Vicia faba Peptide Network Supplementation Does Not Differ From Milk Protein in Modulating Changes in Muscle Size During Short-Term Immobilization and Subsequent Remobilization, but Increases Muscle Protein Synthesis Rates During Remobilization in Healthy Young Men.

BACKGROUND: Muscle mass and strength decrease during short periods of immobilization and slowly recover during remobilization. Recent artificial intelligence applications have identified peptides that appear to possess anabolic properties in in vitro assays and murine models. OBJECTIVES: This study aimed to compare the impact of Vicia faba peptide network compared with milk protein supplementation on muscle mass and strength loss during limb immobilization and regain during remobilization. METHODS: Thirty young (24 ± 5 y) men were subjected to 7 d of one-legged knee immobilization followed by 14 d of ambulant recovery. Participants were randomly allocated to ingest either 10 g of the Vicia faba peptide network (NPN_1; n = 15) or an isonitrogenous control (milk protein concentrate; MPC; n = 15) twice daily throughout the study. Single-slice computed tomography scans were performed to assess quadriceps cross-sectional area (CSA). Deuterium oxide ingestion and muscle biopsy sampling were applied to measure myofibrillar protein synthesis rates. RESULTS: Leg immobilization decreased quadriceps CSA (primary outcome) from 81.9 ± 10.6 to 76.5 ± 9.2 cm2 and from 74.8 ± 10.6 to 71.5 ± 9.8 cm2 in the NPN_1 and MPC groups, respectively (P < 0.001). Remobilization partially recovered quadriceps CSA (77.3 ± 9.3 and 72.6 ± 10.0 cm2, respectively; P = 0.009), with no differences between the groups (P > 0.05). During immobilization, myofibrillar protein synthesis rates (secondary outcome) were lower in the immobilized leg (1.07% ± 0.24% and 1.10% ± 0.24%/d, respectively) than in the non-immobilized leg (1.55% ± 0.27% and 1.52% ± 0.20%/d, respectively; P < 0.001), with no differences between the groups (P > 0.05). During remobilization, myofibrillar protein synthesis rates in the immobilized leg were greater with NPN_1 than those with MPC (1.53% ± 0.38% vs. 1.23% ± 0.36%/d, respectively; P = 0.027). CONCLUSION: NPN_1 supplementation does not differ from milk protein in modulating the loss of muscle size during short-term immobilization and the regain during remobilization in young men. NPN_1 supplementation does not differ from milk protein supplementation in modulating the myofibrillar protein synthesis rates during immobilization but further increases myofibrillar protein synthesis rates during remobilization.

Five Days of Tart Cherry Supplementation Improves Exercise Performance in Normobaric Hypoxia.

Previous studies have shown tart cherry (TC) to improve exercise performance in normoxia. The effect of TC on hypoxic exercise performance is unknown. This study investigated the effects of 5 days of tart cherry (TC) or placebo (PL) supplementation on hypoxic exercise performance. Thirteen healthy participants completed an incremental cycle exercise test to exhaustion (TTE) under two conditions: (i) hypoxia (13% O2) with PL and (ii) hypoxia with TC (200 mg anthocyanin per day for 4 days and 100 mg on day 5). Pulmonary gas exchange variables, peripheral arterial oxygen saturation (SpO2), deoxygenated hemoglobin (HHb), and tissue oxygen saturation (StO2) assessed by near-infrared spectroscopy in the vastus lateralis muscle were measured at rest and during exercise. Urinary 8-hydro-2' deoxyguanosine (8-OHdG) excretion was evaluated pre-exercise and 1 and 5 h post-exercise. The TTE after TC (940 ± 84 s, mean ± standard deviation) was longer than after PL (912 ± 63 s, p < 0.05). During submaximal hypoxic exercise, HHb was lower and StO2 and SpO2 were higher after TC than PL. Moreover, a significant interaction (supplements × time) in urinary 8-OHdG excretion was found (p < 0.05), whereby 1 h post-exercise increases in urinary 8-OHdG excretion tended to be attenuated after TC. These findings indicate that short-term dietary TC supplementation improved hypoxic exercise tolerance, perhaps due to lower HHb and higher StO2 in the working muscles during submaximal exercise.

Neuromuscular electrical stimulation effect on mRNA expression of skeletal muscle in elderly.

Considering the increasing number of elderly in the world, this research aimed to investigate the effect of neuromuscular electrical stimulation (NMES) on changes in muscle mRNA abundance of a number of gene targets for improving the balance of the elderly. Twenty-six elderly undertook 30 minutes of quadriceps NMES (50 Hz, current at the limit of tolerance). Vastus lateralis muscle biopsies were obtained at rest immediately before and 24 hours after the intervention. The expression of 384 targeted mRNA transcripts was assessed by Real-time TaqMan PCR. A significant change in expression from baseline was determined using the ΔΔCT method with a false discovery rate (FDR) of <5%. The results showed that the biological functions of upregulated genes included muscle protein turnover, hypertrophy, inflammation, and muscle growth, while downregulated genes included mitochondrial and cell signaling functions. In general conclusion, it can be said that NMES can improve balance in the elderly. Therefore, considering the importance of balance in old people, it is suggested to use this method to improve the balance of the elderly.

Shatavari Supplementation in Postmenopausal Women Improves Handgrip Strength and Increases Vastus lateralis Myosin Regulatory Light Chain Phosphorylation but Does Not Alter Markers of Bone Turnover.

Shatavari has long been used as an Ayurvedic herb for women's health, but empirical evidence for its effectiveness has been lacking. Shatavari contains phytoestrogenic compounds that bind to the estradiol receptor. Postmenopausal estradiol deficiency contributes to sarcopenia and osteoporosis. In a randomised double-blind trial, 20 postmenopausal women (68.5 ± 6 years) ingested either placebo (N = 10) or shatavari (N = 10; 1000 mg/d, equivalent to 26,500 mg/d fresh weight shatavari) for 6 weeks. Handgrip and knee extensor strength were measured at baseline and at 6 weeks. Vastus lateralis (VL) biopsy samples were obtained. Data are presented as difference scores (Week 6-baseline, median ± interquartile range). Handgrip (but not knee extensor) strength was improved by shatavari supplementation (shatavari +0.7 ± 1.1 kg, placebo -0.4 ± 1.3 kg; p = 0.04). Myosin regulatory light chain phosphorylation, a known marker of improved myosin contractile function, was increased in VL following shatavari supplementation (immunoblotting; placebo -0.08 ± 0.5 a.u., shatavari +0.3 ± 1 arbitrary units (a.u.); p = 0.03). Shatavari increased the phosphorylation of Aktser473 (Aktser473 (placebo -0.6 ± 0.6 a.u., shatavari +0.2 ± 1.3 a.u.; p = 0.03) in VL. Shatavari supplementation did not alter plasma markers of bone turnover (P1NP, ß-CTX) and stimulation of human osteoblasts with pooled sera (N = 8 per condition) from placebo and shatavari supplementation conditions did not alter cytokine or metabolic markers of osteoblast activity. Shatavari may improve muscle function and contractility via myosin conformational change and further investigation of its utility in conserving and enhancing musculoskeletal function, in larger and more diverse cohorts, is warranted.

Effect of exercise intensity on metabolic responses on combined application of electrical stimulation and voluntary exercise.

The combined application of voluntary exercises and neuromuscular electrical stimulation (NMES) has been developed as a new type of exercise that can recruit motor units contributing to both aerobic and anaerobic energy metabolisms. We aimed to investigate the effect of voluntary exercise intensity on metabolic responses on the combination of voluntary exercise and NMES. In 13 volunteers, oxygen consumption and the blood lactate concentration were measured during (1) voluntary pedaling exercise at four different intensities: 50%, 75%, 100%, and 125% of the ventilatory threshold (VT) (VOL), (2) these voluntary exercises with superimposed NMES applied to the gluteus and thigh muscles (VOL+NMES), and (3) NMES only (NMES). Oxygen consumption and the blood lactate concentration in VOL+NMES were significantly greater than VOL at each exercise intensity (p < 0.05). Differences in oxygen consumption between VOL+NMES and VOL decreased with exercise intensity, and that at 125% VT was significantly lower than the net gain in oxygen consumption following NMES (p < 0.05). Differences in the blood lactate concentration between VOL+NMES and VOL increased with exercise intensity, and that at 50% VT was significantly lower than the net gain in the blood lactate concentration following NMES (p < 0.05). Our results suggest that voluntary exercise intensity has a critical impact on metabolic responses during the combined application of voluntary exercises and NMES. Superimposing NMES onto voluntary exercises at high exercise intensities may induce overlapping recruitment of motor units, leading to a markedly reduced benefit of additional metabolic responses on its superimposition.

Two weeks of single-leg immobilization alters intramyocellular lipid storage characteristics in healthy, young women.

Muscle disuse rapidly induces insulin resistance (IR). Despite a relationship between intramyocellular lipid (IMCL) content and IR, during muscle-disuse IR develops before IMCL accumulation, suggesting that IMCL are not related to disuse-induced IR. However, recent studies show that it is not total IMCL content, but IMCL size and location that are related to IR. Changes in these IMCL parameters may occur prior to increases in IMCL content, thus contributing to disuse-induced IR. Omega-3 fatty acids may mitigate the effects of disuse on IR by preventing a decline in insulin signaling proteins. Twenty women (age 22 ± 3 yr) received either 5 g·day-1 omega-3 fatty acid or isoenergetic sunflower oil for 4 wk prior to, throughout 2 wk of single-leg immobilization, and during 2 wk of recovery. Changes in IMCL characteristics and insulin signaling proteins were examined in vastus lateralis samples taken before supplementation and immobilization, and following immobilization and recovery. Omega-3 supplementation had no effect. IMCL area density decreased in the subsarcolemmal region during immobilization and recovery (-19% and -56%, respectively, P = 0.009). IMCL size increased in the central intermyofibrillar region during immobilization (43%, P = 0.007), returning to baseline during recovery. PLIN5 and AKT increased during immobilization (87%, P = 0.002; 30%, P = 0.007, respectively). PLIN 5 remained elevated and AKT increased further (15%) during recovery. IRS1, AS160, and GLUT4 decreased during immobilization (-35%, P = 0.001; -44%, P = 0.03; -56%, P = 0.02, respectively), returning to baseline during recovery. Immobilization alters IMCL storage characteristics while negatively affecting unstimulated insulin signaling protein content in young women.NEW & NOTEWORTHY We report that the subcellular storage location of IMCL is altered by limb immobilization, highlighting the need to evaluate IMCL storage location when assessing the effects of disuse on IMCL content. We also found that AKT content increased during immobilization in our female population, contrary to studies in males finding that AKT decreases during disuse, highlighting that men and women may respond differently to disuse and the necessity to include women in all research.

Daily protein supplementation attenuates immobilization-induced blunting of postabsorptive muscle mTORC1 activation in middle-aged men.

Disuse-induced muscle atrophy is accompanied by a blunted postprandial response of the mammalian target of rapamycin complex 1 (mTORC1) pathway. Conflicting observations exist as to whether postabsorptive mTORC1 pathway activation is also blunted by disuse and plays a role in atrophy. It is unknown whether changes in habitual protein intake alter mTORC1 regulatory proteins and how they may contribute to the development of anabolic resistance. The primary objective of this study was to characterize the downstream responsiveness of skeletal muscle mTORC1 activation and its upstream regulatory factors, following 14 days of lower limb disuse in middle-aged men (45-60 yr). The participants were further randomized to receive daily supplementation of 20 g/d of protein (n = 12; milk protein concentrate) or isocaloric carbohydrate placebo (n = 13). Immobilization reduced postabsorptive skeletal muscle phosphorylation of the mTORC1 downstream targets, 4E-BP1, P70S6K, and ribosomal protein S6 (RPS6), with phosphorylation of the latter two decreasing to a greater extent in the placebo, compared with the protein supplementation groups (37% ± 13% vs. 14% ± 11% and 38% ± 20% vs. 25% ± 8%, respectively). Sestrin2 protein was also downregulated following immobilization irrespective of supplement group, despite a corresponding increase in its mRNA content. This decrease in Sestrin2 protein was negatively correlated with the immobilization-induced change in the in silico-predicted regulator miR-23b-3p. No other measured upstream proteins were altered by immobilization or supplementation. Immobilization downregulated postabsorptive mTORC1 pathway activation, and 20 g/day of protein supplementation attenuated the decrease in phosphorylation of targets regulating muscle protein synthesis.

Enhanced dimethylarginine degradation improves coronary flow reserve and exercise tolerance in Duchenne muscular dystrophy carrier mice.

Duchenne muscular dystrophy (DMD) is an X-linked disease caused by null mutations in dystrophin and characterized by muscle degeneration. Cardiomyopathy is common and often prevalent at similar frequency in female DMD carriers irrespective of whether they manifest skeletal muscle disease. Impaired muscle nitric oxide (NO) production in DMD disrupts muscle blood flow regulation and exaggerates postexercise fatigue. We show that circulating levels of endogenous methylated arginines including asymmetric dimethylarginine (ADMA), which act as NO synthase inhibitors, are elevated by acute necrotic muscle damage and in chronically necrotic dystrophin-deficient mice. We therefore hypothesized that excessive ADMA impairs muscle NO production and diminishes exercise tolerance in DMD. We used transgenic expression of dimethylarginine dimethylaminohydrolase 1 (DDAH), which degrades methylated arginines, to investigate their contribution to exercise-induced fatigue in DMD. Although infusion of exogenous ADMA was sufficient to impair exercise performance in wild-type mice, transgenic DDAH expression did not rescue exercise-induced fatigue in dystrophin-deficient male mdx mice. Surprisingly, DDAH transgene expression did attenuate exercise-induced fatigue in dystrophin-heterozygous female mdx carrier mice. Improved exercise tolerance was associated with reduced heart weight and improved cardiac ß-adrenergic responsiveness in DDAH-transgenic mdx carriers. We conclude that DDAH overexpression increases exercise tolerance in female DMD carriers, possibly by limiting cardiac pathology and preserving the heart's responses to changes in physiological demand. Methylated arginine metabolism may be a new target to improve exercise tolerance and cardiac function in DMD carriers or act as an adjuvant to promote NO signaling alongside therapies that partially restore dystrophin expression in patients with DMD.NEW & NOTEWORTHY Duchenne muscular dystrophy (DMD) carriers are at risk for cardiomyopathy. The nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) is released from damaged muscle in DMD and impairs exercise performance. Transgenic expression of dimethylarginine dimethylaminohydrolase to degrade ADMA prevents cardiac hypertrophy, improves cardiac function, and improves exercise tolerance in DMD carrier mice. These findings highlight the relevance of ADMA to muscular dystrophy and have important implications for therapies targeting nitric oxide in patients with DMD and DMD carriers.

Influence of muscle oxygenation and nitrate-rich beetroot juice supplementation on O2 uptake kinetics and exercise tolerance.

We tested the hypothesis that acute supplementation with nitrate (NO3-)-rich beetroot juice (BR) would improve quadriceps muscle oxygenation, pulmonary oxygen uptake (V˙O2) kinetics and exercise tolerance (Tlim) in normoxia and that these improvements would be augmented in hypoxia and attenuated in hyperoxia. In a randomised, double-blind, cross-over study, ten healthy males completed two-step cycle tests to Tlim following acute consumption of 210 mL BR (18.6 mmol NO3-) or NO3--depleted beetroot juice placebo (PL; 0.12 mmol NO3-). These tests were completed in normobaric normoxia [fraction of inspired oxygen (FIO2): 21%], hypoxia (FIO2: 15%) and hyperoxia (FIO2: 40%). Pulmonary V˙O2 and quadriceps tissue oxygenation index (TOI), derived from multi-channel near-infrared spectroscopy, were measured during all trials. Plasma [nitrite] was higher in all BR compared to all PL trials (P < 0.05). Quadriceps TOI was higher in normoxia compared to hypoxia (P < 0.05) and higher in hyperoxia compared to hypoxia and normoxia (P < 0.05). Tlim was improved after BR compared to PL ingestion in the hypoxic trials (250 ± 44 vs. 231 ± 41 s; P = 0.006; d = 1.13), with the magnitude of improvement being negatively correlated with quadriceps TOI at Tlim (r = -0.78; P < 0.05). Tlim was not improved following BR ingestion in normoxia (BR: 364 ± 98 vs. PL: 344 ± 78 s; P = 0.087, d = 0.61) or hyperoxia (BR: 492 ± 212 vs. PL: 472 ± 196 s; P = 0.273, d = 0.37). BR ingestion increased peak V˙O2 in hypoxia (P < 0.05), but not normoxia or hyperoxia (P > 0.05). These findings indicate that BR supplementation is more likely to improve Tlim and peak V˙O2 in situations when skeletal muscle is more hypoxic.

Comparative pharmacokinetic and biodistribution study of two distinct squalene-containing oil-in-water emulsion adjuvants in H5N1 influenza vaccines.

BACKGROUND: In recent years, there has been great interest from academia, industry and government scientists for an increased understanding of the mode of action of vaccine adjuvants to characterize the safety and efficacy of vaccines. In this context, pharmacokinetic (PK) and biodistribution studies are useful for quantifying the concentration of vaccine adjuvants in mechanistically or toxicologically relevant target tissues. METHODS: In this study, we conducted a comparative analysis of the PK and biodistribution profile of radiolabeled squalene for up to 336 h (14 days) after intramuscular injection of mice with adjuvanted H5N1 influenza vaccines. The evaluated adjuvants included an experimental-grade squalene-in-water (SQ/W) emulsion (AddaVax®) and an adjuvant system (AS03®) that contained squalene and α-tocopherol in the oil phase of the emulsion. RESULTS: The half-life of the initial exponential decay from quadriceps muscle was 1.5 h for AS03 versus 12.9 h for AddaVax. At early time points (1-6 h), there was about a 10-fold higher concentration of labeled squalene in draining lymph nodes following AS03 injection compared to AddaVax. The area-under-concentration curve up to 336 h (AUC0-336hr) and peak concentration of squalene in spleen (immune organ) was about 1.7-fold higher following injection of AS03 than AddaVax. The peak systemic tissue concentration of squalene from the two adjuvants, with or without antigen, remained below 1% of injected dose for toxicologically relevant target tissues, such as spinal cord, brain, and kidney. The pharmacokinetics of AS03 was unaffected by the presence of H5N1 antigen. CONCLUSIONS: This study demonstrates a rapid decline of AS03 from the quadriceps muscles of mice as compared to conventional SQ/W emulsion adjuvant, with an increased transfer to mechanistically relevant tissues such as local lymph nodes. Systemic tissue exposure to potential toxicological target tissues was very low.

Effects of acute nitric oxide precursor intake on peripheral and central fatigue during knee extensions in healthy men.

NEW FINDINGS: What is the central question of this study? What is the effect of acute NO precursor intake on vascular function, muscle and cerebral oxygenation and peripheral and central neuromuscular fatigue during knee-extension exercise? What is the main finding and its importance? Acute NO precursor ingestion increases the plasma concentrations of NO precursors (nitrate, arginine and citrulline) and enhances post-ischaemic vasodilatation, but has no significant effect on muscle and cerebral oxygenation, peripheral and central mechanisms of neuromuscular fatigue and, consequently, does not improve exercise performance. ABSTRACT: Nitric oxide (NO) plays an important role in matching blood flow to oxygen demand in the brain and contracting muscles during exercise. Previous studies have shown that increasing NO bioavailability can improve muscle function. The aim of this study was to assess the effect of acute NO precursor intake on muscle and cerebral oxygenation and on peripheral and central neuromuscular fatigue during exercise. In four experimental sessions, 15 healthy men performed a thigh ischaemia-reperfusion test followed by submaximal isometric knee extensions (5 s on-4 s off; 45% of maximal voluntary contraction) until task failure. In each session, subjects drank a nitrate-rich beetroot juice containing 520 mg nitrate (N), N and citrulline (6 g; N+C), N and arginine (6 g; N+A) or a placebo (PLA). Prefrontal cortex and quadriceps near-infrared spectroscopy parameters were monitored continuously. Transcranial magnetic stimulation and femoral nerve electrical stimulation were used to assess central and peripheral determinants of fatigue. The post-ischaemic increase in thigh blood total haemoglobin concentration was larger in N (10.1 ± 3.7 mmol) and N+C (10.9 ± 3.3 mmol) compared with PLA (8.2 ± 2.7 mmol; P < 0.05). Nitric oxide precursors had no significant effect on muscle and cerebral oxygenation or on peripheral and central mechanisms of neuromuscular fatigue during exercise. The total number of knee extensions did not differ between sessions (N, 71.9 ± 33.2; N+A, 73.3 ± 39.4; N+C, 74.6 ± 34.0; PLA, 71.8 ± 39.9; P > 0.05). In contrast to the post-ischaemic hyperaemic response, NO bioavailability in healthy subjects might not be the limiting factor for tissue perfusion and oxygenation during submaximal knee extensions to task failure.

Omega-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy during two weeks of unilateral leg immobilization in healthy young women.

Omega-3 (n-3) fatty acid supplementation enhances muscle protein synthesis and muscle size. Whether n-3 fatty acid supplementation attenuates human muscle disuse atrophy is unknown. We determined the influence of n-3 fatty acid supplementation on muscle size, mass, and integrated rates of myofibrillar protein synthesis (MyoPS) following 2 wk of muscle disuse and recovery in women. Twenty women (BMI = 23.0 ± 2.3 kg/m2, age = 22 ± 3 yr) underwent 2 wk of unilateral limb immobilization followed by 2 wk of return to normal activity. Starting 4 wk prior to immobilization, participants consumed either 5 g/d of n-3 fatty acid or an isoenergetic quantity of sunflower oil (control). Muscle size and mass were measured pre- and postimmobilization, and after recovery. Serial muscle biopsies were obtained to measure integrated (daily) MyoPS. Following immobilization, the decline in muscle volume was greater in the control group compared to the n-3 fatty acid group (14 vs. 8%, P < 0.05) and was not different from preimmobilization at recovery in the n-3 fatty acid group; however, it was still lower in the control group ( P < 0.05). Muscle mass was reduced in the control group only ( P < 0.05). MyoPS was higher in the n-3 group compared with the control group at all times ( P < 0.05). We conclude that n-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy in young women, which may be mediated by higher rates of MyoPS.-McGlory, C., Gorissen, S. H. M., Kamal, M., Bahniwal, R., Hector, A. J., Baker, S. K., Chabowski, A., Phillips, S. M. Omega-3 fatty acid supplementation attenuates skeletal muscle disuse atrophy during two weeks of unilateral leg immobilization in healthy young women.

Effects of light-emitting diode therapy (LEDT) on cardiopulmonary and hemodynamic adjustments during aerobic exercise and glucose levels in patients with diabetes mellitus: A randomized, crossover, double-blind and placebo-controlled clinical trial.

The aim of this study was to evaluate the acute effects of light-emitting diode therapy (LEDT) on cardiopulmonary adjustments and muscle oxygenation dynamics during transition to moderate exercise, as well as in glucose and lactate levels in patients with type 2 diabetes mellitus (T2DM). Sixteen individuals with T2DM (age 55.1±5.4 years) performed four separate tests receiving LEDT or placebo in random order, at intervals of at least 14 days. A light-emitting diode array (50GaAIAs LEDs, 850nm, 75mW per diode) was used to perform LEDT bilaterally on the quadriceps femoris and triceps surae muscles for 40s at each site. After, a moderate cycling exercise was performed and oxygen uptake, muscular deoxyhemoglobin, heart rate and cardiac output were measured. Lactate and glucose levels were measured before LEDT/placebo and after the exercise. The LEDT decreased the glucose levels after the exercise compared with values before LEDT (173.7±61.0 to 143.5±53.5 mg/dl, P=0.02) and it did not affect the cardiopulmonary and hemodynamic adjustments in exercise, as well as lactate levels in both groups. In conclusion, the LEDT in combination with moderate exercise acutely decreased the glucose levels in men with T2DM.

The effects of beetroot juice supplementation on exercise economy, rating of perceived exertion and running mechanics in elite distance runners: A double-blinded, randomized study.

PURPOSE: Nitrate-rich beetroot juice supplementation has been extensively used to increase exercise economy in different populations. However, its use in elite distance runners, and its potential effects on biomechanical aspects of running have not been properly investigated. This study aims to analyze the potential effects of 15 days of beetroot juice supplementation on physiological, psychological and biomechanical variables in elite runners. METHODS: Twelve elite middle and long-distance runners (age = 26.3 ± 5.1yrs, VO2Max = 71.8±5.2 ml*kg-1*min-1) completed an incremental running test to exhaustion on a treadmill before and after a 15-days supplementation period, in which half of the group (EG) consumed a daily nitrate-rich beetroot juice and the other group (PG) consumed a placebo drink. Time to exhaustion (TEx), running economy, vastus lateralis oxygen saturation (SmO2), leg stiffness and rate of perceived exertion (RPE) were measured at 15, 17.1 and 20 km/h during the incremental test. RESULTS: Likely to very likely improvements in EG were observed for the RPE (Standardized mean difference (SMD) = -2.17, 90%CI = -3.23, -1.1), SmO2 (SMD = 0.72, 90%CI = 0.03, 1.41) and TEx (SMD = 1.18, 90%CI = -0.14, 2.5) in comparison with PG. No other physiological or biomechanical variable showed substantial improvements after the supplementation period. CONCLUSIONS: Fifteen days of nitrate-rich beetroot juice supplementation produced substantial improvements in the time to exhaustion in elite runners; however, it didn't produce meaningful improvements in running economy, VO2Max or mechanical parameters.

Resistance Exercise Selectively Mobilizes Monocyte Subsets: Role of Polyphenols.

PURPOSE: To examine the impact of polyphenol supplementation on the recruitment, mobilization, and activation of monocyte subsets after resistance exercise. METHODS: Thirty-eight recreationally active males (22.1 ± 3.1 yr; 173.9 ± 7.9 cm; 77.8 ± 14.5 kg) were assigned to 28 d of polyphenol blend (PPB) supplementation, placebo (PL), or control (CON). Blood samples were obtained before (PRE) postresistance exercise, immediately (IP) postresistance exercise, 1 h (1H) postresistance exercise, 5 h (5H) postresistance exercise, 24 h (24H) postresistance exercise, and 48 h (48H) postresistance exercise (PPB/PL) or rest (CON). Fine-needle biopsies were obtained from the vastus lateralis at PRE, 1H, 5H, and 48H. Circulating concentrations of macrophage chemoattractant protein-1 (MCP-1) and fractalkine, as well as intramuscular MCP-1 were analyzed via multiplex assay. Changes in the proportions and expression of CD11b on monocyte subsets were assessed via flow cytometry. RESULTS: Circulating MCP-1 increased in PPB and PL at IP with further increases at 5H. Intramuscular MCP-1 was increased at 1H, 5H, and 48H in all groups. Classical monocyte proportions were reduced in PPB and PL at IP, and increased at 1H. Nonclassical monocytes were increased in PPB and PL at IP, whereas intermediate monocytes were increased at IP, and reduced at 1H. Intermediate monocytes were increased in PPB at 24H and 48H. CD11b expression was reduced on PPB compared with PL and CON at PRE on intermediate and nonclassical monocytes. CONCLUSIONS: Resistance exercise may elicit selective mobilization of intermediate monocytes at 24H and 48H, which may be mediated by tissue damage. Additionally, polyphenol supplementation may suppress CD11b expression on monocyte subsets at rest.

High-Frequency Neuromuscular Electrical Stimulation Increases Anabolic Signaling.

PURPOSE: Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation settings to increase muscle mass and strength. However, the effects of NMES on muscle growth are not clear and no human studies have compared anabolic signaling between low-frequency (LF) and high-frequency (HF) NMES. The purpose of this study was to determine the skeletal muscle anabolic signaling response to an acute bout of LF- and HF-NMES. METHODS: Eleven young healthy volunteers (6 men, 5 women) received an acute bout of LF-NMES (20 Hz) and HF-NMES (60 Hz). Muscle biopsies were obtained from the vastus lateralis muscle before the first NMES treatment and 30 min after each NMES treatment. Phosphorylation of the following key anabolic signaling proteins was measured by Western blot, and proteins are expressed as a ratio of phosphorylated to total: mammalian target of rapamycin, p70-S6 kinase 1, and eukaryotic initiation factor 4E binding protein 1. RESULTS: Compared with pre-NMES, phosphorylation of mammalian target of rapamycin was upregulated 40.2% for LF-NMES (P = 0.018) and 68.4% for HF-NMES (P < 0.0001), and HF-NMES was 29.3% greater than LF-NMES (P = 0.026). Phosphorylation of p70-S6 kinase 1 after HF-NMES was 96.6% higher than pre-NMES (P = 0.001) and was not different between pre-NMES and LF-NMES (although it was 50.4% higher after LF-NMES) or LF- and HF-NMES (P > 0.05). There were no differences between treatment conditions for eukaryotic initiation factor 4E binding protein 1 phosphorylation (P > 0.05). CONCLUSIONS: An acute bout of LF- and HF-NMES upregulated anabolic signaling with HF-NMES producing a greater anabolic response compared with LF-NMES, suggesting that HF stimulation may provide a stronger stimulus for processes that initiate muscle hypertrophy. In addition, the stimulation frequency parameter should be considered by clinicians in the design of optimal NMES treatment protocols.

Paralytic and nonparalytic muscle adaptations to exercise training versus high-protein diet in individuals with long-standing spinal cord injury.

This study compares the effects of an 8-wk isocaloric high-protein (HP) diet versus a combination exercise (Comb-Ex) regimen on paralytic vastus lateralis (VL) and nonparalytic deltoid muscle in individuals with long-standing spinal cord injury (SCI). Fiber-type distribution, cross-sectional area (CSA), levels of translation initiation signaling proteins (Erk-1/2, Akt, p70S6K1, 4EBP1, RPS6, and FAK), and lean thigh mass were analyzed at baseline and after the 8-wk interventions. A total of 11 participants (C5-T12 levels, 21.8 ± 6.3 yr postinjury; 6 Comb-Ex and 5 HP diet) completed the study. Comb-Ex training occurred 3 days/wk and consisted of upper body resistance training (RT) in addition to neuromuscular electrical stimulation (NMES)-induced-RT for paralytic VL muscle. Strength training was combined with high-intensity arm-cranking exercises (1-min intervals at 85-90%, V̇o2peak) for improving cardiovascular endurance. For the HP diet intervention, protein and fat each comprised 30%, and carbohydrate comprised 40% of total energy. Clinical tests and muscle biopsies were performed 24 h before and after the last exercise or diet session. The Comb-Ex intervention increased Type IIa myofiber distribution and CSA in VL muscle and Type I and IIa myofiber CSA in deltoid muscle. In addition, Comb-Ex increased lean thigh mass, V̇o2peak, and upper body strength ( P < 0.05). These results suggest that exercise training is required to promote favorable changes in paralytic and nonparalytic muscles in individuals with long-standing SCI, and adequate dietary protein consumption alone may not be sufficient to ameliorate debilitating effects of paralysis. NEW & NOTEWORTHY This study is the first to directly compare the effects of an isocaloric high-protein diet and combination exercise training on clinical and molecular changes in paralytic and nonparalytic muscles of individuals with long-standing spinal cord injury. Our results demonstrated that muscle growth and fiber-type alterations can best be achieved when the paralyzed muscle is sufficiently loaded via neuromuscular electrical stimulation-induced resistance training.

Human skeletal muscle contains no detectable guanidinoacetic acid.

We analyzed data from previously completed trials to determine the effects of supplemental guanidinoacetic acid (GAA) on markers of muscle bioenergetics in healthy men using 1.5 T magnetic resonance spectroscopy. No detectable GAA (<0.1 µmol/L) was found in the vastus medialis muscle at baseline nor at follow-up. This implies deficient GAA availability in the human skeletal muscle, suggesting absent or negligible potential for creatine synthesis from GAA inside this tissue, even after GAA loading.

Protein ingestion preserves proteasome activity during intense aseptic inflammation and facilitates skeletal muscle recovery in humans.

The ubiquitin-proteasome system (UPS) is the main cellular proteolytic system responsible for the degradation of normal and abnormal (e.g. oxidised) proteins. Under catabolic conditions characterised by chronic inflammation, the UPS is activated resulting in proteolysis, muscle wasting and impaired muscle function. Milk proteins provide sulphur-containing amino acid and have been proposed to affect muscle inflammation. However, the response of the UPS to aseptic inflammation and protein supplementation is largely unknown. The aim of this study was to investigate how milk protein supplementation affects UPS activity and skeletal muscle function under conditions of aseptic injury induced by intense, eccentric exercise. In a double-blind, cross-over, repeated measures design, eleven men received either placebo (PLA) or milk protein concentrate (PRO, 4×20 g on exercise day and 20 g/d for the following 8 days), following an acute bout of eccentric exercise (twenty sets of fifteen eccentric contractions at 30°/s) on an isokinetic dynamometer. In each trial, muscle biopsies were obtained from the vastus lateralis muscle at baseline, as well as at 2 and 8 d post exercise, whereas blood samples were collected before exercise and at 6 h, 1 d, 2 d and 8 d post exercise. Muscle strength and soreness were assessed before exercise, 6 h post exercise and then daily for 8 consecutive days. PRO preserved chymotrypsin-like activity and attenuated the decrease of strength, facilitating its recovery. PRO also prevented the increase of NF-κB phosphorylation and HSP70 expression throughout recovery. We conclude that milk PRO supplementation following exercise-induced muscle trauma preserves proteasome activity and attenuates strength decline during the pro-inflammatory phase.

Neuromuscular Electrical Stimulation and Anabolic Signaling in Patients with Stroke.

INTRODUCTION: Stroke results in limited ability to produce voluntary muscle contraction and movement on one side of the body, leading to further muscle wasting and weakness. Neuromuscular electrical stimulation is often used to facilitate involuntary muscle contraction; however, the effect of neuromuscular electrical stimulation on muscle growth and strengthening processes in hemiparetic muscle is not clear. This study examined the skeletal muscle anabolic response of an acute bout of neuromuscular electrical stimulation in individuals with chronic stroke and healthy older adults. METHODS: Eleven individuals (59.8 ± 2.7 years old) were divided into a chronic stroke group (n = 5) and a healthy older adult control group (n = 6). Muscle biopsies were obtained before and after stimulation from the vastus lateralis of the hemiparetic leg for the stroke group and the right leg for the control group. The neuromuscular electrical stimulation protocol consisted of a 60-minute, intermittent stimulation train at 60 Hz. Phosphorylation of mammalian target of rapamycin and ribosomal protein S6 kinase beta-1 were analyzed by Western blot. FINDINGS: An acute bout of neuromuscular electrical stimulation increased phosphorylation of mammalian target of rapamycin (stroke: 56.0%; control: 51.4%; P = .002) and ribosomal protein S6 kinase beta-1 (stroke: 131.2%; control: 156.3%; P = .002) from resting levels to post-neuromuscular electrical stimulation treatment, respectively. Phosphorylated protein content was similar between stroke and control groups at both time points. CONCLUSION: Findings suggest that paretic muscles of patients with chronic stroke may maintain ability to stimulate protein synthesis machinery in response to neuromuscular electrical stimulation.