Characterisation of the Muscle Protein Synthetic Response to Resistance Exercise in Healthy Adults: A Systematic Review and Exploratory Meta-Analysis.

Methods: Five electronic databases (PubMed (Medline), Web of Science, Embase, Sport Discus, and Cochrane Library) were searched for controlled trials that assessed the MPS response to RE in healthy, adult humans, postabsorptive state. Individual study and random-effects meta-analysis arewere used to inform the effects of RE and covariates on MPS. Results from 79 controlled trials with 237 participants were analysed. Results: Analysis of the pooled effects revealed robust increases in MPS following RE (weighted mean difference (WMD): 0.032% h-1, 95% CI: [0.024, 0.041] % h-1, I2 = 92%, k = 37, P < 0.001). However, the magnitude of the increase in MPS was lower in older adults (>50 y: WMD: 0.015% h-1, 95% CI: [0.007, 0.022] % h-1, I2 = 76%, k = 12, P = 0.002) compared to younger adults (<35 y: WMD: 0.041% h-1, 95% CI: [0.030, 0.052] % h-1, I2 = 88%, k = 25, P < 0.001). Individual studies have reported that the temporal proximity of the RE, muscle group, muscle protein fraction, RE training experience, and the loading parameters of the RE (i.e., intensity, workload, and effort) appeared to affect the MPS response to RE, whereas sex or type of muscle contraction does not. Conclusion: A single bout of RE can sustain measurable increases in postabsorptive MPS soon after RE cessation and up to 48 h post-RE. However, there is substantial heterogeneity in the magnitude and time course of the MPS response between trials, which appears to be influenced by participants' age and/or the loading parameters of the RE itself.

An Investigation of the Protein Quality and Temporal Pattern of Peripheral Blood Aminoacidemia following Ingestion of 0.33 g·kg-1 Body Mass Protein Isolates of Whey, Pea, and Fava Bean in Healthy, Young Adult Men.

An increase in the intake of legumes is recommended in the promotion of plant-sourced (PSP) rather than animal-sourced (ASP) protein intake to produce a more sustainable diet. This study evaluated the quality of novel PSP isolates from pea (PEA) and fava bean (FAVA) and an ASP isolate of whey (WHEY) and compared the magnitude and temporal pattern of peripheral arterial aminoacidemia following ingestion of 0.33 g·kg-1 body mass of protein isolate in healthy young adult men (n = 9). Total indispensable amino acids (IAA) comprised 58% (WHEY), 46% (PEA), and 42% (FAVA) of the total amino acid (AA) composition, with the ingested protein providing 108% (WHEY), 77% (PEA), and 67% (FAVA) of the recommended per diem requirement of IAA. Reflecting the AA composition, the area under the curve (∆AUC0-180), post-ingestion increase in total IAA for WHEY was 41% (p < 0.001) and 57% (p < 0.001) greater than PEA and FAVA, respectively, with PEA exceeding FAVA by 28% (p = 0.003). As a sole-source, single-dose meal-size serving, the lower total IAA for PEA and FAVA would likely evoke a reduced post-prandial anabolic capacity compared to WHEY. Incorporated into a food matrix, the promotion of PSP isolates contributes to a more sustainable diet.

The Effect of Fava Bean (Vicia faba L.) Protein Ingestion on Myofibrillar Protein Synthesis at Rest and after Resistance Exercise in Healthy, Young Men and Women: A Randomised Control Trial.

The aim of the present study was to evaluate the effect of feeding fava bean (Vicia faba L.) protein (FBP) on resting and post-exercise myofibrillar fractional synthetic rate (myoFSR). In a parallel, double-blind, randomised control trial, sixteen young, healthy recreationally active adults (age = 25 (5) years, body mass = 70 (15) kg, stature = 1.72 (0.11) m, mean (SD)) ingested 0.33 g·kg-1 FBP (n = 8) or a negative control (CON, i.e., EAA-free mixture) (n = 8), immediately after a bout of unilateral knee-extensor resistance exercise. Plasma, saliva, and m. vastus lateralis muscle samples were obtained pre-ingestion and 3 h post-ingestion. MyoFSR was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Pyr-IRMS). Resistance exercise increased myoFSR (p = 0.012). However, ingestion of FBP did not evoke an increase in resting (FBP 29 [-5, 63] vs. CON 12 [-25, 49]%, p = 0.409, mean % change [95% CI]) or post-exercise (FBP 78 [33, 123]% vs. CON 58 [9, 107]%, p = 0.732) myoFSR. Ingestion of 0.33 g·kg-1 of FBP does not appear to enhance resting or post-exercise myoFSR in young, healthy, recreationally active adults.

The Influence of Maximal Strength and Knee Angle on the Reliability of Peak Force in the Isometric Squat.

This study aimed to investigate the test-retest reliability of peak force in the isometric squat across the strength spectrum using coefficient of variation (CV) and intra-class correlation coefficient (ICC). On two separate days, 59 healthy men (mean (SD) age 23.0 (4.1) years; height 1.79 (0.7) m; body mass 84.0 (15.2) kg) performed three maximal effort isometric squats in two positions (at a 120° and a 90° knee angle). Acceptable reliability was observed at both the 120° (CV = 7.5 (6.7), ICC = 0.960 [0.933, 0.977]) and 90° positions (CV = 9.2 (8.8), ICC = 0.920 [0.865, 0.953]). There was no relationship between peak force in the isometric squat and the test-retest reliability at either the 120° (r = 0.052, p = 0.327) or 90° (r = 0.014, p = 0.613) positions. A subgroup of subjects (n = 17) also completed the isometric squat test at a 65° knee angle. Acceptable reliability was observed in this position (CV = 9.6 (9.3), ICC = 0.916 [0.766, 0.970]) and reliability was comparable to the 120° and 90° positions. Therefore, we deem isometric squat peak force output to be a valid and reliable measure across the strength spectrum and in different isometric squat positions.

Separating the Wheat from the Chaff: Nutritional Value of Plant Proteins and Their Potential Contribution to Human Health.

The quality and nutritional value of dietary proteins are determined by the quantity, digestibility and bioavailability of essential amino acids (EAA), which play a critical role in human growth, longevity and metabolic health. Plant-source protein is often deficient in one or more EAAs (e.g., branched-chain amino acids, lysine, methionine and/or tryptophan) and, in its natural form, is less digestible than animal-source protein. Nevertheless, dietary intake of plant-source protein has been promoted because of its potential health benefits, lower cost of production and lower environmental impact compared to animal-source protein. Implementation of dietary strategies that improve both human and planetary health are of critical importance and subject to growing interest from researchers and consumers. Therefore, in this review we analyse current plant protein intake patterns and discuss possible countermeasures that can enhance plant protein nutrition, examples include: (1) combining different plant proteins with complementary EAA profiles; (2) identification and commercial cultivation of new and novel high-quality plant proteins; (3) industrial and domestic processing methods; and (4) genome-editing techniques.

The Effect of Whey Protein Supplementation on Myofibrillar Protein Synthesis and Performance Recovery in Resistance-Trained Men.

BACKGROUND: The aim of this study was to investigate the effect of whey protein supplementation on myofibrillar protein synthesis (myoPS) and muscle recovery over a 7-d period of intensified resistance training (RT). METHODS: In a double-blind randomised parallel group design, 16 resistance-trained men aged 18 to 35 years completed a 7-d RT protocol, consisting of three lower-body RT sessions on non-consecutive days. Participants consumed a controlled diet (146 kJ·kg-1·d-1, 1.7 g·kg-1·d-1 protein) with either a whey protein supplement or an isonitrogenous control (0.33 g·kg-1·d-1 protein). To measure myoPS, 400 ml of deuterium oxide (D2O) (70 atom %) was ingested the day prior to starting the study and m. vastus lateralis biopsies were taken before and after RT-intervention. Myofibrillar fractional synthetic rate (myoFSR) was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Pyr-IRMS). Muscle recovery parameters (i.e., countermovement jump height, isometric-squat force, muscle soreness and serum creatine kinase) were assessed daily. RESULTS: MyoFSR PRE was 1.6 (0.2) %∙d-1 (mean (SD)). Whey protein supplementation had no effect on myoFSR (p = 0.771) or any recovery parameter (p = 0.390-0.989). CONCLUSIONS: Over an intense 7-d RT protocol, 0.33 g·kg-1·d-1 of supplemental whey protein does not enhance day-to-day measures of myoPS or postexercise recovery in resistance-trained men.

A cell-based evaluation of a non-essential amino acid formulation as a non-bioactive control for activation and stimulation of muscle protein synthesis using ex vivo human serum.

PURPOSE: The purpose of this study was to compare the effect of treating skeletal muscle cells with media conditioned by postprandial ex vivo human serum fed with either isonitrogenous Non-Essential Amino Acid (NEAA) or a whey protein hydrolysate (WPH) on stimulating Muscle Protein Synthesis (MPS) in C2C12 skeletal muscle cells. METHODS: Blood was taken from six young healthy males following overnight fast (fasted) and 60 min postprandial (fed) ingestion of either WPH or NEAA (0.33 g.kg-1 Body Mass). C2C12 myotubes were treated with media conditioned by ex vivo human serum (20%) for 4 h. Activation of MPS signalling (phosphorylation of mTOR, P70S6K and 4E-BP1) were determined in vitro by Western Blot and subsequent MPS were determined in vitro by Western Blot and surface sensing of translation technique (SUnSET) techniques, respectively. RESULTS: Media conditioned by NEAA fed serum had no effect on protein signalling or MPS compared to fasted, whereas media conditioned by WPH fed serum significantly increased mTOR (Ser2448), P70S6K and 4E-BP1 phosphorylation (p<0.01, p<0.05) compared to fasted serum. Furthermore, the effect of media conditioned by WPH fed serum on protein signalling and MPS was significantly increased (p<0.01, p<0.05) compared to NEAA fed serum. CONCLUSION: In summary, media conditioned by NEAA fed serum did not result in activation of MPS. Therefore, these in vitro findings suggest the use of isonitrogenous NEAA acts as an effective control for comparing bioactivity of different proteins on activation of MPS.

Differential Stimulation of Post-Exercise Myofibrillar Protein Synthesis in Humans Following Isonitrogenous, Isocaloric Pre-Exercise Feeding.

The aim of this study was to test the effects of two disparate isonitrogenous, isocaloric pre-exercise feeds on deuterium-oxide (D2O) derived measures of myofibrillar protein synthesis (myoPS) in humans. Methods: In a double-blind parallel group design, 22 resistance-trained men aged 18 to 35 years ingested a meal (6 kcal·kg-1, 0.8 g·kg-1 carbohydrate, 0.2 g·kg-1 fat) with 0.33 g·kg-1 nonessential amino acids blend (NEAA) or whey protein (WHEY), prior to resistance exercise (70% 1RM back-squats, 10 reps per set to failure, 25% duty cycle). Biopsies of M. vastus lateralis were obtained pre-ingestion (PRE) and +3 h post-exercise (POST). The myofibrillar fractional synthetic rate (myoFSR) was calculated via deuterium labelling of myofibrillar-bound alanine, measured by gas chromatography-pyrolysis-isotope ratio mass spectrometry (GC-Pyr-IRMS). Data are a mean percentage change (95% CI). Results: There was no discernable change in myoFSR following NEAA (10(-5, 25) %, p = 0.235), whereas an increase in myoFSR was observed after WHEY (28 (13, 43) %, p = 0.003). Conclusions: Measured by a D2O tracer technique, a disparate myoPS response was observed between NEAA and WHEY. Pre-exercise ingestion of whey protein increased post-exercise myoPS, whereas a NEAA blend did not, supporting the use of NEAA as a viable isonitrogenous negative control.

Regulation of GLUT4 translocation in an in vitro cell model using postprandial human serum ex vivo.

NEW FINDINGS: What is the research question? This study used a new experimental model, in which culture medium is conditioned with human serum ex vivo, to investigate nutrient-mediated regulation of GLUT4 translocation in skeletal muscle cells in vitro. What is the main finding and importance? Human serum stimulated GLUT4 translocation, an effect differentially modulated by whether the culture medium was conditioned with serum from fasted subjects or with serum collected after feeding of intact or hydrolysed whey protein. Conditioning cell culture medium with human serum ex vivo represents a new approach to elucidate the effects of ingesting specific nutrients on skeletal muscle cell metabolism. ABSTRACT: Individual amino acids, amino acid mixtures and protein hydrolysates stimulate glucose uptake in many experimental models. To replicate better in vitro the dynamic postprandial response to feeding in vivo, in the present study we investigated the effects of culture media conditioned with fasted and postprandial human serum on GLUT4 translocation in L6-GLUT4myc myotubes. Serum samples were collected from healthy male participants (n = 8) at baseline (T0), 60 (T60) and 120 min (T120) after the ingestion of 0.33 g (kg body mass)-1 of intact (WPC) or hydrolysed (WPH) whey protein and an isonitrogenous non-essential amino acid (NEAA) control. L6-GLUT4myc myotubes were starved of serum and amino acids for 1 h before incubation for 1 h in medium containing 1% postprandial human serum, after which GLUT4 translocation was determined via colorimetric assay. Medium conditioned with fasted human serum at concentrations of 5-20% increased cell surface GLUT4myc abundance. Incubation with serum collected after the ingestion of WPH increased cell surface GLUT4myc at T60 relative to T0 [mean (lower, upper 95% confidence interval)]; [1.13 (1.05, 1.22)], whereas WPC [0.98 (0.90, 1.07)] or NEAA [1.02 (0.94, 1.11)] did not. The differential increases in cell surface GLUT4myc abundance were not explained by differences in serum concentrations of total, essential and branched-chain amino acids or insulin, glucagon-like peptide 1 (GLP-1) and gastric inhibitory polypeptide (GIP). Using a new ex vivo, in vitro approach, cell culture medium conditioned with postprandial serum after the ingestion of a whey protein hydrolysate increased GLUT4 translocation in skeletal muscle cells.

Sex Differences in the Temporal Recovery of Neuromuscular Function Following Resistance Training in Resistance Trained Men and Women 18 to 35 Years.

To investigate sex differences in the temporal recovery of neuromuscular function following resistance training (RT), eleven men and eight women 18-35 years completed a single RT bout (barbell back-squats, 80 % 1RM, 5 sets × 5 reps, 25 % duty cycle, then 1 set × max reps). Measures of muscle function (isometric, concentric, eccentric knee extensor strength, and countermovement jump (CMJ) height), serum creatine kinase activity (CK) and lower-body muscle pain were assessed before RT (0 h), +4 h, +24 h, +48 h, and +72 h post-RT. Data are mean % change from PRE (SD) and effect size (ω2, d). Men and women had similar RT-experience (men, 2.1 (0.8) years vs. women 2.4 (1.0) years, P = 0.746, and d = 0.3) and 1RM strength per kg lean mass (men, 1.9 (0.2) kg⋅kg-1 vs. women, 1.8 (0.3) kg⋅kg-1, P = 0.303, and d = 0.3). A 36 (12)% increase in lower-body muscle pain was reported following RT (P < 0.05, d > 0.9). There was an absence of any overt change in CK [+24 h, 74 (41) IU⋅L-1; pooled mean (SD)]. Decrements in knee extensor strength and CMJ height were observed +4 to +72 h for both men and women (P < 0.05, ω2 = 0.19-0.69). Sex differences were apparent for CMJ height (+24 h men, -10 (6)% vs. women, -20 (11)%, P < 0.001, and d = 1.8) and isokinetic concentric strength (+24 h men, -10 (13)% vs. women -25 (14)%, P = 0.006, and d = 1.8), with a more pronounced loss and prolonged recovery in women compared to men (e.g., CMJ + 72 h men, -3 (6)% vs. women, -13 (12)%, P = 0.051, and d = 1.1). We conclude that the different temporal recovery patterns between men and women are not explicable by differences in muscle strength, RT performance, experience, muscle damage or fatigability.

Acute reduction of lower-body contractile function following a microbiopsy of m. vastus lateralis.

Twenty-three resistance trained men 18-35 years (23 [3] years, 1.8 [0.1] m, 81 [10] kg body mass, 2.3 [1.1] years resistance training experience; mean [SD]) performed repeated maximal voluntary isometric squats (ISQ) and countermovement jumps (CMJ) pre- and +30 minutes post a unilateral microbiopsy of m. vastus lateralis. ISQ and CMJ were simultaneously measured by two force plates sampling ipsilateral (biopsied) and contralateral (non-biopsied) limb force. Bilateral limb force (ipsilateral + contralateral) and imbalance (ipsilateral/bilateral) data are reported as % change from pre-biopsy (mean [95% CI]). A post-biopsy reduction in bilateral ISQ peak force (-17 [-23, -11] %; P < 0.001), ISQ rate of force development (RFD; -28 [-41, -15] %, P = 0.002) and CMJ peak take-off force (-7 [-13, -1]%, P = 0.019) occurred. Imbalance was observed for ISQ peak force (3.2 [2.1, 4.3] %, P < 0.001), RFD (2.8 [1.6, 4.0] %, P < 0.001) and CMJ landing (3.3 [1.0, 5.6] %, P = 0.009), resultant of a force transfer from the ipsilateral (biopsied) to the contralateral (non-biopsied) limb. These data suggest that in young, resistance trained men a modulatory influence on maximal voluntary static and dynamic lower-body contractile function is evoked acutely (+30 minutes) following a microbiopsy of m. vastus lateralis.

Regulation of muscle protein synthesis in an in vitro cell model using ex vivo human serum.

NEW FINDINGS: What is the central question of this study? Can medium conditioned by ex vivo human serum regulate muscle protein synthesis in skeletal muscle cells in vitro? What is the main finding and its importance? This study demonstrates that medium conditioned by ex vivo human serum can regulate muscle protein synthesis in skeletal muscle cells in vitro via the mammalian Target of Rapomycin (mTOR) pathway, and this can be regulated differentially by fed and fasted ex vivo human serum. ABSTRACT: Human serum embodies the integrated systemic response to any condition or perturbation, which may regulate muscle protein synthesis (MPS). Conditioning of medium with human serum represents a physiologically relevant method of regulating MPS in vitro. The primary purpose of the study was the development of a model using ex vivo human serum to condition medium and regulate MPS in in vitro skeletal muscle cells. Four young healthy men reported to the laboratory after an overnight fast and were fed with 0.33 g (kg body mass)-1 whey protein. Blood samples were taken before (Fasted) and 60 min postprandial (Fed). Fully differentiated C2C12 skeletal muscle cells were nutrient and serum deprived for 1 h and subsequently treated with medium conditioned with Fasted or Fed ex vivo human serum (20%) for 4 h. The MPS was measured using the surface sensing of translation technique and activation of mTOR, P70S6K and 4EBP1 by Western blot. Fasted and fed ex vivo human serum increased MPS (P < 0.05). Although a strong effect (ƞ2  = 0.36) for increased MPS in Fed relative to Fasted was observed, this was not statistically significant (P > 0.05). Activation of mTOR, P70S6K and 4EBP1 was significantly increased after treatment with Fed compared with Fasted ex vivo human serum (P < 0.05). Here, we developed and optimized the conditions for culture of C2C12 skeletal muscle cells, measurement of MPS and signalling in medium conditioned by ex vivo human serum. Furthermore, the functionality of the model was demonstrated by comparison of the response to medium conditioned by Fasted and Fed ex vivo human serum.

The Effect of Whey Protein Supplementation on the Temporal Recovery of Muscle Function Following Resistance Training: A Systematic Review and Meta-Analysis.

Whey protein (WP) is a widely consumed nutritional supplement, known to enhance strength and muscle mass during resistance training (RT) regimens. Muscle protein anabolism is acutely elevated following RT, which is further enhanced by WP. As a result, there is reason to suggest that WP supplementation may be an effective nutritional strategy for restoring the acute loss of contractile function that occurs following strenuous RT. This systematic review and meta-analysis provides a synthesis of the literature to date, investigating the effect of WP supplementation on the recovery of contractile function in young, healthy adults. Eight studies, containing 13 randomised control trials (RCTs) were included in this review and meta-analysis, from which individual standardised effect sizes (ESs) were calculated, and a temporal overall ES was determined using a random-effects model. Whilst only half of the individual studies reported beneficial effects for WP, the high-quality evidence taken from the 13 RCTs was meta-analysed, yielding overall positive small to medium effects for WP from < 24 to 96 h (ES range = 0.4 to 0.7), for the temporal restoration of contractile function compared to the control treatment. Whilst the effects for WP were shown to be consistent over time, these results are limited to 13 RCTs, principally supporting the requirement for further comprehensive research in this area.

Dynamic measures of skeletal muscle dialysate and plasma amino acid concentration in response to exercise and nutrient ingestion in healthy adult males.

Nutrient stimulation of muscle protein synthesis (MPS) is regulated by the change in extracellular essential amino acid (EAA) concentration. In vivo microdialysis (MD) is a minimally invasive sampling technique, capable of sampling solute in the interstitial space of a target tissue. In a contralateral limb design (REST vs. EX), this study utilised in vivo MD to examine the change in skeletal muscle dialysate amino acid concentration following ingestion of whey protein isolate (WPI) and flavoured water (CON). Four male subjects undertook unilateral, concentric lower limb knee extensor resistance exercise (RE) on two occasions. After RE, an MD catheter (CMA 63) was inserted into m. vastus lateralis of the exercise and resting leg and sampled serially over 7 h. Following a 2.5 h equilibration period subjects consumed either 0.55 g/kg WPI or CON. Peak plasma EAA (2656 ± 152 µM) preceded the peak in dialysate EAA (2345 ± 164 µM) by 30 min in response to WPI ingestion; however, the post-prandial elevation in dialysate EAA extended beyond that of the plasma. This resulted in no difference in the dialysate EAA area under the curve (ΔAUC270) relative to plasma in response to WPI ingestion [220 ± 29 vs. 206 ± 7.9 mmol min/L (p = 0.700)]. A bout of unilateral lower limb RE had no effect of the subsequent dialysate amino acid concentration in response to either WPI or CON ingestion. These data represent a novel report describing the time course and magnitude of change in skeletal muscle dialysate concentration of key nutrient regulators of MPS sampled by in vivo MD, in response to nutrient ingestion with and without RE.

Optimization of an in vitro bioassay to monitor growth and formation of myotubes in real time.

The importance of growth and maintenance of skeletal muscle is vital for long term health and quality of life. Appropriate nutrition with specific bioactivities relevant to the functionalities of tissues such as skeletal muscle, can assist in maintaining and promoting adaptive responses to biological and environmental stresses which prevent muscle atrophy and promote hypertrophy. The aim of this investigation was to develop a novel in vitro cell-based electric impedance assay to study myoblast to myotube formation on the real time cell analysis (RTCA) platform (xCELLigence™, ACEA) and to validate the system by testing myotube responses to hypertrophic stimuli. C2C12 myoblasts were proliferated until 70% confluent in Dulbecco's Modified Eagles Medium (DMEM) (10% FBS) and subsequently differentiated to myotubes over 8 days in DMEM [2% horse serum (HS)]. Changes in cell behaviour and adhesion properties were monitored by measuring impedance via interdigitated microelectrodes in the base of E-16 cell culture dishes. To establish the suitability of this assay to monitor nutrient regulation of muscle hypertrophy, leucine, a known potent regulator of MPS was then supplemented to the fully formed myotubes in physiologically relevant conditions-0.20 mM, 0.40 mM, 0.6 mM, 0.8 mM and above 1.0 mM, 1.5 mM, 2.0 mM and impedance subsequently monitored. Parallel experiments highlighting alterations in myotube thickness, muscle protein synthesis (MPS) (mammalian target of rapamycin; mTOR) and differentiation (myogenin) were conducted to support RTCA bioassay findings. This in vitro bioassay can be used to monitor skeletal muscle behaviour and identify nutrient compounds with bioactivities promoting skeletal muscle hypertrophy, reducing muscle atrophy and thus inform the development of novel nutrient formulations for the maintenance of skeletal muscle.

An in vivo microdialysis characterization of the transient changes in the interstitial dialysate concentration of metabolites and cytokines in human skeletal muscle in response to insertion of a microdialysis probe.

Skeletal muscle has recently been described as an endocrine organ, capable of releasing cytokines and regulators of metabolism. Microdialysis of the interstitial space of skeletal muscle enables analysis of the release of such cytokines. The purpose of this study was to determine the transient changes in concentration of metabolites and cytokines in human skeletal muscle in a 7h period following the insertion of a microdialysis probe. In total, sixteen microdialysis catheters were inserted into the vastus lateralis of male participants (age 26.2±1.35y, height 180.8±3.89cm, mass 83.9±3.86kg, BMI 25.7±0.87kgm(-2), body fat 26.1±3.0%). Serial samples were analyzed by micro-enzymatic and multiplexed immunoassay. Muscle interstitial glucose and lactate levels remained stable throughout, amino acid concentrations stabilized after 2.5h, however, insertion of a microdialysis catheter induced a 29-fold increase in peak IL-6 (p<0.001) and 35-fold increase in peak IL-8 concentrations (p<0.001) above basal levels 6h post insertion. In contrast to stable amino acid, glucose and lactate concentrations after 2h, commonly reported markers of tissue homeostasis in in vivo microdialysis, the multi-fold increase in IL-6 and IL-8 following insertion of a microdialysis catheter is indicative of a sustained disturbance of tissue homeostasis.

Citrulline malate enhances athletic anaerobic performance and relieves muscle soreness.

The purpose of the present study was to determine the effects of a single dose of citrulline malate (CM) on the performance of flat barbell bench presses as an anaerobic exercise and in terms of decreasing muscle soreness after exercise. Forty-one men performed 2 consecutive pectoral training session protocols (16 sets). The study was performed as a randomized, double-blind, 2-period crossover design. Eight grams of CM was used in 1 of the 2 training sessions, and a placebo was used in the other. The subjects' resistance was tested using the repetitions to fatigue test, at 80% of their predetermined 1 repetition maximum (RM), in the 8 sets of flat barbell bench presses during the pectoral training session (S1-4 and S1'-4'). The p-value was 0.05. The number of repetitions showed a significant increase from placebo treatment to CM treatment from the third set evaluated (p <0.0001). This increase was positively correlated with the number of sets, achieving 52.92% more repetitions and the 100% of response in the last set (S4'). A significant decrease of 40% in muscle soreness at 24 hours and 48 hours after the pectoral training session and a higher percentage response than 90% was achieved with CM supplementation. The only side effect reported was a feeling of stomach discomfort in 14.63% of the subjects. We conclude that the use of CM might be useful to increase athletic performance in high-intensity anaerobic exercises with short rest times and to relieve postexercise muscle soreness. Thus, athletes undergoing intensive preparation involving a high level of training or in competitive events might profit from CM.