Fructose-maltodextrin ratio in a carbohydrate-electrolyte solution differentially affects exogenous carbohydrate oxidation rate, gut comfort, and performance

Solutions containing multiple carbohydrates utilizing different intestinal transporters (glucose and fructose) show enhanced absorption, oxidation, and performance compared with single-carbohydrate solutions, but the impact of the ratio of these carbohydrates on outcomes is unknown. In a randomized double-blind crossover, 10 cyclists rode 150 min at 50% peak power, then performed an incremental test to exhaustion, while ingesting artificially sweetened water or one of three carbohydrate-salt solutions comprising fructose and maltodextrin in the respective following concentrations: 4.5 and 9% (0.5-Ratio), 6 and 7.5% (0.8-Ratio), and 7.5 and 6% (1.25-Ratio). The carbohydrates were ingested at 1.8 g/min and naturally 13C-enriched to permit evaluation of oxidation rate by mass spectrometry and indirect calorimetry. Mean exogenous carbohydrate oxidation rates were 1.04, 1.14, and 1.05 g/min (coefficient of variation 20%) in 0.5-, 0.8-, and 1.25-Ratios, respectively, representing likely small increases in 0.8-Ratio of 11% (90% confidence limits; ±4%) and 10% (±4%) relative to 0.5- and 1.25-Ratios, respectively. Comparisons of fat and total and endogenous carbohydrate oxidation rates between solutions were unclear. Relative to 0.5-Ratio, there were moderate improvements to peak power with 0.8- (3.6%; 99% confidence limits ± 3.5%) and 1.25-Ratio (3.0%; ±3.7%) but unclear with water (0.4%; ±4.4%). Increases in stomach fullness, abdominal cramping, and nausea were lowest with the 0.8- followed by the 1.25-Ratio solution. At high carbohydrate-ingestion rate, greater benefits to endurance performance may result from ingestion of 0.8- to 1.25-Ratio fructose-maltodextrin solutions. Small perceptible improvements in gut comfort favor the 0.8-Ratio and provide a clearer suggestion of mechanism than the relationship with exogenous carbohydrate oxidation.

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UK landfill methane emissions: Use of mobile plume measurements and carbon isotopic characterisation to reassess oxidation rates for open and closed sites

10.5194/egusphere-egu21-8192 ◽

2021 ◽

Author(s):

Semra Bakkaloglu ◽

Dave Lowry ◽

Rebecca Fisher ◽

James France ◽

Euan Nisbet

Keyword(s):

Methane Oxidation ◽

Mole Fraction ◽

Oxidation Rate ◽

Methane Emissions ◽

Isotopic Signature ◽

Oxidation Rates ◽

Landfill Cover ◽

Carbon Isotopic ◽

Landfill Sites ◽

The Impact

Biological methane oxidation in landfill cover material can be characterised using stable isotopes. Methane oxidation fraction is calculated from the carbon isotopic signature of emitted CH4, with enhanced microbial consumption of methane in the aerobic portion of the landfill cover indicated by a shift to less depleted isotopic values in the residual methane emitted to air. This study was performed at four southwest England landfill sites. Mobile mole fraction measurement at the four sites was coupled with Flexfoil bag sampling of air for high-precision isotope analysis. Gas well samples collected from the pipeline systems and downwind plume air samples were utilized to estimate methane oxidation rate for whole sites. This work was designed to assess the impact on carbon isotopic signature and oxidation rate as UK landfill practice and waste streams have changed in recent years.The landfill status such as closed and active, seasonal variation, cap stripping and site closure impact on landfill isotopic signature and oxidation rate were evaluated. The isotopic signature of 13C-CH4 values of emissions varied between -60 and -54&#8240;, with an averaged value of -57 +- 2&#8240; for methane from closed and active landfill sites. Methane emissions from older, closed landfill sites were typically more enriched in 13C than emissions from active sites. This study found that the isotopic signature of 13C-CH4 of fugitive methane did not show a seasonal trend, and there was no plume observed from a partial cap stripping process to assess changes in 13C-CH4&#160;&#160;isotopic signatures of emitted methane. Also, the closure of an active landfill cell caused a significant decrease in mole fraction of measured CH4, which was less depleted 13C in the emitted plume due to a higher oxidation rate. Methane oxidation, estimated from the isotope fractionation, ranged from 3 to 27%, with mean values of 7% and 15% for active and closed landfills, respectively. These results indicate that the oxidation rate is highly site specific.&#160;

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Effects of simulated high altitude on blood glucose levels during exercise in individuals with Type 1 Diabetes

The Journal of Clinical Endocrinology & Metabolism ◽

10.1210/clinem/dgab881 ◽

2021 ◽

Author(s):

Cory W Dugan ◽

Shane K Maloney ◽

Kristina J Abramoff ◽

Sohan S Panag ◽

Elizabeth A Davis ◽

...

Keyword(s):

High Altitude ◽

Acute Hypoxia ◽

Carbohydrate Oxidation ◽

Normoxic Condition ◽

Glucose Levels ◽

Oxidation Rates ◽

Blood Glucose Levels ◽

Simulated High Altitude ◽

The Impact

Abstract Context Current exercise guidelines for individuals with type 1 diabetes (T1D) do not consider the impact that high altitude may have on blood glucose levels (BGL) during exercise. Objective To investigate the effect of acute hypoxia (simulated high altitude) on BGL and carbohydrate oxidation rates during moderate intensity exercise in individuals with T1D. Methods Using a counterbalanced, repeated measures study design, 7 individuals with T1D completed two exercise sessions; normoxia and hypoxia (~4,200m simulated altitude). Participants cycled for 60min on an ergometer at 45% of their sea-level V̇O2peak, and then recovered for 60min. Before, during and after exercise, blood samples were taken to measure glucose, lactate and insulin levels. Respiratory gases were collected to measure carbohydrate oxidation rates. Results Early during exercise (<30min), there was no fall in BGL in either condition. After one hour of exercise and during recovery, BGL were significantly lower under the hypoxic condition compared to both pre-exercise levels (p=0.008) and the normoxic condition (p=0.027). Exercise in both conditions resulted in a significant rise in carbohydrate oxidation rates, which returned to baseline levels post-exercise. Before, during and after exercise, carbohydrate oxidation rates were higher under the hypoxic compared with the normoxic condition (p<0.001). Conclusions The greater decline in BGL during and after exercise performed under acute hypoxia suggests that exercise during acute exposure to high altitude may increase the risk of hypoglycemia in individuals with T1D. Future guidelines may have to consider the impact altitude has on exercise-mediated hypoglycemia.

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Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance

Journal of Applied Physiology ◽

10.1152/jappl.2000.89.6.2220 ◽

2000 ◽

Vol 89 (6) ◽

pp. 2220-2226 ◽

Cited By ~ 99

Author(s):

Mark A. Febbraio ◽

Alison Chiu ◽

Damien J. Angus ◽

Melissa J. Arkinstall ◽

John A. Hawley

Keyword(s):

Plasma Glucose ◽

Glucose Concentration ◽

Peak Power ◽

Glucose Oxidation ◽

Time Trial ◽

Peak Power Output ◽

Glucose Kinetics ◽

Carbohydrate Ingestion ◽

Total Fat ◽

And Performance

We investigated the effect of carbohydrate (CHO) ingestion before and during exercise and in combination on glucose kinetics, metabolism and performance in seven trained men, who cycled for 120 min (SS) at ∼63% of peak power output, followed by a 7 kJ/kg body wt time trial (TT). On four separate occasions, subjects received either a placebo beverage before and during SS (PP); placebo 30 min before and 2 g/kg body wt of CHO in a 6.4% CHO solution throughout SS (PC); 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and placebo throughout SS (CP); or 2 g/kg body wt of CHO in a 25.7% CHO beverage 30 min before and 2 g/kg of CHO in a 6.4% CHO solution throughout SS (CC). Ingestion of CC and CP markedly (>8 mM) increased plasma glucose concentration ([glucose]) compared with PP and PC (5 mM). However, plasma [glucose] fell rapidly at the onset of SS so that after 80 min it was similar (6 mM) between all treatments. After this time, plasma [glucose] declined in both PP and CP ( P < 0.05) but was well maintained in both CC and PC. Ingestion of CC and CP increased rates of glucose appearance (Ra) and disappearance (Rd) compared with PP and PC at the onset of, and early during, SS ( P < 0.05). However, late in SS, both glucose Ra and Rd were higher in CC and PC compared with other trials ( P < 0.05). Although calculated rates of glucose oxidation were different when comparing the four trials ( P < 0.05), total CHO oxidation and total fat oxidation were similar. Despite this, TT was improved in CC and PC compared with PP ( P < 0.05). We conclude that 1) preexercise ingestion of CHO improves performance only when CHO ingestion is maintained throughout exercise, and 2) ingestion of CHO during 120 min of cycling improves subsequent TT performance.

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Antagonistic interplay between pH and food resources affects copepod traits and performance in a year-round upwelling system

Scientific Reports ◽

10.1038/s41598-019-56621-6 ◽

2020 ◽

Vol 10 (1) ◽

Cited By ~ 1

Author(s):

Victor M. Aguilera ◽

Cristian A. Vargas ◽

Hans G. Dam

Keyword(s):

Ocean Acidification ◽

Egg Production ◽

Egg Size ◽

Ingestion Rate ◽

Food Resources ◽

Low Ph ◽

Phenotypic Traits ◽

Upwelling System ◽

And Performance ◽

The Impact

AbstractLinking pH/pCO2 natural variation to phenotypic traits and performance of foundational species provides essential information for assessing and predicting the impact of ocean acidification (OA) on marine ecosystems. Yet, evidence of such linkage for copepods, the most abundant metazoans in the oceans, remains scarce, particularly for naturally corrosive Eastern Boundary Upwelling systems (EBUs). This study assessed the relationship between pH levels and traits (body and egg size) and performance (ingestion rate (IR) and egg reproduction rate (EPR)) of the numerically dominant neritic copepod Acartia tonsa, in a year-round upwelling system of the northern (23° S) Humboldt EBUs. The study revealed decreases in chlorophyll (Chl) ingestion rate, egg production rate and egg size with decreasing pH as well as egg production efficiency, but the opposite for copepod body size. Further, ingestion rate increased hyperbolically with Chl, and saturated at ~1 µg Chl. L−1. Food resources categorized as high (H, >1 µg L−1) and low (L, <1 µg L−1) levels, and pH-values categorized as equivalent to present day (≤400 µatm pCO2, pH > 7.89) and future (>400 µatm pCO2, pH < 7.89) were used to compare our observations to values globally employed to experimentally test copepod sensitivity to OA. A comparison (PERMANOVA) test with Chl/pH (2*2) design showed that partially overlapping OA levels expected for the year 2100 in other ocean regions, low-pH conditions in this system negatively impacted traits and performance associated with copepod fitness. However, interacting antagonistically with pH, food resource (Chl) maintained copepod production in spite of low pH levels. Thus, the deleterious effects of ocean acidification are modulated by resource availability in this system.

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The Effects of Low- and High-Glycemic Index Sport Nutrition Bars on Metabolism and Performance in Recreational Soccer Players

Nutrients ◽

10.3390/nu12040982 ◽

2020 ◽

Vol 12 (4) ◽

pp. 982 ◽

Cited By ~ 2

Author(s):

Mojtaba Kaviani ◽

Philip D. Chilibeck ◽

Spencer Gall ◽

Jennifer Jochim ◽

Gordon A. Zello

Keyword(s):

Glycemic Index ◽

Oxidation Rate ◽

Sports Nutrition ◽

Carbohydrate Oxidation ◽

Sport Nutrition ◽

Double Blind ◽

Modest Improvement ◽

Soccer Match ◽

And Performance ◽

Low Glycemic Index

Consumption of low-glycemic index (GI) carbohydrates (CHO) may be superior to high-GI CHO before exercise by increasing fat oxidation and decreasing carbohydrate oxidation. We compared the effects of pre-exercise feeding of a low-GI lentil-based sports nutrition bar with a high-GI bar on metabolism and performance during a simulated soccer match. Using a randomized, double-blind, counterbalanced, crossover design, participants (n = 8) consumed 1.5 g/kg available CHO from a low-GI bar (GI = 45) or high-GI bar (GI = 101) two hours before a 90 min simulated soccer match, and 0.38 g/kg body mass during a 15 min half-time break. The test involved alternating 6 min intervals of paced jogging, running, walking, and sprinting, and 3 min intervals of soccer-specific skills (timed ball dribbling, agility running, heading, kicking accuracy). Carbohydrate oxidation rate was lower during the match after consuming the low-GI compared to high-GI bar (2.17 ± 0.6 vs. 2.72 ± 0.4 g/min; p < 0.05). Participants performed better during the low-GI versus high-GI bar condition on the agility test (5.7 ± 0.4 versus 6.1 ± 0.6 s; p < 0.01) and heading (i.e., jumping height 24.7 ± 4.3 versus 22.2 ± 4.5 cm; p < 0.01) late in the soccer match (72 min). A low-GI lentil-based sports nutrition bar provides a metabolic benefit (lower carbohydrate oxidation rate) and a modest improvement in agility running and jumping height (heading) late in the test.

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Ghrelin, insulin sensitivity and postprandial glucose disposal in overweight and obese children

Acta Endocrinologica ◽

10.1530/eje.1.02055 ◽

2006 ◽

Vol 154 (1) ◽

pp. 61-68 ◽

Cited By ~ 30

Author(s):

Claudio Maffeis ◽

Riccardo C Bonadonna ◽

Alessandro Consolaro ◽

Roberto Vettor ◽

Claudia Banzato ◽

...

Keyword(s):

Insulin Sensitivity ◽

Test Meal ◽

Oxidation Rate ◽

Standard Deviation Score ◽

Substrate Oxidation ◽

Carbohydrate Oxidation ◽

Glucose Disposal ◽

Obese Children ◽

Oxidation Rates ◽

Different Levels

Objective: To explore the changes of ghrelin circulating levels induced by a mixed meal and their relationship with postprandial substrate oxidation rates in overweight and obese children with different levels of insulin sensitivity. Methods: A group of ten boys (age 9–12 years) with different levels of overweight (standard deviation score of body mass index: 1.6–3.2) was recruited. Body composition was measured by dual-energy X-ray absorptiometry. Insulin sensitivity was assessed by a frequently sampled i.v. glucose tolerance test. Pre-prandial and postprandial (3 h) substrate oxidation was measured by indirect calorimetry. The energy content of the test meal (16% protein, 36% carbohydrate and 48% fat) was 40% of pre-prandial energy expenditure (kJ/day). Results: Pre-prandial serum concentration of total ghrelin was 701.4±66.9 pg/ml (S.E.M.). The test meal induced a rapid decrease in ghrelin levels and maximal decrease was 27.3±2.7% below baseline. Meal intake induced a progressive increase of the carbohydrate oxidation rate for 45 min after food ingestion, followed by a slow decrease without returning to pre-prandial values. Postprandial cumulative carbohydrate oxidation was 16.9±0.8 g/3 h. Insulin sensitivity and postprandial maximal decrease of ghrelin concentration showed a significant correlation (r = 0.803, P < 0.01). Moreover, the postprandial carbohydrate oxidation rate correlated with the area under the curve for both insulin (r = 0.673, P < 0.03) and ghrelin (r = −0.661, P < 0.04). Conclusions: A relevant association between postprandial insulin-mediated glucose metabolism and ghrelin secretion in children with different levels of overweight was found. It is possible that the maintenance of an adequate level of insulin sensitivity and glucose oxidation may affect appetite regulation by favoring a more efficient postprandial ghrelin reduction.

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Exogenous carbohydrate oxidation rates are elevated after combined ingestion of glucose and fructose during exercise in the heat

Journal of Applied Physiology ◽

10.1152/japplphysiol.00322.2005 ◽

2006 ◽

Vol 100 (3) ◽

pp. 807-816 ◽

Cited By ~ 67

Author(s):

Roy L. P. G. Jentjens ◽

Katie Underwood ◽

Juul Achten ◽

Kevin Currell ◽

Christopher H. Mann ◽

...

Keyword(s):

Oxygen Uptake ◽

Ambient Temperature ◽

Muscle Glycogen ◽

Power Output ◽

Maximal Oxygen Uptake ◽

Oxidation Rate ◽

Random Order ◽

Carbohydrate Oxidation ◽

Oxidation Rates ◽

Maximum Power Output

The first purpose of this study was to investigate whether a glucose (GLU) + fructose (FRUC) beverage would result in a higher exogenous carbohydrate (CHO) oxidation rate and a higher fluid availability during exercise in the heat compared with an isoenergetic GLU beverage. A second aim of the study was to examine whether ingestion of GLU at a rate of 1.5 g/min during exercise in the heat would lead to a reduced muscle glycogen oxidation rate compared with ingestion of water (WAT). Eight trained male cyclists (maximal oxygen uptake: 64 ± 1 ml·kg−1·min−1) cycled on three different occasions for 120 min at 50% maximum power output at an ambient temperature of 31.9 ± 0.1°C. Subjects received, in random order, a solution providing either 1.5 g/min of GLU, 1.0 g/min of GLU + 0.5 g/min of FRUC, or WAT. Exogenous CHO oxidation during the last hour of exercise was ∼36% higher ( P < 0.05) in GLU+FRUC compared with GLU, and peak oxidation rates were 1.14 ± 0.05 and 0.77 ± 0.08 g/min, respectively. Endogenous CHO oxidation was significantly lower ( P < 0.05) in GLU+FRUC compared with WAT. Muscle glycogen oxidation was not different after ingestion of GLU or WAT. Plasma deuterium enrichments were significantly higher ( P < 0.05) in WAT and GLU+FRUC compared with GLU. Furthermore, at 60 and 75 min of exercise, plasma deuterium enrichments were higher ( P < 0.05) in WAT compared with GLU+FRUC. Ingestion of GLU+FRUC during exercise in the heat resulted in higher exogenous CHO oxidation rates and fluid availability compared with ingestion of GLU and reduced endogenous CHO oxidation compared with ingestion of WAT.

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Preexercise Cycling Protocol Alters Pacing Behavior in Competitive Time Trials

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2019-0763 ◽

2020 ◽

Vol 15 (9) ◽

pp. 1303-1308

Author(s):

Marco J. Konings ◽

Florentina J. Hettinga

Keyword(s):

Power Output ◽

Repeated Measures ◽

Peak Power ◽

Perceived Exertion ◽

Time Trial ◽

Cycle Ergometer ◽

Peak Power Output ◽

Experimental Conditions ◽

And Performance ◽

The Impact

Purpose: The behavior of an opponent has been shown to alter pacing and performance. To advance our understanding of the impact of perceptual stimuli such as an opponent on pacing and performance, this study examined the effect of a preexercise cycling protocol on exercise regulation with and without an opponent. Methods: Twelve trained cyclists performed 4 experimental, self-paced 4-km time-trial conditions on an advanced cycle ergometer in a randomized, counterbalanced order. Participants started the time trial in rested state (RS) or performed a 10-min cycling protocol at 67% peak power output (CP) before the time trial. During the time trials, participants had to ride alone (NO) or against a virtual opponent (OP). The experimental conditions were (1) RS-NO, (2) RS-OP, (3) CP-NO, and (4) CP-OP. Repeated-measures analyses of variance (P < .05) were used to examine differences in pacing and performance in terms of power output. Results: A faster pace was adopted in the first kilometer during RS-OP (318 [72] W) compared with RS-NO (291 [81] W; P = .03), leading to an improved finishing time during RS-OP compared with RS-NO (P = .046). No differences in either pacing or performance were found between CP-NO and CP-OP. Conclusions: The evoked response by the opponent to adopt a faster initial pace in the 4-km time trial disappeared when cyclists had to perform a preceding cycling protocol. The outcomes of this study highlight that perceived exertion alters the responsiveness to perceptual stimuli of cyclists during competition.

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Effects of Preexercise Candy Bar Ingestion on Glycemic Response, Substrate Utilization, and Performance

International Journal of Sport Nutrition ◽

10.1123/ijsn.3.3.323 ◽

1993 ◽

Vol 3 (3) ◽

pp. 323-333 ◽

Cited By ~ 12

Author(s):

June C. Alberici ◽

Peter A. Farrell ◽

Penny M. Kris-Etherton ◽

Carol A. Shively

Keyword(s):

Athletic Performance ◽

Respiratory Exchange Ratio ◽

Substrate Utilization ◽

Carbohydrate Oxidation ◽

Time To Exhaustion ◽

Glycemic Response ◽

Total Carbohydrate ◽

Milk Chocolate ◽

Oxidation Rates ◽

And Performance

This study examined the effects of preexercise candy bar ingestion on glycemic response, substrate utilization, and performance ie 8 trained male cyclists. The cyclists randomly ingested oee large milk chocolate bar (1CB), two large milk chocolate bars (2CB), or a placebo (P) 30 min prior to a 90-min cycle ride at 70% VO2max followed by a 33-W increase every 2 min until exhaustion (~10 min). Glucose decreased after 15 min of exercise but returned to preexercise values by 30 min of exercise. Glucose concentration for 2CB was significantly higher than for P and 1CB at exhaustion, Insulin concentration increased in response to ICB and 2CB and returned to preexercise values within 15 min of exercise. No significant differences were noted for free fatty acid (FFA) concentrations, Jactate concentrations, respiratory exchange ratio, total carbohydrate oxidation, or estimated fat and carbohydrate oxidation rates. Time to exhaustion was similar among the groups. The results suggest that the transient lowering of blood glucose observed with preexercise milk chocolate bar ingestion 30 min prior to exercise may not cause major metabolic perturbations that impair athletic performance in trained athletes performing moderately intense cycle exercise.

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Effect of High-Fat, High-Carbohydrate, and High-Protein Meals on Metabolism and Performance during Endurance Cycling

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.12.3.318 ◽

2002 ◽

Vol 12 (3) ◽

pp. 318-335 ◽

Cited By ~ 19

Author(s):

David S. Rowlands ◽

Will G. Hopkins

Keyword(s):

Oxidation Rate ◽

Peak Power ◽

Time Trial ◽

Fat Oxidation ◽

High Protein ◽

High Fat ◽

High Carbohydrate ◽

Competitive Cyclists ◽

And Performance ◽

Meal Composition

The effect of pre-exercise meal composition on metabolism and performance in cycling were investigated in a crossover study. Twelve competitive cyclists ingested high-fat, high-carbohydrate, or high-protein meals 90 min before a weekly exercise test. The test consisted of a 1-hour pre-load at 55% peak power, five 10-min incremental loads from 55 to 82% peak power (to measure the peak fat-oxidation rate), and a 50-km time trial that included three 1-km and 4-km sprints. A carbohydrate supplement was ingested throughout the exercise. Relative to the high-protein and high-fat meals, the high-carbohydrate meal halved the peak fat-oxidation rate and reduced the fat oxidation across all workloads by a factor of 0.20 to 0.58 (p = .002–.0001). Reduced fat availability may have accounted for this reduction, as indicated by lower plasma fatty acid, lower glycerol, and higher pre-exercise insulin concentrations relative to the other meals (p = .04–.0001). In contrast, fat oxidation following the high-protein meal was similar to that following the high-fat meal. This similarity was linked to evidence suggesting greater lipolysis and plasma fat availability following high-protein relative to high-carbohydrate meals. Despite these substantial effects on metabolism, meal composition had no clear effect on sprint or 50-km performance.

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