CHO Oxidation Research Articles

Insight into the Reaction Mechanisms of Methanol on PtRu/Pt(111): A Density Functional Study

Periodic DFT calculations have been performed to systematically investigate the mechanisms of methanol decomposition and oxidation on the PtRu/Pt(111) surface. Geometries and energies for the primary species involved are analyzed and the reaction network has been mapped out. The calculation shows that among three initial CH, OH, and CO bond scissions of methanol, the OH bond scission is found to be the most favorable and bears a lower energy barrier than the desorption of methanol. The decomposition of CH3O occurs via the path CH3O→CH2O→CHO→CO with the limiting step of the first dehydrogenation. Although the oxidation of CO is hindered by a high barrier, the CHO oxidation to CHOOH could occur facilely. Further decomposition of formic acid to CO2 and/or CO could occur via four possible pathways, that is, initial CH, OH, and CO bond activations as well as simultaneous activation of CH and CO bonds, where the first pathway, HCOOH→COOH→CO2, is the most favorable from a kinetic point of view. Compared to that on Pt(111), methanol on PtRu/Pt(111) prefers to decomposition rather than desorption and then oxidation via the favorable non-CO path with a lower rate-determining energy barrier of CH3O→CH2O for the whole reaction, which indicates that PtRu alloy can improved tolerance toward CO poisoning compared with pure Pt.

Altering fatty acid availability does not impair prolonged, continuous running to fatigue: evidence for carbohydrate dependence.

We determined the effect of suppressing lipolysis via administration of nicotinic acid (NA) on fuel substrate selection and half-marathon running capacity. In a single-blinded, Latin square design, 12 competitive runners completed four trials involving treadmill running until volitional fatigue at a pace based on 95% of personal best half-marathon time. Trials were completed in a fed or overnight fasted state: 1) carbohydrate (CHO) ingestion before (2 g CHO·kg(-1)·body mass(-1)) and during (44 g/h) [CFED]; 2) CFED plus NA ingestion [CFED-NA]; 3) fasted with placebo ingestion during [FAST]; and 4) FAST plus NA ingestion [FAST-NA]. There was no difference in running distance (CFED, 21.53 ± 1.07; CFED-NA, 21.29 ± 1.69; FAST, 20.60 ± 2.09; FAST-NA, 20.11 ± 1.71 km) or time to fatigue between the four trials. Concentrations of plasma free fatty acids (FFA) and glycerol were suppressed following NA ingestion irrespective of preexercise nutritional intake but were higher throughout exercise in FAST compared with all other trials (P < 0.05). Rates of whole-body CHO oxidation were unaffected by NA ingestion in the CFED and FAST trials, but were lower in the FAST trial compared with the CFED-NA trial (P < 0.05). CHO was the primary substrate for exercise in all conditions, contributing 83-91% to total energy expenditure with only a small contribution from fat-based fuels. Blunting the exercise-induced increase in FFA via NA ingestion did not impair intense running capacity lasting ∼85 min, nor did it alter patterns of substrate oxidation in competitive athletes. Although there was a small but obligatory use of fat-based fuels, the oxidation of CHO-based fuels predominates during half-marathon running.

HIGH-INTENSITY INTERVAL EXERCISE IN CHRONIC HEART FAILURE: COMPARISON OF CARBOHYDRATE AND LIPID OXIDATION

high-intensity interval exercise has been extensively used with athletes and healthy subjects. There are a few evidences that it could improves physiology and functional capacity in heart failure patients, but still some answers about muscle metabolism need to be addressed. substrate oxidation was compared during 4 different high intensity intermittent exercise (HIIE) protocols in patients with heart failure and reduced ejection fraction (HFREF). Eighteen males (56±17 years, LVEF: 28±7%) randomly performed 4 HIIE with measurement of gas exchange. Exercise intensity protocols were set at 100% of peak power output (PPO). Interval duration was 30 seconds (A and B) or 90 seconds (C and D), and recovery was passive (A and C) or active (50% of PPO in B and D). Energy expenditure was calculated using Weir equation and substrate oxidation (glucose: CHO, and lipid) was calculated by the Frayn equation (for quantitative measure) and from a table of non-protein respiratory quotient (qualitative measure) using gas exchange analysis. mean O2peak was 17.8 ± 4.6 ml/min/kg (or 1.54 ± 4.6 L/min) and peak power output was 109 ± 31 Watts. At rest, fat oxidation averaged 0.13 ± 0.04 g/min, representing 68 ± 22 % of total substrate utilisation. CHO oxidation averaged 0.16 ± 0.1 g/min representing 31 ± 22% of total. During exercise, absolute CHO oxidation significantly decreased and absolute lipid oxidation significantly increased in each HIIE protocol (P<0.0001). Protocol B induced higher energy expenditure after 8-10 minutes of exercise compare to passive recovery modes (A and C) (P<0.0001). Short duration intervals with passive recovery (mode A) resulted in significantly lower CHO oxidation in absolute terms compare to modes with active recovery (B and D) (P<0.0001). In relative terms (%), CHO oxidation in mode A was significantly lower than mode C only, after 8-10 minutes of exercise. Lipid oxidation in absolute terms was significantly lower in mode C compare to the other 3 modes of HIIE at time 8-10 min whereas in relative terms it was significantly lower than mode A only (P<0.0001). All together, these 4 HIIE protocols showed increased lipid oxidation over time, and short interval duration with passive recovery showed higher lipid oxidation compared to the others. the choice of an active mode during HIIE may favors glucose oxidation during exercise in patients with HFREF, if the improvement of glucose metabolism is targeted.

Breakfasts Higher in Protein Increase Postprandial Energy Expenditure, Increase Fat Oxidation, and Reduce Hunger in Overweight Children from 8 to 12 Years of Age1–3

Background: Currently 1 in every 3 children aged 2–19 y is overweight or obese. Breakfast is a key component of a healthy diet and has the potential to affect children's health.Objective: The objective of this study was to determine whether consumption of a protein-based breakfast (PRO) increases postprandial energy metabolism and substrate oxidation, reduces hunger, and reduces food intake at lunch compared with a carbohydrate-based breakfast (CHO) in normal weight (NW) vs. overweight/obese (OW) children.Methods: A randomized, crossover-design study was conducted in NW (n = 16; 33 ± 1 kg) and OW (n = 13; 46 ± 2 kg) children (10 ± 1 y). Participants were served either a PRO [344 kcal, 21% protein (18 g), 52% carbohydrate, and 27% fat] or CHO [327 kcal, 4% protein (3 g), 67% carbohydrate, and 29% fat]. Energy expenditure (EE), substrate oxidation, appetite, and blood glucose were measured over a 4 h period. Four hour postprandial participants were provided with access to a lunch buffet and food intake was recorded.Results: After breakfast, OW children in the PRO group had higher (P < 0.0001) EEs and fat oxidation over the 4 h period than did the NW children in the CHO and PRO groups. There was no difference in postprandial EE or carbohydrate oxidation between the CHO and PRO groups over the 4 h period; however, fat oxidation was 16% higher (P < 0.05) after the PRO than the CHO and postprandial carbohydrate oxidation at 4 h was 32% higher after the PRO than the CHO (P < 0.01), independent of weight group. All participants had decreased feelings of hunger (−14%; P < 0.01) and increased fullness (+32%; P < 0.05) after the PRO than the CHO. Finally, there was no difference in food intake within the NW and OW groups.Conclusion: This study indicates that breakfast macronutrient composition affects postprandial responses in both NW and OW children. A PRO increases postprandial EE and fat oxidation, reduces hunger, and increases satiety when compared with a carbohydrate-based breakfast.

Mouth Rinsing With Carbohydrate Solutions at the Postprandial State Fail to Improve Performance During Simulated Cycling Time Trials.

Mouth rinsing with carbohydrate (CHO) solutions during cycling time trials results in performance enhancements; however, most studies have used approximately 6% CHO solutions. Therefore, the purpose of this study was to compare the effectiveness of mouth rinsing with 4, 6, and 8% CHO solutions on 1-hour simulated cycling time trial performance. On 4 occasions, 7 trained male cyclists completed at the postprandial period, a set amount of work as fast as possible in a randomized counterbalanced order. The subjects rinsed their mouth for 5 seconds, on completion of each 12.5% of the trial, with 25 ml of a non-CHO placebo and 4, 6, and 8% CHO solutions. No additional fluids were consumed during the time trial. Heart rate (HR), ratings of perceived exertion (RPE), thirst (TH), and subjective feelings (SF) were recorded after each rinse. Furthermore, blood samples were drawn every 25% of the trial to measure blood glucose and blood lactate concentrations, whereas whole-body CHO oxidation was monitored continuously. Time to completion was not significant between conditions with the placebo, 4, 6, and 8% conditions completing the trials in 62.0 ± 3.0, 62.8 ± 4.0, 63.4 ± 3.4, and 63 ± 4.0 minutes, respectively. There were no significant differences between conditions in any of the variables mentioned above; however, significant time effects were observed for HR, RPE, TH, and SF. Post hoc analysis showed that TH and SF of subjects in the CHO conditions but not in the placebo were significantly increased by completion of the time trial. In conclusion, mouth rinsing with CHO solutions did not impact 1-hour cycling performance in the postprandial period and in the absence of fluid intake. Our findings suggest that there is scope for further research to explore the activation regions of the brain and whether they are receptive to CHO dose, before specific recommendations for athletic populations are established. Consequently, mouth rinsing as a practical strategy for coaches and athletes is questionable under specific conditions and should be carefully considered before its inclusion. Emphasis should be focused on appropriate dietary and fluid strategies during training and competition.

Extreme Variation of Nutritional Composition and Osmolality of Commercially Available Carbohydrate Energy Gels.

The provision of exogenous carbohydrate (CHO) in the form of energy gels is regularly practiced among endurance and team sport athletes. However, in those instances where athletes ingest suboptimal fluid intake, consuming gels during exercise may lead to gastrointestinal (GI) problems when the nutritional composition of the gel is not aligned with promoting gastric emptying. Accordingly, the aim of the current study was to quantify the degree of diversity in nutritional composition of commercially available CHO gels intended for use in the global sports nutrition market. We surveyed 31 product ranges (incorporating 51 flavor variants) from 23 brands (Accelerade, CNP, High5, GU, Hammer, Maxim, Clif, USN, Mule, Multipower, Nectar, Carb- Boom, Power Bar, Lucozade, Shotz, TORQ, Dextro, Kinetica, SiS, Zipvit, Maxifuel, Gatorade and Squeezy). Gels differed markedly in serving size (50 ± 22 g: 29-120), energy density (2.34 ± 0.7 kcal/g: 0.83-3.40), energy content (105 ± 24 kcal: 78-204), CHO content (26 ± 6 g: 18-51) and free sugar content (9.3 ± 7.0 g: 0.6-26.8). Most notably, gels displayed extreme variation in osmolality (4424 ± 2883 mmol/kg: 303-10,135) thereby having obvious implications for both GI discomfort and the total fluid intake likely required to optimize CHO delivery and oxidation. The large diversity of nutritional composition of commercially available CHO gels illustrate that not all gels should be considered the same. Sports nutrition practitioners should therefore consider the aforementioned variables to make better-informed decisions regarding which gel product best suits the athlete's specific fueling and hydration requirements.

Substrate Utilization At Rest And Following A Meal After Acute Caloric Restriction

Carbohydrates (CHO) and fat are the predominant substrates oxidized for energy by humans. At rest, when energy demands are low, there is typically a small preference given to fat over CHO oxidation. However, following a meal or during exercise, both times of increased energy demand, many factors influence the type of fuels utilized. A non-invasive and validated technique for estimating substrate utilization is the respiratory exchange ratio (RER; VCO2/VO2). PURPOSE: Determine substrate utilization at rest following a standardized meal after 24hrs of controlled feeding and exercise. METHODS: Ten healthy men (22.8±2.7yrs) performed three trials in random order each consisting of 24hr controlled feeding (57/22/21% CHO/fat/protein) to provide three levels of energy availability: an energy balance trial, and a moderate and mild caloric restriction trials (45, 25 & 35kcal/kg/FFM, respectively). At the end of each 24hr period of controlled feeding, participants ran on a treadmill to expend 10kcal/kg/FFM (684.6±43.3kcal) at 60%VO2max. They returned the next morning for baseline measurements, a mixed-meal challenge (50/39/11% CHO/fat/protein), and subsequent measurements over the next three hours. The RER data was collected in 5min increments interspersed by 10min of no data collection. Data are reported as mean±stdev; repeated measures ANOVAs were utilized with significance accepted as p<0.05. RESULTS: While there were no significant interactions among trials, the collapsed data revealed a main effect for time where RER was higher at 120-125, 135-140, and 165-170min after the meal challenge compared to fasting RER. Moreover, the unique finding gleaned from this investigation was that in the collapsed data among trials, the RER was significantly lower for the 25kcal/kg/FFM trial compared to the 35 and 45kcal/kg/FFM trials (0.84±0.02 vs. 0.86±0.03 and 0.87±0.03, respectively). CONCLUSION: The contribution of CHO and fat oxidation for energy demands is influenced by many factors, but in this group of men, a novel finding was that moderate caloric restriction had an effect on substrate utilization. Funded in part by the MWACSM Student Research Grant, Joseph Allen Butts Award, and the OU-College of Health Sciences and Professions Student Research Grant

Dr M Posthumus

PURPOSE: It has previously been shown that eccentric cyling resulted greater fat utilisation during and after cycling at the same power output. The aim of this study was to compare the effects of concentric and eccentric biased cycling on substrate oxidation and utilisation as well as power output, heart rate, energy expenditure and efficiency during bouts matched to either oxygen consumption or perceived exertion. METHODS: Sixteen recreationally fit males (24 ± 2 years) performed two 30 min bouts of concentric and eccentric cycling, one week apart. Each bout was comprised of two sets of cycling; 15 min at 50 % VO2max and 15 min at RPE clamped (8/20, 13/20 and 16/20) steps of 5 minutes each, with 10 min of passive rest between sets. Relative VO2, relative power output, relative heart rate, RER, fat oxidation, CHO oxidation, energy expenditure and efficiency were assessed during each cycling bout. RESULTS: Relative VO2 was significantly greater during concentric cycling at 8/20 (p<.001), 13/20 (p<.001) and 16/20 (p<.001) RPEs. Relative power output was significantly greater during eccentric cycling at 50 % VO2max at 5, 10 and 15 min (p<.001, all) and during eccentric cycling at the same perceived exertion (p < .001). Relative heart rate was significantly greater during eccentric cycling at 50 % VO2max (p=.002) and during concentric cycling at 13/20 (p<.001) and 16/20 (p<.001). RER was significantly greater during concentric cycling at 50 % VO2max (p=.002) and 13/20 (p<.001) and 16/20 (p<.001) RPE. Fat oxidation was significantly greater during eccentric cycling at 50 % VO2max (p=.002) and at 13/20 (p=.008) and 16/20 (p<.001) RPE while CHO oxidation was significantly greater during concentric cycling at 50 % VO2max (p=.001) and at 13/20 (p<.001) and 16/20 (p<.001) RPE. Total energy expenditure was significantly greater during concentric cycling at 50 % VO2max (p < .001) and at 13/20 (p<.001) and 16/20 (p<.001) RPE. Efficiency was significantly greater during eccentric cycling at 50 % VO2max (p<.001) and at perceived exertion (p<.001). CONCLUSIONS: Fat oxidation was significantly greater during eccentric cycling compared to concentric cycling at 50 % VO2max and fat oxidation increased as exercise intensity of eccentric cycling increased.

Effects Of Aerobic Exercise Training And Exercise Intensity On Skeletal Muscle Metabolic Function In Premenopausal Women

BACKGROUND: Aerobic training has been shown to improve mitochondrial bioenergetics and up-regulate proteins related to lipid metabolism. However, whether improvements in mitochondrial oxidation and translational proteins associated mitochondrial biogenesis and fatty acid transport (FA) occurs independent of negative energy balance (EB) is unclear. PURPOSE: To assess mitochondrial fatty acid (FA) and carbohydrate (CHO) oxidation in permeabilized muscle fibers, and proteins associated with mitochondrial biogenesis and FA transport under rigorously controlled EB conditions pre- and 12-weeks post aerobic exercise training (AET), and after an acute bout of moderate (MOD) or high (HI) intensity exercise in premenopausal women. METHODS: Participants were 7 women (age = 31±5; weight = 72 ± 11kg; BMI = 26 ± 4kg/m2). Testing was done prior to and after 12-weeks of aerobic exercise training (AET), and after an acute bout of moderate (MOD) or high (HI) intensity exercise in premenopausal women. Muscle biopsies were collected at baseline, 12-wks post, MOD, and HI. Mitochondrial FAO and CHO oxidation were quantified in permeabilized muscle fibers. Western blots were performed to determine PGC1α and carnitine palmitoyltransferase 1B (CPT1B) protein expression. Pre-test conditions were rigorously controlled for EB. RESULTS: Compared to baseline significant increases were observed following 12-wks post, MOD, and HI for State 3 (154%, 115%, and 163%), 4 (90%, 80%, and 128%), and maximum uncoupled respiration (137%, 97%, and 174%) rates when normalized to wet weight using malate and palmitoyl-carnitine as substrates (P 0.05). Importantly, there were no significant differences between 24-hr energy intake and EE across all time points, demonstrating tight control of EB over the 24hr period. CONCLUSION: These data demonstrate an enhanced mitochondrial fatty acid metabolism following 12-weeks of AET, and after a MOD or HI bout of acute exercise without any changes in EB. The increase in mitochondrial FA oxidation appears to be due to mitochondrial biogenesis after training and not intrinsic changes within existing mitochondria. These improvements occurred without any significant increases in PGC1α or CPT1B protein expression measured 24hrs following exercise, suggesting other potential mechanisms in which aerobic exercise may enhance mitochondrial FA oxidation.

Effect of Galactose Ingestion Before and During Exercise on Substrate Oxidation, Postexercise Satiety, and Subsequent Energy Intake in Females

Objective: To examine the effects of consuming a galactose carbohydrate (CHO) drink on substrate oxidation, postexercise satiety, and subsequent energy intake.Methods: Nine recreationally active eumenorrheic females undertook 3 trials, each consisting of running for 60 minutes at 65% VO2peak followed immediately by a 90-minute rest period. Prior to (300 ml) and at 15-minute intervals during exercise (150 ml), participants consumed either a glucose (GLU: GI 89) or galactose (GAL: GI 20) drink, each of which contained 45 g of CHO, or an artificially sweetened placebo (PLA). Following the rest period, participants were provided with an ad libitum test lunch and asked to record food intake for the remainder of the day.Results: Plasma glucose was significantly greater throughout exercise and rest following the GLU trial compared with the GAL and PLA trials (P < 0.05); however there were no differences in CHO oxidation. Hunger was significantly lower (P < 0.05) throughout the GAL compared to the GLU and PLA trials. There were no significant differences between trials for energy intake during the postexercise meal. Overall net energy balance for the 24 hours was negative in both the GAL (−162 ± 115 kcal; P < 0.05 vs GLU) and PLA trials (−49 ± 160 kcal).Conclusions: Results demonstrate that ingesting a solution containing GAL before and during exercise can positively impact postexercise satiety and energy balance throughout the day, compared to a more readily available and widely consumed form of CHO. Despite this, there appears to be no apparent benefit in consuming a CHO beverage on fuel utilization for this moderate exercise intensity and duration.

Fatigue Mechanisms During Repeated Exercise

Little is known about fatigue mechanisms in a repeated exercise bout or the potential for protein in the restoration of exercise capacity. PURPOSE: To examine metabolic responses in the late stages of repeated exhaustive exercise when a carbohydrate-protein (CHO-P) supplement is ingested during short-term recovery. METHODS: Six runners (VO2max 64 ± 4 ml·kg-1·min-1) completed an initial treadmill run to exhaustion at 70% VO2max (Run-1) and repeated this 4 h later (Run-2). At 30 min intervals during recovery, a carbohydrate (CHO; 1.2 g sucrose·kg-1·h-1) or an isocaloric CHO-P solution (0.8 g sucrose·kg-1·h-1 and 0.4 g whey protein hydrolysate·kg-1·h-1) was ingested. Blood, muscle biopsy (analysis pending) and expired gas samples were taken at time-points necessary to explore the onset of fatigue. Data are mean ± SD unless otherwise stated. RESULTS: Run time to exhaustion with CHO and CHO-P was 81 ± 17 versus 84 ± 19 min in Run-1 (p=0.37) and 51 ± 13 versus 49 ± 15 min in Run-2 (p=0.43). The insulinemic response during recovery was higher in CHO-P than CHO (47 ± 18 versus 31 ± 7 nmol·240 min·l-1; p=0.05). Plasma glucose concentrations during Run-2 were similar in CHO and CHO-P and no differences were shown at the point of fatigue (CHO: 4.5 ± 0.8 and CHO-P: 4.4 ± 0.3 mmol·l-1; p=0.84). Plasma non-esterified fatty acid (NEFA) concentrations were also similar throughout Run-2 in both treatments with CHO (0.55 ± 0.25 mmol·l-1) and CHO-P (0.43 ± 0.26 mmol·l-1; p=0.29). Whole-body CHO oxidation was 3.1 ± 1.1 g·min-1 at fatigue with CHO; similar to CHO-P at the same absolute time-point (2.8 ± 0.9 g·min-1; p=0.34). Moreover, no differences were observed in fat oxidation between CHO (0.2 ± 0.3 g·min-1) and CHO-P (0.3 ± 0.4 g·min-1; p=0.36). CONCLUSION: Despite an increased insulinemic response with CHO-P ingestion during recovery, the restoration of exercise capacity and substrate utilization was similar between treatments. Thus, substituting a fraction of carbohydrate for protein in a recovery solution may be beneficial for other protein-mediated processes. Funder: Saudi Arabian Ministry of Higher Education.

High Carbohydrate Diet Induces Faster Final Sprint and Overall 10,000-m Times of Young Runners.

This study analyzed the pacing employed by young runners in 10,000 m time-trials under 3 dietary regimens of different carbohydrate (CHO) intakes. Nineteen boys (13-18 years) ate either their normal CHO diet (56% CHO), high (70% CHO), or low (25% CHO) CHO diets for 48 hr; the boys then performed a 10,000 m run (crossover design). The high CHO diet led to faster final sprint (14.4 ± 2.2 km·h⁻¹) and a better performance (50.0 ± 7.0 min) compared with the low CHO diet (13.3 ± 2.4 km·h⁻¹ and 51.9 ± 8.3 min, respectively, p < .05). However, the final sprint and performance time in the high CHO or low CHO diets were statistically not significantly different from the normal CHO diet (13.8 ± 2.2 km·h⁻¹ and 50.9 ± 7.4 min; p > .05). CHO oxidation rate during the constant load exercise at 65% of VO2max was elevated in high CHO diet (1.05 ± 0.38 g·min⁻¹) compared with low CHO diet (0.63 ± 0.36 g·min⁻¹). The rating of perceived exertion increased linearly throughout the trial, independently of the dietary regimen. In conclusion, the high CHO diet induced higher CHO oxidation rates, increased running speed in the final 400 m and enhanced overall running performance, compared with low CHO.

Fasting substrate oxidation at rest assessed by indirect calorimetry: is prior dietary macronutrient level and composition a confounder?

Indirect calorimetry, the measurement of O₂ consumption and CO₂ production, constitutes an invaluable tool as the most common method for analyzing whole-body energy expenditure, and also provides an index of the nature of macronutrient substrate oxidation--namely, carbohydrate (CHO) versus fat oxidation. The latter constitutes a key etiological factor in obesity as this condition can only develop when total fat oxidation is chronically lower than total exogenous fat intake. The standardization of indirect calorimetry measurements is essential for accurately tracking the relative proportion of energy expenditure derived from CHO and fat oxidation. Here we analyze literature data to show that the average fasting respiratory quotient typically shifts from approximately 0.80 to 0.90 (indicating a doubling of resting CHO oxidation) in response to a switch in dietary CHO intake (as % energy) from 30 to 60%. This underscores the importance of taking into account dietary macronutrient composition prior to indirect calorimetry studies in the interpretation of data on substrate utilization and oxidation.

High cycling cadence reduces carbohydrate oxidation at given low intensity metabolic rate.

Cycling cadence (RPM)-related differences in blood lactate concentration (BLC) increase with increasing exercise intensity, whilst corresponding divergences in oxygen uptake (O2) and carbon dioxide production (CO2) decrease. Aim of the present study was to test whether a higher RPM reduces the fraction (%) of the O2 used for carbohydrate oxidation (relCHO) at a given BLC. Eight males (23.9 ± 1.6 yrs; 177 ± 3 cm; 70.3 ± 3.4 kg) performed incremental load tests at 50 and 100 RPM. BLC, O2 and CO2 were measured. At respiratory exchange ratios (RER) < 1, relCHO were calculated and the constant determining 50 % relCHO (kCHO) was approximated as a function of the BLC. At submaximal workload O2, CO2, and relCHO were lower (all p < 0.002; η2 > 0.209) at 50 than at 100 RPM. No differences were observed in O2peak (3.96 ± 0.22 vs. 4.00 ± 0.25 l · min−1) and RERpeak (1.18 ± 0.02 vs. 1.15 ± 0.02). BLC was lower (p < 0.001; η2 = 0.680) at 50 than at 100 RPM irrespective of cycling intensity. At 50 RPM, kCHO (4.2 ± 1.4 (mmol · l−1)3) was lower (p = 0.043; η2 = 0.466) than at 100 RPM (5.9 ± 1.9 (mmol · l−1)3). This difference in kCHO reflects a reduced CHO oxidation at a given BLC at 100 than at 50 RPM. At a low exercise intensity, a higher cycling cadence can substantially reduce the reliance on CHO at a given metabolic rate and/or BLC.

Self-selecting Fluid Intake while Maintaining High Carbohydrate Availability Does not Impair Half-marathon Performance

We aimed to test the hypothesis that self-selecting fluid intake but maintaining high exogenous CHO availability (60 g/h) does not compromise half-marathon performance. 15 participants completed 3 half-marathons while drinking a 6% CHO solution to guidelines (DRINK) or a non-caloric solution in self-selected volumes when consuming 3×glucose (20 g) gels (G-GEL) or glucose-fructose (13 g glucose+7 g fructose) gels (GF-GEL) per hour. Fluid intake (DRINK: 1 557±182, G-GEL: 473±234, GF-GEL: 404±144 ml) and percent body mass loss (DRINK: - 0.8±0.9, G-GEL: - 2.0±0.6, GF-GEL: -2.3±1.1) were different (P<0.05) between conditions, though race time did not differ (DRINK: 110.6±14.4, G-GEL: 110.3±14.6, GF-GEL: 113.7±12.8 min). In G-GEL, there was a positive correlation (P<0.05) between body mass loss and race time. Plasma glucose was lower (P<0.05) in GF-GEL compared with other conditions, and total CHO oxidation (DRINK: 3.2±0.5, G-GEL: 3.0±0.4, GF-GEL: 2.6±0.4 g/min) was lower (P=0.06) in this trial. Self-selecting fluid intake but maintaining high CHO availability does not impair half-marathon performance. Additionally, consuming glucose-fructose mixtures in sub-optimal amounts reduces plasma glucose and total rates of CHO oxidation.

The effect of almond consumption on elements of endurance exercise performance in trained athletes.

BackgroundAlmonds are a healthy tree nut food with high nutrient density. Their consumption has been shown to ameliorate oxidative stress, inflammation, etc. The objective of the study was to examine the effect of almonds on elements of endurance exercise performance in trained athletes.MethodsA 10-week crossover, placebo controlled study was conducted. Eight trained male cyclists and two triathletes were randomly assigned to consume 75 g/d whole almonds (ALM) or isocaloric cookies (COK) with equal subject number. They consumed the assigned food for 4 wks and then the alternate food for another 4 wks. They underwent 3 performance tests including 125-min steady status exercise (SS) and 20-min time trial (TT) on an indoor stationary trainer at the start of the study (BL) and at the end of each intervention phase. Venous blood was collected in the morning prior to the performance test for biochemical measurements and finger blood during the test for glucose determination. Carbohydrate and fat oxidation, energy expenditure, and oxygen use were calculated using respiratory gas analysis.ResultsALM increased cycling distance during TT by 1.7 km as compared BL (21.9 vs. 20.2 km, P = 0.053) and COK increased 0.6 km (20.8 vs. 20.2 km, P > 0.05). ALM, but not COK, led to higher CHO and lower fat oxidation and less oxygen consumption during TT than BL (P < 0.05), whereas there was no significant difference in heart rate among BL, ALM and COK. ALM maintained higher blood glucose level after TT than COK (P < 0.05). ALM had higher vitamin E and haemoglobin and lower serum free fatty acid (P < 0.05), slightly elevated serum arginine and nitric oxide and plasma insulin (P > 0.05) than BL, and a higher total antioxidant capacity than COK (P < 0.05).ConclusionsWhole almonds improved cycling distance and the elements related to endurance performance more than isocaloric cookies in trained athletes as some nutrients in almonds may contribute to CHO reservation and utilization and effective oxygen utilization. The results suggest that almonds can be incorporated into diets of those who undertake exercise training for performance improvement.

Systematic review: Carbohydrate supplementation on exercise performance or capacity of varying durations.

This systematic review examines the efficacy of carbohydrate (CHO) supplementation on exercise performance of varying durations. Included studies utilized an all-out or endurance-based exercise protocol (no team-based performance studies) and featured randomized interventions and placebo (water-only) trial for comparison against exclusively CHO trials (no other ingredients). Of the 61 included published performance studies (n = 679 subjects), 82% showed statistically significant performance benefits (n = 50 studies), with 18% showing no change compared with placebo. There was a significant (p = 0.0036) correlative relationship between increasing total exercise time and the subsequent percent increase in performance with CHO intake versus placebo. While not mutually exclusive, the primary mechanism(s) for performance enhancement likely differs depending on the duration of the exercise. In short duration exercise situations (∼1 h), oral receptor exposure to CHO, via either mouthwash or oral consumption (with enough oral contact time), which then stimulates the pleasure and reward centers of the brain, provide a central nervous system-based mechanism for enhanced performance. Thus, the type and (or) amount of CHO and its ability to be absorbed and oxidized appear completely irrelevant to enhancing performance in short duration exercise situations. For longer duration exercise (>2 h), where muscle glycogen stores are stressed, the primary mechanism by which carbohydrate supplementation enhances performance is via high rates of CHO delivery (>90 g/h), resulting in high rates of CHO oxidation. Use of multiple transportable carbohydrates (glucose:fructose) are beneficial in prolonged exercise, although individual recommendations for athletes should be tailored according to each athlete's individual tolerance.

Comparison of the Effects of Glucose and Fructose on Exercise Metabolism, Perceived Exertion, and Recovery in Untrained Females

This double-blinded, crossover randomized controlled trial study was designed to establish if combined ingestion of glucose and fructose (GLU + FRU) at the moderate rate 0.5 g·min−1 would result in higher rates of carbohydrate (CHO) oxidation compared with glucose (GLU) alone. Eight untrained females (VO2max: 25.8 ± 3.2 mL·kg−1·min−1) cycled on two different occasions for 60 min at 50% of maximal power output (60% ± 1 % VO2max) and consumed 12% CHO solution of either providing 0.33 g·min−1 glucose + 0.17 g·min−1 fructose (GLU + FRUC) or 0.5 g·min−1 of glucose (GLU) alone. Heart rate (HR) and rate of perceived exertion (RPE) were assessed during exercise and subjective exercise experience assessed two days after each trial. CHO oxidation was not significantly different (P&gt;0.05) between GLU + FRU and GLU (0.8 ± 0.06 g·min−1 and 0.78 ± 0.05 g·min−1, resp.). CHO oxidation rates during the final 30 min of the recovery period were not significantly different between GLU + FRU and GLU (0.17 ± 0.04 g·min−1 and 0.14 ± 0.05 g·min−1, resp.). Experience of distress was significantly higher (P&lt;0.05) for GLU compared to GLU + FRU. The results reveal that consuming modest amounts of glucose plus fructose does not boost CHO oxidation above that of glucose alone during submaximal exercise.

Mouse strain differences in metabolic fluxes and function of ex vivo working hearts

In mice, genetic background is known to influence various parameters, including cardiac function. Its impact on cardiac energy substrate metabolism-a factor known to be closely related to function and contributes to disease development-is, however, unclear. This was examined in this study. In commonly used control mouse substrains SJL/JCrNTac, 129S6/SvEvTac, C57Bl/6J, and C57Bl/6NCrl, we assessed the functional and metabolic phenotypes of 3-mo-old working mouse hearts perfused ex vivo with physiological concentrations of (13)C-labeled carbohydrates (CHO) and a fatty acid (FA). Marked variations in various functional and metabolic flux parameters were observed among all mouse substrains, although the pattern observed differed for these parameters. For example, among all strains, C57Bl/6NCrl hearts had a greater cardiac output (+1.7-fold vs. SJL/JCrNTac and C57Bl/6J; P < 0.05), whereas at the metabolic level, 129S6/SvEvTac hearts stood out by displaying (vs. all 3 strains) a striking shift from exogenous FA (~-3.5-fold) to CHO oxidation as well as increased glycolysis (+1.7-fold) and FA incorporation into triglycerides (+2-fold). Correlation analyses revealed, however, specific linkages between 1) glycolysis, FA oxidation, and pyruvate metabolism and 2) cardiac work, oxygen consumption with heart rate, respectively. This implies that any genetically determined factors affecting a given metabolic flux parameter may impact on the associated functional parameters. Our results emphasize the importance of selecting the appropriate control strain for cardiac metabolic studies using transgenic mice, a factor that has often been neglected. Understanding the molecular mechanisms underlying the diversity of strain-specific cardiac metabolic and functional profiles, particularly the 129S6/SvEvTac, may ultimately disclose new specific metabolic targets for interventions in heart disease.

The ingestion of protein with a maltodextrin and fructose beverage on substrate utilisation and exercise performance

The study investigated the ingestion of maltodextrin, fructose, and protein on exogenous carbohydrate oxidation (CHOEXO) and exercise performance. Seven trained cyclists and (or) triathletes (maximal oxygen consumption, 59.20 ± 9.00 mL · kg(-1) · min(-1)) performed 3 exercise trials that consisted of 150 min of cycling at 50% maximal power output (160 ± 11 W), followed by a 60-km time trial. One of 3 beverages were randomly assigned during each trial and consumed at 15-min intervals: (i) 0.84 g · min(-1) maltodextrin + 0.52 g · min(-1) fructose + 0.34 g · min(-1) protein (MD+F+P); (ii) 1.10 g · min(-1) maltodextrin + 0.60 g · min(-1) fructose (MD+F); or (iii) 1.70 g · min(-1) maltodextrin (MD). CHO(EXO) and fuel utilisation were assessed via measurement of expired air (13)C content and indirect calorimetry, respectively. Mean total CHO oxidation (CHOTOT) rates were 2.35 ± 0.18, 2.76 ± 0.08, and 2.61 ± 0.17 g · min(-1) with MD, MD+F, and MD+F+P, respectively, although not significantly different. Peak CHO(EXO) rates with MD+F were significantly greater by 41.4% (p = 0.001) and 45.4% (p = 0.0001) compared with MD+F+P and MD, respectively (1.57 ± 0.22 g · min(-1), 1.11 ± 0.08 g · min(-1), and 1.08 ± 0.11 g · min(-1), respectively). Performance times were 2.2% and 5.0% faster with MD+F compared with MD+F+P and MD, respectively; however, they were not statistically significant. Ingestion of an MD-fructose-protein commercial sports beverage significantly reduced peak and mean CHO(EXO) rates compared with MD+F, but did not significantly influence CHOTOT. The addition of protein to an MD+F beverage did not enhance performance times.