Similar performance after intake of carbohydrate plus whey protein and carbohydrate only in the early phase after non-exhaustive cycling.

AIM: The aim of the present study was to compare performance 5 h after a 90-min endurance training session when either carbohydrate only or carbohydrate with added whey hydrolysate or whey isolate was ingested during the first 2 h of the recovery period. METHODS: Thirteen highly trained competitive male cyclists completed three exercise and diet interventions (double-blinded, randomized, crossover design) separated by 1 week. The 90-min morning session (EX1) included a 60 min time-trial (TT60 ). Immediately and 1 h after exercise, participants ingested either (1) 1.2 g carbohydrate∙kg-1 ∙h-1 (CHO), (2) 0.8 g carbohydrate∙kg-1 ∙h-1 + 0.4 g isolate whey protein∙kg-1 ∙h-1 (ISO) or (3) 0.8 g carbohydrate∙kg-1 ∙h-1 + 0.4 g hydrolysate whey protein∙kg-1 ∙h-1 (HYD). Additional intakes were identical between interventions. After 5 h of recovery, participants completed a time-trial performance (TTP ) during which a specific amount of work was performed. Blood and urine were collected throughout the day. RESULTS: TTP did not differ significantly between dietary interventions (CHO: 43:54 ± 1:36, ISO: 46:55 ± 2:32, HYD: 44:31 ± 2:01 min). Nitrogen balance during CHO was lower than ISO (p < 0.0001) and HYD (p < 0.0001), with no difference between ISO and HYD (p = 0.317). In recovery, the area under the curve for blood glucose was higher in CHO compared to ISO and HYD. HR, VO2 , RER, glucose, and lactate during EX2 were similar between interventions. CONCLUSION: Performance did not differ after 5 h of recovery whether carbohydrate only or isocaloric carbohydrate plus protein was ingested during the first 2 h. Correspondingly, participants were not in negative nitrogen balance in any dietary intervention.

Exhaustive Exercise and Post-exercise Protein Plus Carbohydrate Supplementation Affect Plasma and Urine Concentrations of Sulfur Amino Acids, the Ratio of Methionine to Homocysteine and Glutathione in Elite Male Cyclists.

Plasma and tissue sulfur amino acid (SAA) availability are crucial for intracellular methylation reactions and cellular antioxidant defense, which are important processes during exercise and in recovery. In this randomized, controlled crossover trial among eight elite male cyclists, we explored the effect of exhaustive exercise and post-exercise supplementation with carbohydrates and protein (CHO+PROT) vs. carbohydrates (CHO) on plasma and urine SAAs, a potential new marker of methylation capacity (methionine/total homocysteine ratio [Met/tHcy]) and related metabolites. The purpose of the study was to further explore the role of SAAs in exercise and recovery. Athletes cycled to exhaustion and consumed supplements immediately after and in 30 min intervals for 120 min post-exercise. After ~18 h recovery, performance was tested in a time trial in which the CHO+PROT group cycled 8.5% faster compared to the CHO group (41:53 ± 1:51 vs. 45:26 ± 1:32 min, p < 0.05). Plasma methionine decreased by ~23% during exhaustive exercise. Two h post-exercise, further decline in methionine had occured by ~55% in the CHO group vs. ~33% in the CHO+PROT group (pgroup × time < 0.001). The Met/tHcy ratio decreased by ~33% during exhaustive exercise, and by ~54% in the CHO group vs. ~27% in the CHO+PROT group (pgroup × time < 0.001) post-exercise. Plasma cystathionine increased by ~72% in the CHO group and ~282% in the CHO+PROT group post-exercise (pgroup × time < 0.001). Plasma total cysteine, taurine and total glutathione increased by 12% (p = 0.03), 85% (p < 0.001) and 17% (p = 0.02), respectively during exhaustive exercise. Using publicly available transcriptomic data, we report upregulated transcript levels of skeletal muscle SLC7A5 (log2 fold-change: 0.45, FDR:1.8e-07) and MAT2A (log2 fold-change: 0.38, FDR: 3.4e-0.7) after acute exercise. Our results show that exercise acutely lowers plasma methionine and the Met/tHcy ratio. This response was attenuated in the CHO+PROT compared to the CHO group in the early recovery phase potentially affecting methylation capacity and contributing to improved recovery.

Inorganic Nitrate Supplementation for Cardiovascular Health.

Nitric oxide (NO) is continually produced by the enzyme nitric oxide synthase (NOS) and is essential to the control and effectiveness of the cardiovascular system. However, there is a substantial reduction in NOS activity with aging that can lead to the development of hypertension and other cardiovascular complications. Fortunately, NO can also be produced by the sequential reduction of inorganic nitrate to nitrite and then to NO. Nitric oxide from inorganic nitrate supplementation has been found to have the same cardioprotective benefits of NO produced by NOS. Moreover, it can effectively compensate for declining NOS activity due to aging or NOS inhibition by oxidative stress, hypoxia, or other factors. This review covers some of the major cardiovascular regulatory actions of NO and presents evidence that NO from inorganic nitrate supplementation can provide (1) compensation when NOS activity is inadequate, and (2) cardioprotective benefits beyond that provided by a healthy NOS system. In addition, it discusses how to obtain a safe and efficacious range of inorganic nitrate.

Chocolate Milk versus carbohydrate supplements in adolescent athletes: a field based study.

PURPOSE: The purpose of this study is to translate laboratory-based research on beverage-based supplements to a naturalistic, field setting in adolescent athletes. To this end, we tested the effects of two commercially-available drinks on strength in a field-based setting with both male and female high school athletes completing a summer training program. METHODS: One hundred and three high school athletes completed the study (M age = 15.3, SD = 1.2; 70.9% male; 37.9% Afr. Amer.). Measures included a composite strength score (bench press + squat). Participants completed 1 week of pre- and post-testing, and 4 days per week of strength and conditioning training for 5 weeks. Participants were randomly-assigned to receive either CM or CHO immediately post-exercise. RESULTS: A 2 (group) × 2 (time) repeated measures ANOVA showed there was a significant main effect on time for increase in the composite strength score (p = .002, ŋp2 = .18). There was a significant interaction of composite strength score between groups, (p = .04, ŋp2 = .08). The CM group (12.3% increase) had significantly greater improvements in composite strength from pre- to post-test than CHO (2.7% increase). There were no differences in these results based on demographic variables. CONCLUSION: This is the first study comparing the impact of CM and CHO on athletic outcomes in an adolescent population in a field-based environment. CM had a more positive effect on strength development and should be considered an appropriate post-exercise recovery supplement for adolescents. Future research will benefit from longer study durations with larger numbers of participants.

Intake of Protein Plus Carbohydrate during the First Two Hours after Exhaustive Cycling Improves Performance the following Day.

Intake of protein immediately after exercise stimulates protein synthesis but improved recovery of performance is not consistently observed. The primary aim of the present study was to compare performance 18 h after exhaustive cycling in a randomized diet-controlled study (175 kJ·kg(-1) during 18 h) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg(-1) during 18 h) on performance when protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg(-1)·h(-1) (CHO), 0.8 g carbohydrate + 0.4 g protein·kg(-1)·h(-1) (CHO+PRO) or placebo without energy (PLA). Intake of CHO+PROT increased plasma glucose, insulin, and branch chained amino acids, whereas CHO only increased glucose and insulin. Eighteen hours later, subjects performed another TTE at 237±6 Watt. TTE was increased after intake of CHO+PROT compared to CHO (63.5±4.4 vs 49.8±5.4 min; p<0.05). PLA reduced TTE to 42.8±5.1 min (p<0.05 vs CHO). Nitrogen balance was positive in CHO+PROT, and negative in CHO and PLA. In conclusion, performance was higher 18 h after exhaustive cycling with intake of CHO+PROT compared to an isocaloric amount of carbohydrate during the first 2 h post exercise. Intake of a similar amount of protein but less carbohydrate during the 18 h recovery period reduced performance.

L-Alanylglutamine inhibits signaling proteins that activate protein degradation, but does not affect proteins that activate protein synthesis after an acute resistance exercise.

Sustamine™ (SUS) is a dipeptide composed of alanine and glutamine (AlaGln). Glutamine has been suggested to increase muscle protein accretion; however, the underlying molecular mechanisms of glutamine on muscle protein metabolism following resistance exercise have not been fully addressed. In the present study, 2-month-old rats climbed a ladder 10 times with a weight equal to 75 % of their body mass attached at the tail. Rats were then orally administered one of four solutions: placebo (PLA-glycine = 0.52 g/kg), whey protein (WP = 0.4 g/kg), low dose of SUS (LSUS = 0.1 g/kg), or high dose of SUS (HSUS = 0.5 g/kg). An additional group of sedentary (SED) rats was intubated with glycine (0.52 g/kg) at the same time as the ladder-climbing rats. Blood samples were collected immediately after exercise and at either 20 or 40 min after recovery. The flexor hallucis longus (FHL), a muscle used for climbing, was excised at 20 or 40 min post exercise and analyzed for proteins regulating protein synthesis and degradation. All supplements elevated the phosphorylation of FOXO3A above SED at 20 min post exercise, but only the SUS supplements significantly reduced the phosphorylation of AMPK and NF-kB p65. SUS supplements had no effect on mTOR signaling, but WP supplementation yielded a greater phosphorylation of mTOR, p70S6k, and rpS6 compared with PLA at 20 min post exercise. However, by 40 min post exercise, phosphorylation of mTOR and rpS6 in PLA had risen to levels not different than WP. These results suggest that SUS blocks the activation of intracellular signals for MPB, whereas WP accelerates mRNA translation.

Improved inflammatory balance of human skeletal muscle during exercise after supplementations of the ginseng-based steroid Rg1.

UNLABELLED: The purpose of the study was to determine the effect of ginseng-based steroid Rg1 on TNF-alpha and IL-10 gene expression in human skeletal muscle against exercise challenge, as well as on its ergogenic outcomes. Randomized double-blind placebo-controlled crossover trials were performed, separated by a 4-week washout. Healthy young men were randomized into two groups and received capsule containing either 5 mg of Rg1 or Placebo one night and one hour before exercise. Muscle biopsies were conducted at baseline, immediately and 3 h after a standardized 60-min cycle ergometer exercise. While treatment differences in glycogen depletion rate of biopsied quadriceps muscle during exercise did not reach statistical significance, Rg1 supplementations enhanced post-exercise glycogen replenishment and increased citrate synthase activity in the skeletal muscle 3 h after exercise, concurrent with improved meal tolerance during recovery (P<0.05). Rg1 suppressed the exercise-induced increases in thiobarbituric acids reactive substance (TBARS) and reversed the increased TNF-alpha and decreased IL-10 mRNA of quadriceps muscle against the exercise challenge. PGC-1 alpha and GLUT4 mRNAs of exercised muscle were not affected by Rg1. Maximal aerobic capacity (VO2max) was not changed by Rg1. However, cycling time to exhaustion at 80% VO2max increased significantly by ~20% (P<0.05). CONCLUSION: Our result suggests that Rg1 is an ergogenic component of ginseng, which can minimize unwanted lipid peroxidation of exercised human skeletal muscle, and attenuate pro-inflammatory shift under exercise challenge.

The effect of an amino acid beverage on glucose response and glycogen replenishment after strenuous exercise.

PURPOSE: We previously reported that an amino acid mixture (AA) was able to lower the glucose response to an oral glucose challenge in both rats and humans. Increased glucose uptake and glycogen storage in muscle might be associated with the faster blood glucose clearance. We therefore tested the effect of two different doses of AA provided with a carbohydrate supplement on blood glucose homeostasis and muscle glycogen replenishment in human subjects after strenuous aerobic exercise. METHODS: Ten subjects received a carbohydrate (1.2 g/kg body weight, CHO), CHO/HAA (CHO + 13 g AA), or CHO/LAA (CHO + 6.5 g AA) supplement immediately and 2 h after an intense cycling bout. Muscle biopsies were performed immediately and 4 h after exercise. RESULTS: The glucose responses for CHO/HAA and CHO/LAA during recovery were significantly lower than CHO, as was the glucose area under the curve (CHO/HAA 1259.9 ± 27.7, CHO/LAA 1251.5 ± 47.7, CHO 1376.8 ± 52.9 mmol/L 4 h, p < 0.05). Glycogen storage rate was significantly lower in CHO/HAA compared with CHO, while it did not differ significantly between CHO/LAA or CHO (CHO/HAA 15.4 ± 2.0, CHO/LAA 18.1 ± 2.0, CHO 21.5 ± 1.4 µmol/g wet muscle 4 h). CHO/HAA caused a significantly higher insulin response and a greater effect on mTOR and Akt/PKB phosphorylation compared with CHO. Phosphorylation of AS160 and glycogen synthase did not differ across treatments. Likewise, there were no differences in blood lactate across treatments. CONCLUSIONS: The AA lowered the glucose response to a carbohydrate supplement after strenuous exercise. However, it was not effective in facilitating subsequent muscle glycogen storage.

Effect of acute DHEA administration on free testosterone in middle-aged and young men following high-intensity interval training.

With advancing age, plasma testosterone levels decline, with free testosterone levels declining more significantly than total testosterone. This fall is thought to underlie the development of physical and mental weakness that occurs with advancing age. In addition, vigorous exercise can also lower total and free testosterone levels with the decline greatest in physically untrained men. The purpose of the study was to evaluate the effect of oral DHEA supplementation, a testosterone precursor, on free testosterone in sedentary middle-aged men during recovery from a high-intensity interval training (HIIT) bout of exercise. A randomized, double-blind, placebo-controlled crossover study was conducted for 8 middle-aged participants (aged 49.3 ± 2.4 years) and an additional 8 young control participants (aged 21.4 ± 0.3 years). Each participant received DHEA (50 mg) and placebo on separate occasions one night (12 h) before a 5-session, 2-min cycling exercise (100% VO2max). While no significant age difference in total testosterone was found, middle-aged participants exhibited significantly lower free testosterone and greater luteinizing hormone (LH) levels than the young control group. Oral DHEA supplementation increased circulating DHEA-S and free testosterone levels well above baseline in the middle-aged group, with no significant effect on total testosterone levels. Total testosterone and DHEA-S dropped significantly until 24 h after HIIT for both age groups, while free testosterone of DHEA-supplemented middle-aged men remained unaffected. These results demonstrate acute oral DHEA supplementation can elevate free testosterone levels in middle-aged men and prevent it from declining during HIIT. Therefore, DHEA supplementation may have significant benefits related to HIIT adaptation.

Deep ocean mineral water accelerates recovery from physical fatigue.

BACKGROUND: Deep oceans have been suggested as a possible site where the origin of life occurred. Along with this theoretical lineage, experiments using components from deep ocean water to recreate life is underway. Here, we propose that if terrestrial organisms indeed evolved from deep oceans, supply of deep ocean mineral water (DOM) to humans, as a land creature, may replenish loss of molecular complexity associated with evolutionary sea-to-land migration. METHODS: We conducted a randomized, double-blind, placebo-controlled crossover human study to evaluate the effect of DOM, taken from a depth of 662 meters off the coast of Hualien, Taiwan, on time of recovery from a fatiguing exercise conducted at 30°C. RESULTS: The fatiguing exercise protocol caused a protracted reduction in aerobic power (reduced VO2max) for 48 h. However, DOM supplementation resulted in complete recovery of aerobic power within 4 h (P < 0.05). Muscle power was also elevated above placebo levels within 24 h of recovery (P < 0.05). Increased circulating creatine kinase (CK) and myoglobin, indicatives of exercise-induced muscle damage, were completely eliminated by DOM (P < 0.05) in parallel with attenuated oxidative damage (P < 0.05). CONCLUSION: Our results provide compelling evidence that DOM contains soluble elements, which can increase human recovery following an exhaustive physical challenge.

Effect of dehydroepiandrosterone administration on recovery from mix-type exercise training-induced muscle damage.

This study aimed to determine the role of DHEA-S in coping against the exercise training mixing aerobic and resistance components. During 5-day successive exercise training, 16 young male participants (19.2 ± 1.2 years) received either a placebo (flour capsule) or DHEA (100 mg/day) in a double-blinded and placebo-controlled design. Oral DHEA supplementation significantly increased circulating DHEA-S by 2.5-fold, but a protracted drop (~35 %) was observed from Day 3 during training. In the Placebo group, only a minimal DHEA-S reduction (~17 %) was observed. Changes in testosterone followed a similar pattern as DHEA-S. Muscle soreness was elevated significantly on Day 2 for both groups to a similar extent. Lower muscle soreness was observed in the DHEA-supplemented group on Day 3 and Day 6. In the Placebo group, training increased circulating creatine kinase (CK) levels by approximately ninefold, while only a threefold increase was observed in the DHEA-supplemented group. This mix-type exercise training improved glucose tolerance in both groups, while lowering the insulin response to the glucose challenge, but no difference between treatments was observed. Our results suggest that DHEA-S may play a role in protecting skeletal muscle from exercise training-induced muscle damage.

Amino acid mixture acutely improves the glucose tolerance of healthy overweight adults.

Certain amino acids have been reported to influence carbohydrate metabolism and blood glucose clearance, as well as improve the glucose tolerance in animal models. We hypothesized that an amino acid mixture consisting of isoleucine and 4 additional amino acids would improve the glucose response of healthy overweight men and women to an oral glucose tolerance test (OGTT). Twenty-two overweight healthy subjects completed 2 OGTTs after consuming 2 different test beverages. The amino acid mixture beverage (CHO/AA) consisted of 0.088 g cystine 2HCl, 0.043 g methionine, 0.086 g valine, 12.094 g isoleucine, 0.084 g leucine, and 100 g dextrose. The control beverage (CHO) consisted of 100 g dextrose only. Venous blood samples were drawn 10 minutes before the start of ingesting the drinks and 15, 30, 60, 120, and 180 minutes after the completion of the drinks. During the OGTT, the plasma glucose response for the CHO/AA treatment was significantly lower than that of the CHO treatment (P < .01), as was the plasma glucose area under the curve (CHO/AA 806 ± 31 mmol/L·3 hours vs CHO 942 ± 40 mmol/L·3 hours). Differences in plasma glucose between treatments occurred at 30, 60, 120, and 180 minutes after supplement ingestion. Plasma glucagon during the CHO/AA treatment was significantly higher than during the CHO treatment. However, there were no significant differences in plasma insulin or C-peptide responses between treatments. These results suggest that the amino acid mixture lowers the glucose response to an OGTT in healthy overweight subjects in an insulin-independent manner.

Postexercise carbohydrate-protein supplementation improves subsequent exercise performance and intracellular signaling for protein synthesis.

Postexercise carbohydrate-protein (CHO + PRO) supplementation has been proposed to improve recovery and subsequent endurance performance compared to CHO supplementation. This study compared the effects of a CHO + PRO supplement in the form of chocolate milk (CM), isocaloric CHO, and placebo (PLA) on recovery and subsequent exercise performance. Ten cyclists performed 3 trials, cycling 1.5 hours at 70% VO2max plus 10 minutes of intervals. They ingested supplements immediately postexercise and 2 hours into a 4-hour recovery. Biopsies were performed at recovery minutes 0, 45, and 240 (R0, R45, REnd). Postrecovery, subjects performed a 40-km time trial (TT). The TT time was faster in CM than in CHO and in PLA (79.43 ± 2.11 vs. 85.74 ± 3.44 and 86.92 ± 3.28 minutes, p ≤ 0.05). Muscle glycogen resynthesis was higher in CM and in CHO than in PLA (23.58 and 30.58 vs. 7.05 µmol·g⁻¹ wet weight, p ≤ 0.05). The mammalian target of rapamycin phosphorylation was greater at R45 in CM than in CHO or in PLA (174.4 ± 36.3 vs. 131.3 ± 28.1 and 73.7 ± 7.8% standard, p ≤ 0.05) and at REnd in CM than in PLA (94.5 ± 9.9 vs. 69.1 ± 3.8%, p ≤ 0.05). rpS6 phosphorylation was greater in CM than in PLA at R45 (41.0 ± 8.3 vs. 15.3 ± 2.9%, p ≤ 0.05) and REnd (16.8 ± 2.8 vs. 8.4 ± 1.9%, p ≤ 0.05). FOXO3A phosphorylation was greater at R45 in CM and in CHO than in PLA (84.7 ± 6.7 and 85.4 ± 4.7 vs. 69.2 ± 5.5%, p ≤ 0.05). These results indicate that postexercise CM supplementation can improve subsequent exercise performance and provide a greater intracellular signaling stimulus for PRO synthesis compared to CHO and placebo.

Effect of carbohydrate-protein supplementation postexercise on rat muscle glycogen synthesis and phosphorylation of proteins controlling glucose storage.

To examine whether addition of protein to a carbohydrate supplement enhances muscle glycogen synthesis, we compared the muscle glycogen concentrations of rats that had been depleted of their muscle glycogen stores with a 3-hour swim and immediately supplemented with a placebo (Con), carbohydrate (CHO), or carbohydrate plus protein supplement (C+P). Rats were given either 0.9 g carbohydrate per kilogram body mass for the CHO group or 0.9 g carbohydrate + 0.3 g protein per kilogram body mass for the C+P groups. Muscle samples of the red and white quadriceps were excised immediately, 30 minutes, or 90 minutes postexercise. Glycogen concentration of the C+P group was greater than that of the CHO group at 90 minutes postexercise in both red (C+P, 28.3 ± 2.6 µmol/g vs CHO, 22.4 ± 2.0 µmol/g; P < .05) and white (C+P, 24.9 ± 2.4 µmol/g vs CHO, 17.64 ± 1.5 µmol/g; P < .01) quadriceps. Protein kinase B phosphorylation was greater in the C+P-30 group (the number following treatment group abbreviation refers to time [in minutes] of euthanasia following exercise) than the sedentary control and exercised control groups in red quadriceps at 30 minutes and in white quadriceps at 90 minutes postexercise. This difference was not observed in the CHO group. Phosphorylation of glycogen synthase was significantly reduced 30 minutes postexercise and returned to baseline levels by 90 minutes postexercise in both CHO- and C+P-supplemented groups, with no difference between supplements. These results demonstrated that the addition of protein to a carbohydrate supplement will enhance the rate of muscle glycogen restoration postexercise and may involve facilitation of the glucose transport process.

A low carbohydrate-protein supplement improves endurance performance in female athletes.

The purpose of this study was to investigate if a low mixed carbohydrate (CHO) plus moderate protein (PRO) supplement, provided during endurance exercise, would improve time to exhaustion (TTE) in comparison to a traditional 6% CHO supplement. Fourteen (n = 14) trained female cyclists and triathletes cycled on 2 separate occasions for 3 hours at intensities varying between 45 and 70% VO2max, followed by a ride to exhaustion at an intensity approximating the individual's ventilatory threshold average 75.06% VO2max. Supplements (275 mL) were provided every 20 minutes during exercise and were composed of a CHO mixture (1% each of dextrose, fructose, and maltodextrin) + 1.2% PRO (CHO + PRO) or 6% dextrose only (CHO). The TTE was significantly greater with CHO + PRO in comparison to with CHO (49.94 ± 7.01 vs. 42.36 ± 6.21 minutes, respectively, p < 0.05). Blood glucose was significantly lower during the CHO + PRO trial (4.07 ± 0.12 mmol · L(-1)) compared to during the CHO trial (4.47 ± 0.12 mmol · L(-1)), with treatment × time interactions occurring from 118 minutes of exercise until exhaustion (p < 0.05). Results from the present study suggest that the addition of a moderate amount of PRO to a low mixed CHO supplement improves endurance performance in women above that of a traditional 6% CHO supplement. Improvement in performance occurred despite CHO + PRO containing a lower CHO and caloric content. It is likely that the greater performance seen with CHO + PRO was a result of the CHO-PRO combination and the use of a mixture of CHO sources.

An amino acid mixture improves glucose tolerance and insulin signaling in Sprague-Dawley rats.

The aims of this investigation were to evaluate the effect of an amino acid supplement on the glucose response to an oral glucose challenge (experiment 1) and to evaluate whether differences in blood glucose response were associated with increased skeletal muscle glucose uptake (experimental 2). Experiment 1 rats were gavaged with either glucose (CHO), glucose plus an amino acid mixture (CHO-AA-1), glucose plus an amino acid mixture with increased leucine concentration (CHO-AA-2), or water (PLA). CHO-AA-1 and CHO-AA-2 had reduced blood glucose responses compared with CHO, with no difference in insulin among these treatments. Experiment 2 rats were gavaged with either CHO or CHO-AA-1. Fifteen minutes after gavage, a bolus containing 2-[(3)H]deoxyglucose and [U-(14)C]mannitol was infused via a tail vein. Blood glucose was significantly lower in CHO-AA-1 than in CHO, whereas insulin responses were similar. Muscle glucose uptake was higher in CHO-AA-1 compared with CHO in both fast-twitch red (8.36 ± 1.3 vs. 5.27 ± 0.7 µmol·g(-1)·h(-1)) and white muscle (1.85 ± 0.3 vs. 1.11 ± 0.2 µmol·g(-1)·h(-1)). There was no difference in Akt/PKB phosphorylation between treatment groups; however, the amino acid treatment resulted in increased AS160 phosphorylation in both muscle fiber types. Glycogen synthase phosphorylation was reduced in fast-twitch red muscle of CHO-AA-1 compared with CHO, whereas mTOR phosphorylation was increased. These differences were not noted in fast-twitch white muscle. These findings suggest that amino acid supplementation can improve glucose tolerance by increasing skeletal muscle glucose uptake and intracellular disposal through enhanced intracellular signaling.

The effect of a low carbohydrate beverage with added protein on cycling endurance performance in trained athletes.

Ingesting carbohydrate plus protein during prolonged variable intensity exercise has demonstrated improved aerobic endurance performance beyond that of a carbohydrate supplement alone. The purpose of the present study was to determine if a supplement containing a mixture of different carbohydrates (glucose, maltodextrin, and fructose) and a moderate amount of protein given during endurance exercise would increase time to exhaustion (TTE), despite containing 50% less total carbohydrate than a carbohydrate-only supplement. We also sought post priori to determine if there was a difference in effect based on percentage of ventilatory threshold (VT) at which the subjects cycled to exhaustion. Fifteen trained male and female cyclists exercised on 2 separate occasions at intensities alternating between 45 and 70% VO2max for 3 hours, after which the workload increased to ∼74-85% VO2max until exhaustion. Supplements (275 mL) were provided every 20 minutes during exercise, and these consisted of a 3% carbohydrate/1.2% protein supplement (MCP) and a 6% carbohydrate supplement (CHO). For the combined group (n = 15), TTE in MCP did not differ from CHO (31.06 ± 5.76 vs. 26.03 ± 4.27 minutes, respectively, p = 0.064). However, for subjects cycling at or below VT (n = 8), TTE in MCP was significantly greater than for CHO (45.64 ± 7.38 vs. 35.47 ± 5.94 minutes, respectively, p = 0.006). There were no significant differences in TTE for the above VT group (n = 7). Our results suggest that, compared to a traditional 6% CHO supplement, a mixture of carbohydrates plus a moderate amount of protein can improve aerobic endurance at exercise intensities near the VT, despite containing lower total carbohydrate and caloric content.

Improved cycling time-trial performance after ingestion of a caffeine energy drink.

CONTEXT: Not all athletic competitions lend themselves to supplementation during the actual event, underscoring the importance of preexercise supplementation to extend endurance and improve exercise performance. Energy drinks are composed of ingredients that have been found to increase endurance and improve physical performance. PURPOSE: The purpose of the study was to investigate the effects of a commercially available energy drink, ingested before exercise, on endurance performance. METHODS: The study was a double-blind, randomized, crossover design. After a 12-hr fast, 6 male and 6 female trained cyclists (mean age 27.3 +/- 1.7 yr, mass 68.9 +/- 3.2 kg, and VO2 54.9 +/- 2.3 ml x kg-1 x min-1) consumed 500 ml of either flavored placebo or Red Bull Energy Drink (ED; 2.0 g taurine, 1.2 g glucuronolactone, 160 mg caffeine, 54 g carbohydrate, 40 mg niacin, 10 mg pantothenic acid, 10 mg vitamin B6, and 10 microg vitamin B12) 40 min before a simulated cycling time trial. Performance was measured as time to complete a standardized amount of work equal to 1 hr of cycling at 70% Wmax. RESULTS: Performance improved with ED compared with placebo (3,690 +/- 64 s vs. 3,874 +/- 93 s, p < .01), but there was no difference in rating of perceived exertion between treatments. b-Endorphin levels increased during exercise, with the increase for ED approaching significance over placebo (p = .10). Substrate utilization, as measured by open-circuit spirometry, did not differ between treatments. CONCLUSION: These results demonstrate that consuming a commercially available ED before exercise can improve endurance performance and that this improvement might be in part the result of increased effort without a concomitant increase in perceived exertion.

The effect of a carbohydrate and protein supplement on resistance exercise performance, hormonal response, and muscle damage.

The purpose of this study was to determine whether resistance exercise performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO-PRO; 6.2% and 1.5% concentrations). Thirty-four male subjects (age: 21.5 +/- 1.7 years; height: 177.3 +/- 1.1 cm; weight: 77.2 +/- 2.2 kg) completed 3 sets of 8 repetitions at their 8 repetition maximum to volitional fatigue. The exercise order consisted of the high pull, leg curl, standing overhead press, leg extension, lat pull-down, leg press, and bench press. In a double-blind, posttest-only control group design, subjects consumed 355 ml of either CHO-PRO or placebo (electrolyte and artificial sweetener beverage) 30 minutes prior to exercise, 177 ml immediately prior to exercise, 177 ml halfway through the exercise bout, and 355 ml immediately following the exercise bout. There were no significant differences between groups relative to exercise performance. Cortisol was significantly elevated in the placebo group compared to the CHO-PRO group at 24 hours postexercise. Insulin was significantly elevated immediately pre-exercise, after the fourth lift, immediately postexercise, 1 hour, and 6 hours postexercise in CHO-PRO compared to the placebo group. Myoglobin levels in the placebo group approached significance halfway through the exercise bout and at 1 hour postexercise (p = 0.06 and 0.07, respectively) and were significantly elevated at 6 hours postexercise compared to the CHO-PRO group. Creatine kinase levels were significantly elevated in the placebo group at 24 hours postexercise compared to the CHO-PRO group. The CHO-PRO supplement did not improve performance during a resistance exercise bout, but appeared to reduce muscle damage, as evidenced by the responses of both myoglobin and creatine kinase. These results suggest the use of a CHO-PRO supplement during resistance training to reduce muscle damage and soreness.

Effect of a carbohydrate-protein supplement on endurance performance during exercise of varying intensity.

Increasing the plasma glucose and insulin concentrations during prolonged variable intensity exercise by supplementing with carbohydrate has been found to spare muscle glycogen and increase aerobic endurance. Furthermore, the addition of protein to a carbohydrate supplement will enhance the insulin response of a carbohydrate supplement. The purpose of the present study was to compare the effects of a carbohydrate and a carbohydrate-protein supplement on aerobic endurance performance. Nine trained cyclists exercised on 3 separate occasions at intensities that varied between 45% and 75% VO2max for 3 h and then at 85% VO2max until fatigued. Supplements (200 ml) were provided every 20 min and consisted of placebo, a 7.75% carbohydrate solution, and a 7.75% carbohydrate/1.94% protein solution. Treatments were administered using a double-blind randomized design. Carbohydrate supplementation significantly increased time to exhaustion (carbohydrate 19.7 +/- 4.6 min vs. placebo 12.7 +/- 3.1 min), while the addition of protein enhanced the effect of the carbohydrate supplement (carbohydrate-protein 26.9 +/- 4.5 min, p < .05). Blood glucose and plasma insulin levels were elevated above placebo during carbohydrate and carbohydrate-protein supplementation, but no differences were found between the carbohydrate and carbohydrate-protein treatments. In summary, we found that the addition of protein to a carbohydrate supplement enhanced aerobic endurance performance above that which occurred with carbohydrate alone, but the reason for this improvement in performance was not evident.