN Polimerasa Dirigida por ARN/metabolismo , Inhibidores de la Transcriptasa Inversa/farmacología , Células Satélite del Músculo Esquelético/efectos de los fármacos , Factores de Tiempo , Adulto JovenRESUMEN
Recent evidence suggests that resistance training with light or heavy loads to failure results in similar adaptations. Herein, we compared how both training modalities affect the molecular, neuromuscular, and recovery responses following exercise. Resistance-trained males (mean ± SE: 22 ± 2 years, 84.8 ± 9.0 kg, 1.79 ± 0.06 m; n = 15) performed a crossover design of four sets of leg extensor exercise at 30% (light RE) or 80% (heavy RE) one repetition maximum (1RM) to repetition failure, and heavy RE or light RE 1 week later. Surface electromyography (EMG) was monitored during exercise, and vastus lateralis muscle biopsies were collected at baseline (PRE), 15 min (15mPOST), and 90 min following RE (90mPOST) for examination of molecular targets and fiber typing. Isokinetic dynamometry was also performed before (PRE), immediately after (POST), and 48 h after (48hPOST) exercise. Dependent variables were analyzed using repeated measures ANOVAs and significance was set at P ≤ 0.05. Repetitions completed were greater during light RE (P < 0.01), while EMG amplitude was greater during heavy RE (P ≤ 0.01). POST isokinetic torque was reduced following light versus heavy RE (P < 0.05). Postexercise expression of mRNAs and phosphoproteins associated with muscle hypertrophy were similar between load conditions. Additionally, p70s6k (Thr389) phosphorylation and fast-twitch fiber proportion exhibited a strong relationship after both light and heavy RE (r > 0.5). While similar mRNA and phosphoprotein responses to both modalities occurred, we posit that heavy RE is a more time-efficient training method given the differences in total repetitions completed, lower EMG amplitude during light RE, and impaired recovery response after light RE.
Asunto(s)
Músculo Cuádriceps/fisiología , Entrenamiento de Fuerza/métodos , Humanos , Masculino , Contracción Muscular , Músculo Cuádriceps/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Entrenamiento de Fuerza/efectos adversos , Proteínas Quinasas S6 Ribosómicas 70-kDa/genética , Proteínas Quinasas S6 Ribosómicas 70-kDa/metabolismo , Adulto JovenRESUMEN
PURPOSE: To compare the effects of external pneumatic compression (EPC) and sham when used concurrently with high intensity interval training (HIIT) on performance-related outcomes and recovery-related molecular measures. METHODS: Eighteen recreationally endurance-trained male participants (age: 21.6 ± 2.4 years, BMI: 25.7 ± 0.5 kg/m2, VO2peak: 51.3 ± 0.9 mL/kg/min) were randomized to balanced sham and EPC treatment groups. Three consecutive days of HIIT followed by EPC/sham treatment (Days 2-4) and 3 consecutive days of recovery (Days 5-7) with EPC/sham only on Days 5-6 were employed. Venipuncture, flexibility and pressure-to-pain threshold (PPT) measurements were made throughout. Vastus lateralis muscle was biopsied at PRE (i.e., Day 1), 1-h post-EPC/sham treatment on Day 2 (POST1), and 24-h post-EPC/sham treatment on Day 7 (POST2). 6-km run time trial performance was tested at PRE and POST2. RESULTS: No group × time interaction was observed for flexibility, PPT, or serum measures of creatine kinase (CK), hsCRP, and 8-isoprostane. However, there was a main effect of time for serum CK (p = 0.005). Change from PRE in 6-km run times at POST2 were not significantly different between groups. Significant between-groups differences existed for change from PRE in atrogin-1 mRNA (p = 0.018) at the POST1 time point (EPC: - 19.7 ± 8.1%, sham: + 7.7 ± 5.9%) and atrogin-1 protein concentration (p = 0.013) at the POST2 time point (EPC: - 31.8 ± 7.5%, sham: + 96.0 ± 34.7%). In addition, change from PRE in poly-Ub proteins was significantly different between groups at both the POST1 (EPC: - 26.0 ± 10.3%, sham: + 34.8 ± 28.5%; p = 0.046) and POST2 (EPC: - 33.7 ± 17.2%, sham: + 21.4 ± 14.9%; p = 0.037) time points. CONCLUSIONS: EPC when used concurrently with HIIT and in subsequent recovery days reduces skeletal muscle markers of proteolysis.
Asunto(s)
Entrenamiento de Intervalos de Alta Intensidad/métodos , Aparatos de Compresión Neumática Intermitente/efectos adversos , Proteolisis , Adulto , Proteína C-Reactiva/metabolismo , Creatina Quinasa/sangre , Dinoprost/análogos & derivados , Dinoprost/sangre , Entrenamiento de Intervalos de Alta Intensidad/efectos adversos , Humanos , Masculino , Proteínas Musculares/metabolismo , Músculo Cuádriceps/irrigación sanguínea , Músculo Cuádriceps/metabolismo , Músculo Cuádriceps/fisiología , Proteínas Ligasas SKP Cullina F-box/metabolismo , UbiquitinaciónRESUMEN
BACKGROUND: We sought to determine if a pre-workout supplement (PWS), containing multiple ingredients thought to enhance blood flow, increases hyperemia associated with resistance training compared to placebo (PBO). Given the potential interaction with training loads/time-under-tension, we evaluated the hyperemic response at two different loads to failure. METHODS: Thirty males participated in this double-blinded study. At visit 1, participants were randomly assigned to consume PWS (Reckless™) or PBO (maltodextrin and glycine) and performed four sets of leg extensions to failure at 30% or 80% of their 1-RM 45-min thereafter. 1-wk. later (visit 2), participants consumed the same supplement as before, but exercised at the alternate load. Heart rate (HR), blood pressure (BP), femoral artery blood flow, and plasma nitrate/nitrite (NOx) were assessed at baseline (BL), 45-min post-PWS/PBO consumption (PRE), and 5-min following the last set of leg extensions (POST). Vastus lateralis near infrared spectroscopy (NIRS) was employed during leg extension exercise. Repeated measures ANOVAs were performed with time, supplement, and load as independent variables and Bonferroni correction applied for multiple post-hoc comparisons. Data are reported as mean ± SD. RESULTS: With the 30% training load compared to 80%, significantly more repetitions were performed (p < 0.05), but there was no difference in total volume load (p > 0.05). NIRS derived minimum oxygenated hemoglobin (O2Hb) was lower in the 80% load condition compared to 30% for all rest intervals between sets of exercise (p < 0.0167). HR and BP did not vary as a function of supplement or load. Femoral artery blood flow at POST was higher independent of exercise load and treatment. However, a time*supplement*load interaction was observed revealing greater femoral artery blood flow with PWS compared to PBO at POST in the 80% (+56.8%; p = 0.006) but not 30% load condition (+12.7%; p = 0.476). Plasma NOx was ~3-fold higher with PWS compared to PBO at PRE and POST (p < 0.001). CONCLUSIONS: Compared to PBO, the PWS consumed herein augmented hyperemia following multiple sets to failure at 80% of 1-RM, but not 30%. This specificity may be a product of interaction with local perturbations (e.g., reduced tissue oxygenation levels [minimum O2Hb] in the 80% load condition) and/or muscle fiber recruitment.