No differential effects of divergent isocaloric supplements on signaling for muscle protein turnover during recovery from muscle-damaging eccentric exercise

Unaccustomed high-intensity eccentric exercise (ECC) can provoke muscle damage including several days of muscle force loss. Post-exercise dietary supplementation may provide a strategy to accelerate rate of force regain by affecting mechanisms related to muscle protein turnover. The aim of the current study was to investigate if protein signaling mechanisms involved in muscle protein turnover would be differentially affected by supplementation with either whey protein hydrolysate and carbohydrate (WPH+CHO) versus isocaloric carbohydrate (CHO) after muscle-damaging ECC. Twenty-four young healthy participants received either WPH+CHO (n = 12) or CHO supplements (n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to, at 3 h and at 24, 48, 96 and/or 168 h post-exercise, muscle strength, muscle soreness, and Akt-mTOR and FOXO signaling proteins, were measured in an ECC exercising leg and in the contralateral non-exercise control leg (CON). After ECC, muscle force decreased by 23–27 % at 24 h post-exercise, which was followed by gradual, although not full recovery at 168 h post-exercise, with no differences between supplement groups. Phosphorylation of mTOR, p70S6K and rpS6 increased and phosphorylation of FOXO1 and FOXO3 decreased in the ECC leg, with no differences between supplement groups. Phosphorylation changes were also observed for rpS6, FOXO1 and FOXO3a in the CON leg, suggesting occurrence of remote tissue effects. In conclusion, divergent dietary supplementation types did not produce differences in signaling for muscle turnover during recovery from muscle-damaging exercise.     

Sepsis-induced changes in amino acid transporters and leucine signaling via mTOR in skeletal muscle

The present study tested the hypothesis that sepsis-induced leucine (Leu) resistance in skeletal muscle is associated with a down-regulation of amino acid transporters important in regulating Leu flux or an impairment in the formation of the Leu-sensitive mTOR–Ragulator complex. Sepsis in adult male rats decreased basal protein synthesis in gastrocnemius, associated with a reduction in mTOR activation as indicated by decreased 4E-BP1 and S6K1 phosphorylation. The ability of oral Leu to increase protein synthesis and mTOR kinase after 1 h was largely prevented in sepsis. Sepsis increased CAT1, LAT2 and SNAT2 mRNA content two- to fourfold, but only the protein content for CAT1 (20 % decrease) differed significantly. Conversely, sepsis decreased the proton-assisted amino acid transporter (PAT)-2 mRNA by 60 %, but without a coordinate change in PAT2 protein. There was no sepsis or Leu effect on the protein content for RagA-D, LAMTOR-1 and -2, raptor, Rheb or mTOR in muscle. The binding of mTOR, PRAS40 and RagC to raptor did not differ for control and septic muscle in the basal condition; however, the Leu-induced decrease in PRAS40·raptor and increase in RagC·raptor seen in control muscle was absent in sepsis. The intracellular Leu concentration was increased in septic muscle, compared to basal control conditions, and oral Leu further increased the intracellular Leu concentration similarly in both control and septic rats. Hence, while alterations in select amino acid transporters are not associated with development of sepsis-induced Leu resistance, the Leu-stimulated binding of raptor with RagC and the recruitment of mTOR/raptor to the endosome-lysosomal compartment may partially explain the inability of Leu to fully activate mTOR and muscle protein synthesis.     

Arginine protects muscle cells from wasting in vitro in an mTORC1-dependent and NO-independent manner

Amino acids are potent regulators of muscle protein synthesis and breakdown and have received considerable attention for the treatment of muscle wasting conditions. Arginine is critically involved in numerous physiological functions including providing substrate for the production of creatine, urea and nitric oxide (NO) and in the synthesis of new proteins. However, little is known about the direct effects of arginine on skeletal muscle protein synthesis during catabolic conditions. The aims of this study were to determine whether exogenous arginine could protect skeletal muscle cells from wasting directly and whether this effect was dependent on production of NO and/or activation of the rapamycin-sensitive mechanistic target of rapamycin complex 1 (mTORC1) signalling pathway. To explore these aims, we deprived mature C2C12 myotubes from nutrients and growth factors by incubating them in HEPES buffered saline with arginine or equimolar concentrations of alanine (control). Our results show that arginine: increased the ratio of phosphorylated to total mTOR (146 %), S6 (40 %) and 4EBP1 (69 %); increased protein synthesis (69 %) during the first hour of treatment; and increased myotube diameter by ~15 %. Experiments using the NO synthase inhibitor l-NG-Nitroarginine Methyl Ester showed a NO-independent protection from muscle wasting. On the other hand, the mTORC1 inhibitor rapamycin prevented increases in phosphorylated S6, protein synthesis and myotube diameter. The activation of mTORC1 and protein synthesis by arginine was not associated with changes in the phosphorylation status of Akt, but rather increased the expression of the amino acid-sensitive type III PI3-kinase Vps34 signalling protein. These data support a direct role for arginine in the regulation of mTORC1 in skeletal muscle.     

A prepared anti-MSTN polyclonal antibody reverses insulin resistance of diet-induced obese rats via regulation of PI3K/Akt/mTOR&FoxO1 signal pathways

Suppression of myostatin (MSTN) is associated with skeletal muscle atrophy and insulin resistance. However, the mechanisms by which MSTN regulates insulin resistance are not well known. We have explored the signaling pathways through which MSTN regulates insulin resistance in diet-induced obese rats using a polyclonal antibody for MSTN. The anti-MSTN polyclonal antibody significantly improved insulin resistance and whole-body insulin sensitivity, decreased MSTN protein expression in muscle samples by 39 % in diet-induced obese rats. Furthermore, the anti-MSTN polyclonal antibody significantly enhanced PI3K activity (140 %), Akt phosphorylation (86 %), GLUT4 protein expression (23 %), the phosphorylation of mTOR (21 %), and inhibited the phosphorylation of FoxO1 (57 %), but did not affect the phosphorylation of GSK-3β. Thus, suppression of MSTN by the anti-MSTN polyclonal antibody reverses insulin resistance of diet-induced obesity via MSTN/PI3K/Akt/mTOR and MSTN/PI3K/Akt/FoxO1 signaling pathways.     

Whey protein supplementation accelerates satellite cell proliferation during recovery from eccentric exercise

Human skeletal muscle satellite cells (SCs) are essential for muscle regeneration and remodeling processes in healthy and clinical conditions involving muscle breakdown. However, the potential influence of protein supplementation on post-exercise SC regulation in human skeletal muscle has not been well investigated. In a comparative human study, we investigated the effect of hydrolyzed whey protein supplementation following eccentric exercise on fiber type-specific SC accumulation. Twenty-four young healthy subjects received either hydrolyzed whey protein + carbohydrate (whey, n = 12) or iso-caloric carbohydrate (placebo, n = 12) during post-exercise recovery from 150 maximal unilateral eccentric contractions. Prior to and 24, 48 and 168 h post-exercise, muscle biopsies were obtained from the exercise leg and analyzed for fiber type-specific SC content. Maximal voluntary contraction (MVC) and serum creatine kinase (CK) were evaluated as indices of recovery from muscle damage. In type II fiber-associated SCs, the whey group increased SCs/fiber from 0.05 [0.02; 0.07] to 0.09 [0.06; 0.12] (p < 0.05) and 0.11 [0.06; 0.16] (p < 0.001) at 24 and 48 h, respectively, and exhibited a difference from the placebo group (p < 0.05) at 48 h. The whey group increased SCs/myonuclei from 4?% [2; 5] to 10?% [4; 16] (p?p < 0.001) and muscle soreness and CK increased (p < 0.001), irrespective of supplementation. In conclusion, whey protein supplementation may accelerate SC proliferation as part of the regeneration or remodeling process after high-intensity eccentric exercise.     

PAS Kinase Is a Nutrient and Energy Sensor in Hypothalamic Areas Required for the Normal Function of AMPK and mTOR/S6K1

The complications caused by overweight, obesity and type 2 diabetes are one of the main problems that increase morbidity and mortality in developed countries. Hypothalamic metabolic sensors play an important role in the control of feeding and energy homeostasis. PAS kinase (PASK) is a nutrient sensor proposed as a regulator of glucose metabolism and cellular energy. The role of PASK might be similar to other known metabolic sensors, such as AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR). PASK-deficient mice resist diet-induced obesity. We have recently reported that AMPK and mTOR/S6K1 pathways are regulated in the ventromedial and lateral hypothalamus in response to nutritional states, being modulated by anorexigenic glucagon-like peptide-1 (GLP-1)/exendin-4 in lean and obese rats. We identified PASK in hypothalamic areas, and its expression was regulated under fasting/re-feeding conditions and modulated by exendin-4. Furthermore, PASK-deficient mice have an impaired activation response of AMPK and mTOR/S6K1 pathways. Thus, hypothalamic AMPK and S6K1 were highly activated under fasted/re-fed conditions. Additionally, in this study, we have observed that the exendin-4 regulatory effect in the activity of metabolic sensors was lost in PASK-deficient mice, and the anorexigenic properties of exendin-4 were significantly reduced, suggesting that PASK could be a mediator in the GLP-1 signalling pathway. Our data indicated that the PASK function could be critical for preserving the nutrient effect on AMPK and mTOR/S6K1 pathways and maintain the regulatory role of exendin-4 in food intake. Some of the antidiabetogenic effects of exendin-4 might be modulated through these processes.     

Role of different aberrant cell signalling pathways prevalent in acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is one of the major forms of leukemia that affects mostly adolescent individuals. The main cause of the development of ALL is not known though several important signal transduction pathways have been reported with functional abnormality in all the cases. Crucial signalling pathways reported in ALL include PI3K/Akt, Notch, Wnt, mTOR, JaK/Stat, etc. Over the past several decades important progress has been made in the management of ALL, however, relapses and post therapy survival ratio has not improved much. This brings the need for understanding the biology and mechanism involved in ALL occurrences and find new molecular targets for better treatment options and risk-adapted therapies to improve the outcome of ALL patients.     

The role of the MEK/ERK pathway in regulation of HDACI-induced senescence of transformed rat embryo fibroblasts

A key regulator of cellular senescence, mTORC1 complex, is a target of many signaling cascades, including Ras/Raf/MEK/ERK cascade. In this paper, we investigated the role of the MEK/ERK branch of this cascade in the process of cellular senescence induced by sodium butyrate (NaBut), a histone deacetylase inhibitor (HDACI), in transformed rat-embryo fibroblasts. Suppression of MEK/ERK activity by inhibitor PD0325901 did not prevent activation of mTORC1 complex induced by NaBut treatment. Inhibition of MEK/ERK increased mTORC1 activity and activated mTORC2 complex. Activation of mTOR-containing complexes was accompanied by reorganization of the actin cytoskeleton (formation of actin stress fibers) and the appearance of cellular senescence markers. In contrast to NaBut-induced senescence, no protein accumulation was observed, probably due to increased activity of the degradation processes. Furthermore, senescence induction under suppression of MEK/ERK drastically decreased the cell viability, Thus, NaBut-induced senescence upon suppressed activity of the MEK/ERK branch of MAP kinase cascade has a more pronounced tumor-suppressing effect that is manifested by activation of both mTOR complexes, reorganization of the actin cytoskeleton and protein degradation.     

EGFR-AKT-mTOR activation mediates epiregulin-induced pleiotropic functions in cultured osteoblasts

Epidermal growth factor (EGF) receptor (EGFR) emerges as an essential molecule for the regulating of osteoblast cellular functions. In the current study, we explored the effect of epiregulin, a new EGFR ligand, on osteoblast functions in vitro, and studied the underlying mechanisms. We found that epiregulin-induced EGFR activation in both primary osteoblasts and osteoblast-like MC3T3-E1 cells. Meanwhile, epiregulin activated AKT-mammalian target of rapamycin (mTOR) and Erk-mitogen-activated protein kinase (MAPK) signalings in cultured osteoblasts, which were blocked by EGFR inhibitor AG1478 or monoclonal antibody against EGFR (anti-EGFR). Further, in primary and MC3T3-E1 osteoblasts, epiregulin promoted cell proliferation and increased alkaline phosphatase activity, while inhibiting dexamethasone (Dex)-induced cell death. Such effects by epiregulin were largely inhibited by AG1478 or anti-EGFR. Notably, AKT-mTOR inhibitors, but not Erk inhibitors, alleviated epiregulin-induced above pleiotropic functions in osteoblasts. Meanwhile, siRNA depletion of Sin1, a key component of mTOR complex 2 (mTORC2), also suppressed epiregulin-exerted effects in MC3T3-E1 cells. Together, these results suggest that epiregulin-induced pleiotropic functions in cultured osteoblasts are mediated through EGFR-AKT-mTOR signalings.     

Human exercise-mediated skeletal muscle hypertrophy is an intrinsic process

Muscle cells (fibres) are post-mitotic and thus undergo changes in phenotype by modifying their existing structure. Hypertrophy is a hallmark change that occurs in response to increased loading and can be achieved in humans through repeated bouts of resistance exercise (i.e., training). In resistance exercise, contractions are initiated by neural drive leading to immediate perturbations such as calcium influx, cross-bridge cycling and tension/stress on the cytoskeleton, sarcolemma and extracellular matrix, as well as more delayed cellular events such as the production/release of potential local growth factors (e.g., IGF-1). Resistance exercise can also elevate the systemic concentration of certain hormones (growth hormone, testosterone, IGF-1) that are hypothesized to drive hypertrophy. However, while these hormones are clearly anabolic during childhood and puberty, or when given at supraphysiological exogenous doses, the transient post-exercise elevations in hormone concentration are of little consequence to the either the acute protein synthetic response or to a hypertrophic phenotype after resistance training. Thus, the acute post-exercise increases in systemic hormones are in no way a proxy marker for anabolism since they do not underpin the capacity of the muscle to hypertrophy in any measurable way. In contrast, the acute activation of intrinsically located signalling proteins such as p70^S6K and the acute elevation of muscle protein synthesis are more reflective of the potential to increase in muscle mass with resistance training. Ultimately, local mechanisms are activated by the stress imposed by muscle loading and prime the muscle for protein accretion. Membrane-derived molecules and tension-sensing pathways are two intrinsic mechanisms implicated in upregulating the synthesis and incorporation of muscle proteins into the myofibre in response to mechanical stress derived from loaded contractions.     

Post-exercise carbohydrate plus whey protein hydrolysates supplementation increases skeletal muscle glycogen level in rats

Recent studies showed that a combination of carbohydrate and protein was more effective than carbohydrate alone for replenishing muscle glycogen after exercise. However, it remains to be unclear whether the source or degree of hydrolysis of dietary protein influences post-exercise glycogen accumulation. The aim of this study was to compare the effect of dietary protein type on glycogen levels in the post-exercise phase, and to investigate the effects of post-exercise carbohydrate and protein supplementation on phosphorylated enzymes of Akt/PKB and atypical PKCs. Male Sprague-Dawley rats, trained for 3 days, swam with a 2% load of body weight for 4 h to deplete skeletal muscle glycogen. Immediately after the glycogen-depleting exercise, one group was killed, whereas the other groups were given either glucose or glucose plus protein (whey protein, whey protein hydrolysates (WPH), casein hydrolysates or branched-chain amino acid (BCAA) solutions. After 2 h, the rats were killed, and the triceps muscles quickly excised. WPH caused significant increases in skeletal muscle glycogen level (5.01 ± 0.24 mg/g), compared with whey protein (4.23 ± 0.24 mg/g), BCAA (3.92 ± 0.18 mg/g) or casein hydrolysates (2.73 ± 0.22 mg/g). Post-exercise ingestion of glucose plus WPH significantly increased both phosphorylated Akt/PKB (131%) and phosphorylated PKCζ (154%) levels compared with glucose only. There was a significant positive correlation between skeletal muscle glycogen content and phosphorylated Akt/PKB (r = 0.674, P < 0.001) and PKCζ (r = 0.481, P = 0.017). Post-exercise supplementation with carbohydrate and WPH increases skeletal muscle glycogen recovery by activating key enzymes such as Akt/PKB and atypical PKCs.     

Effects of carbohydrate supplementation on force output and time to exhaustion during static leg contractions superimposed with electromyostimulation

The purpose of this study was to investigate the effects of carbohydrate ingestion on force output and time to exhaustion using single leg static contractions superimposed with brief periods of electromyostimulation. Six trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second static contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40-second rest until failure occurred. Importantly, the force output during quadriceps maximal voluntary contraction strength with superimposed electromyostimulation was measured in the beginning and every 5 minutes during the last 3 seconds of static contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for blood lactate. Our results indicate that time to exhaustion (PL = 16.0 ± 8.1 minutes; CHO = 29.0 ± 13.1 minutes) and force output (PL = 3,638.7 ± 524.5 N; CHO = 5,540.1 ± 726.1 N) were significantly higher (p < 0.05) in CHO compared with that in PL. Data suggest that carbohydrate ingestion before and during static muscle contractions can increase force output and increase time to exhaustion. Therefore, our data suggest that carbohydrate supplementation before and during resistance exercise might help increase the training volume of athletes.     

The effect of carbohydrate ingestion on plasma interleukin-6, hepcidin and iron concentrations following prolonged exercise

The aim of our study was twofold, firstly to examine the relationship between plasma concentrations of IL-6, hepcidin and iron following prolonged exercise and secondly, to assess the effect of carbohydrate ingestion on circulating hepcidin concentration post-exercise. The study was a randomised double-blind cross-over design, with participants consuming either a carbohydrate (CHO) or an isovolumetric placebo drink throughout the trial. Nine healthy, trained males completed a treadmill run at 60% vVO(2max) for 120 min followed by a 5 km time trial. Plasma concentrations of both IL-6 and hepcidin significantly increased post-exercise following both trials (p<.05) and returned to baseline by 24 h post (p>.05). A positive correlation between hepcidin and IL-6 was demonstrated immediately following exercise during PLA while there was a trend for a moderate correlation during CHO (PLA trial rho=0.81, p<0.001; CHO trial rho=0.36, p=0.07). Plasma iron was unaffected immediately post-exercise but significantly reduced by 24 h post-exercise compared to baseline. CHO ingestion significantly reduced post-exercise IL-6 (p<.05) but this had no effect on plasma hepcidin or iron concentration. Our data demonstrate CHO supplementation does not alter the rapid hepcidin response associated with exercise and does not prevent a subsequent fall in plasma iron concentration. This finding adds further support to the theory that an exercise-induced, up-regulation of hepcidin activity is a mechanism causing iron deficiency in endurance athletes.     

Modulation of inducible nitric oxide synthase (iNOS) expression and cardiovascular responses during static exercise following iNOS antagonism within the ventrolateral medulla

Previous reports indicate that inducible nitric oxide synthase (iNOS) blockade within the rostral ventrolateral medulla (RVLM) and caudal ventrolateral medulla (CVLM) differentially modulated cardiovascular responses, medullary glutamate, and GABA concentrations during static skeletal muscle contraction. In the current study, we determined the role of iNOS antagonism within the RVLM and CVLM on cardiovascular responses and iNOS protein expression during the exercise pressor reflex in anesthetized rats. Following 120 min of bilateral microdialysis of a selective iNOS antagonist, aminoguanidine (AGN; 10 µM), into the RVLM, the pressor responses were attenuated by 72 % and changes in heart rate were reduced by 38 % during a static muscle contraction. Furthermore, western blot analysis of iNOS protein abundance within the RVLM revealed a significant attenuation when compared to control animals. In contrast, bilateral administration of AGN (10 µM) into the CVLM augmented the increases in mean arterial pressure by 60 % and potentiated changes in heart rate by 61 % during muscle contractions, but did not alter expression of the iNOS protein within the CVLM. These results demonstrate that iNOS protein expression within the ventrolateral medulla is differentially regulated by iNOS blockade that may, in part, contribute to the modulation of cardiovascular responses during static exercise.     

Consumption of an oral carbohydrate-protein gel improves cycling endurance and prevents postexercise muscle damage

Investigators have reported improved endurance performance and attenuated post-exercise muscle damage with carbohydrate-protein beverages (CHO+P) versus carbohydrate-only beverages (CHO). However, these benefits have been demonstrated only when CHO+P was administered in beverage-form, and exclusively in male subjects. Thus, the purposes of this study were to determine if an oral CHO+P gel improved endurance performance and post-exercise muscle damage compared to a CHO gel, and determine if responses were similar between genders. Thirteen cyclists (8 men, 5 women; VO(2)peak = 57.9 +/- 7.0 ml x kg(-1) x min(-1)) completed two timed cycle-trials to volitional exhaustion at 75% of VO(2)peak. At 15-minute intervals throughout these rides, subjects received CHO or CHO+P gels, which were matched for carbohydrate content (CHO = 0.15 g CHO x kg BW(-1); CHO+P = 0.15 g CHO + 0.038 g protein x kg BW(-1)). Trials were performed using a randomly counterbalanced, double-blind design. Subjects rode 13% longer (p < 0.05) when utilizing the CHO+P gel (116.6 +/- 28.5 minutes) versus the CHO gel (102.8 +/- 25.0 minutes). In addition, men (101.8 +/- 24.6; 114.8 +/- 26.2) and women (104.4 +/- 28.6; 119.6 +/- 34.9) responded similarly to the CHO and CHO+P trials, with no significant treatment-by-gender effect. Postexercise creatine kinease (CK) was not significantly different between treatments. However, CK increased significantly following exercise in the CHO trial (183 +/- 116; 267 +/- 214 U x L(-1)), but not the CHO+P trial (180 +/- 133; 222 +/- 141 U x L(-1)). Therefore, to prolong endurance performance and prevent increases in muscle damage, it is recommended that male and female cyclists consume CHO+P gels rather than CHO gels during and immediately following exercise.     

Crystal structures of the S6K1 kinase domain in complexes with inhibitors

Ribosomal protein S6 kinase 1 (S6K1) is a serine/threonine protein kinase that plays an important role in the PIK3/mTOR signaling pathway, and is implicated in diseases including diabetes, obesity, and cancer. The crystal structures of the S6K1 kinase domain in complexes with staurosporine and the S6K1-specific inhibitor PF-4708671 have been reported. In the present study, five compounds (F108, F109, F176, F177, and F179) were newly identified by in silico screening of a chemical library and kinase assay. The crystal structures of the five inhibitors in complexes with the S6K1 kinase domain were determined at resolutions between 1.85 and 2.10 Å. All of the inhibitors bound to the ATP binding site, lying along the P-loop, while the activation loop stayed in the inactive form. Compound F179, with a carbonyl group in the middle of the molecule, altered the αC helix conformation by interacting with the invariant Lys123. Compounds F176 and F177 bound slightly distant from the hinge region, and their sulfoamide groups formed polar interactions with the protein. The structural features required for the specific binding of inhibitors are discussed.     

The effects of a glycogen loading regimen on acid-base status and blood lactate concentration before and after a fixed period of high intensity exercise in man

Six healthy male subjects exercised after an overnight fast for a fixed 3 min period at a workload equivalent to 100% of their maximal oxygen uptake ( ) on 3 separate occasions. The first test took place after subjects had consumed a mixed diet (43±3% carbohydrate (CHO), 41±5% fat and 16±3% protein) for 3 days, and was followed 2 h later by prolonged cycling to exhaustion at 77±3% to deplete muscle glycogen stores. Following this, subjects consumed a low CHO diet (4±1% CHO, 63±5% fat and 33±6% protein) for the remainder of the day and for the subsequent 2 days; on the morning of the next day a second high intensity test took place. Finally subjects followed a 3 day high CHO diet (73±7% CHO, 17±6% fat and 10±1% protein) before their last test. Acid-base status and selected metabolites were measured on arterialised-venous blood at rest prior to exercise and at intervals for 15 min following exercise. Prior to exercise, plasma pH and blood lactate concentration were higher (p<0.05) after the high CHO diet when compared with the low CHO diet. Pre-exercise plasma bicarbonate, blood PCO₂ and blood base excess were all higher after the high (p<0.001,p<0.01,p<0.01 respectively) and normal (p<0.05,p<0.05,p<0.05 respectively) CHO diets when compared with the low CHO diet. During the post-exercise period there were no differences in plasma pH or blood base excess between the three experimental situations; plasma bicarbonate was higher (p<0.05) at 2 min post-exercise after the high CHO diet when compared with the low CHO diet; blood PCO₂ was higher throughout the post-exercise period after the high CHO diet when compared with the low CHO diet and at 2 min post-exercise was higher after the normal CHO diet than after the low CHO diet (p<0.5). The post-exercise blood lactate concentration after the high CHO diet was at all times higher than the corresponding values recorded after the normal CHO diet and until 15 min post-exercise was significantly higher than the values recorded after the low CHO diet. The present experiment further substantiates the view that a pattern of dietary and exercise manipulation can significantly influence the acid-base status of the blood and by doing so may influence high intensity exercise performance.