Effects of carbohydrate ingestion 15 min before exercise on endurance running capacity

2008 ◽  
Vol 33 (3) ◽  
pp. 441-449 ◽  
Author(s):  
Savvas P. Tokmakidis ◽  
Ioannis A. Karamanolis
Keyword(s):  
Plasma Insulin ◽  
Prolonged Exercise ◽  
Serum Glucose ◽  
Time To Exhaustion ◽  
Endurance Running ◽  
Carbohydrate Source ◽  
Carbohydrate Ingestion ◽  
Oxidation Rates ◽  
Glucose Ingestion ◽  
Serum Glycerol

This study examined the effects of pre-exercise carbohydrate ingestion on exercise metabolism and endurance running capacity. Eleven active subjects (VO2 max 49.0 ± 1.7 mL·kg–1·min–1, mean ± SE) performed two exercise trials 15 min after ingesting glucose (G; 1 g·kg body mass–1) and placebo (CON). Each subject ran on a level treadmill for 5 min at 60%, 45 min at 70%, and then at 80% of VO2 max until exhaustion. Serum glucose and plasma insulin reached their peak concentrations (p < 0.01) 15 min after glucose ingestion and declined at the onset of exercise. Serum glycerol concentrations were lower (p < 0.01) in the G trial than in the CON trial after 30 min of exercise to exhaustion. In addition, after 45 min of exercise to exhaustion, the levels of free fatty acids were lower in G than in CON (p < 0.05). No differences were observed in carbohydrate oxidation rates during exercise between treatments (G, 2.53 ± 0.08 g·min–1; CON, 2.40 ± 0.09 g·min–1). Time to exhaustion was 12.8% longer in G (p < 0.01) than in CON. These results suggest that glucose ingestion 15 min before prolonged exercise provides an additional carbohydrate source to the exercising muscle, thus improving endurance running capacity.

Carbohydrate ingestion before exercise: comparison of glucose, fructose, and sweet placebo

1981 ◽  
Vol 51 (4) ◽  
pp. 783-787 ◽  
Author(s):  
V. A. Koivisto ◽  
S. L. Karonen ◽  
E. A. Nikkila
Keyword(s):  
Plasma Glucose ◽  
Plasma Insulin ◽  
Cycle Ergometer ◽  
Vo2 Max ◽  
Vigorous Exercise ◽  
Carbohydrate Ingestion ◽  
Rapid Fall ◽  
Ergometer Exercise ◽  
Glucose Ingestion ◽  
Response To Exercise

To examine the effect of various carbohydrates on the metabolic and hormonal response to exercise, 75 g glucose, fructose, or placebo were given to nine well-trained males (VO2 max 60 +/- 1 ml . kg-1 . min-1) 45 min before cycle ergometer exercise performed at 75% VO2 max for 30 min. After glucose ingestion, the rise in plasma glucose was 3-fold (P less than 0.005) in plasma insulin 2.5-fold (P less than 0.01) greater than after fructose. During exercise, after glucose administration plasma glucose fell from 5.3 +/- 0.3 to 2.5 +/- 0.2 mmol/l (P less than 0.001) and after fructose from 4.5 +/- 0.1 to 3.9 +/- 0.3 mmol/l (P less than 0.05). The fall in plasma glucose was closely related to the preexercise levels of plasma insulin (r = 0.82, P less than 0.001) and glucose (r = 0.81, P less than 0.001). Both glucose and fructose ingestion decreased the FFA levels by 40–50% (P less than 0.005) and during exercise they remained 30–40% lower after carbohydrate than placebo administration (P less than 0.02). This study suggests that glucose ingestion prior to exercise results in hypoglycemia during vigorous exercise, this rapid fall in plasma glucose is mediated, at least in part, by hyperinsulinemia, and fructose ingestion is associated with a modest rise in plasma insulin and does not result in hypoglycemia during exercise.

scholarly journals Improved Recovery from Prolonged Exercise Following the Consumption of Low Glycemic Index Carbohydrate Meals

2005 ◽  
Vol 15 (4) ◽  
pp. 333-349 ◽  
Author(s):  
Emma Stevenson ◽  
Clyde Williams ◽  
Gareth McComb ◽  
Christopher Oram
Keyword(s):  
Fatty Acid ◽  
Free Fatty Acid ◽  
Glycemic Index ◽  
Prolonged Exercise ◽  
Fat Oxidation ◽  
Time To Exhaustion ◽  
Endurance Capacity ◽  
Post Exercise ◽  
Oxidation Rates ◽  
Low Glycemic Index

This study examined the effects of the glycemic index (GI) of post-exercise carbohydrate (CHO) intake on endurance capacity the following day. Nine active males participated in 2 trials. On day 1, subjects ran for 90 min at 70% VO2max (R1). Thereafter, they were supplied with either a high GI (HGI) or low GI (LGI) CHO diet which provided 8 g CHO/kg body mass (BM). On day 2, after an overnight fast, subjects ran to exhaustion at 70% VO2max (R2). Time to exhaustion during R2 was longer in the LGI trial (108.9 ± 7.4 min) than in the HGI trial (96.9 ± 4.8 min) (P < 0.05). Fat oxidation rates and free fatty acid concentrations were higher in the LGI trial than the HGI trial (P < 0.05). The results suggest that the increased endurance capacity was largely a consequence of the increased fat oxidation following the LGI recovery diet.

Comparison of thermogenic effect of fructose and glucose in normal humans

1986 ◽  
Vol 250 (6) ◽  
pp. E718-E724 ◽  
Author(s):  
L. Tappy ◽  
J. P. Randin ◽  
J. P. Felber ◽  
R. Chiolero ◽  
D. C. Simonson ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Lipid Oxidation ◽  
Plasma Insulin ◽  
Carbohydrate Oxidation ◽  
Insulin Concentration ◽  
Adrenergic Blockade ◽  
Plasma Insulin Concentration ◽  
Carbohydrate Ingestion ◽  
Glucose Ingestion ◽  
Adrenergic Nervous System

After nutrient ingestion there is an increase in energy expenditure that has been referred to as dietary-induced thermogenesis. In the present study we have employed indirect calorimetry to compare the increment in energy expenditure after the ingestion of 75 g of glucose or fructose in 17 healthy volunteers. During the 4 h after glucose ingestion the plasma insulin concentration increased by 33 +/- 4 microU/ml and this was associated with a significant increase in carbohydrate oxidation and decrement in lipid oxidation. Energy expenditure increased by 0.08 +/- 0.01 kcal/min. When fructose was ingested, the plasma insulin concentration increased by only 8 +/- 2 microU/ml vs. glucose. Nonetheless, the increments in carbohydrate oxidation and decrement in lipid oxidation were significantly greater than with glucose. The increment in energy expenditure was also greater with fructose. When the mean increment in plasma insulin concentration after fructose was reproduced using the insulin clamp technique, the increase in carbohydrate oxidation and decrement in lipid oxidation were markedly reduced compared with the fructose-ingestion study; energy expenditure failed to increase above basal levels. To examine the role of the adrenergic nervous system in fructose-induced thermogenesis, fructose ingestion was also performed during beta-adrenergic blockade with propranolol. The increase in energy expenditure during fructose plus propranolol was lower than with fructose ingestion alone. These results indicate that the stimulation of thermogenesis after carbohydrate ingestion is related to an augmentation of cellular metabolism and is not dependent on an increase in the plasma insulin concentration per se.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycogen depletion during prolonged exercise: influence of glucose, fructose, or placebo

1985 ◽  
Vol 58 (3) ◽  
pp. 731-737 ◽  
Author(s):  
V. A. Koivisto ◽  
M. Harkonen ◽  
S. L. Karonen ◽  
P. H. Groop ◽  
R. Elovainio ◽  
...  
Keyword(s):  
Plasma Glucose ◽  
Prolonged Exercise ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Glycogen Depletion ◽  
Serum Free Fatty Acid ◽  
Carbohydrate Ingestion ◽  
Ergometer Exercise ◽  
Glucose Ingestion

We examined the influence of various carbohydrates of fuel homeostasis and glycogen utilization during prolonged exercise. Seventy-five grams of glucose, fructose, or placebo were given orally to eight healthy males 45 min before ergometer exercise performed for 2 h at 55% of maximal aerobic power (VO2max). After glucose ingestion, the rises in plasma glucose (P less than 0.01) and insulin (P less than 0.001) were 2.4- and 5.8-fold greater than when fructose was consumed. After 30 min of exercise following glucose ingestion, the plasma glucose concentration had declined to a nadir of 3.9 +/- 0.3 mmol/l, and plasma insulin had returned to basal levels. The fall in plasma glucose was closely related to the preexercise glucose (r = 0.98, P less than 0.001) and insulin (r = 0.66, P less than 0.05) levels. The rate of endogenous glucose production and utilization rose similarly by 2.8-fold during exercise in fructose group and were 10–15% higher than in placebo group (P less than 0.05). Serum free fatty acid levels were 1.5- to 2-fold higher (P less than 0.01) after placebo than carbohydrate ingestion. Muscle glycogen concentration in the quadriceps femoris fell in all three groups by 60–65% (P less than 0.001) during exercise. These data indicate that fructose ingestion, though causing smaller perturbations in plasma glucose, insulin, and gastrointestinal polypeptide (GIP) levels than glucose ingestion, was no more effective than glucose or placebo in sparing glycogen during a long-term exercise.

Use of 13C substrates for metabolic studies in exercise: methodological considerations

1990 ◽  
Vol 69 (3) ◽  
pp. 1047-1052 ◽  
Author(s):  
F. Peronnet ◽  
D. Massicotte ◽  
G. Brisson ◽  
C. Hillaire-Marcel
Keyword(s):  
Isotopic Composition ◽  
Prolonged Exercise ◽  
Substrate Oxidation ◽  
O2 Uptake ◽  
Common Mistake ◽  
Exogenous Glucose ◽  
Exogenous Substrate ◽  
Glucose Ingestion ◽  
Endogenous Substrates ◽  
Methodological Considerations

The purpose of this study is to outline a common mistake made when the rate of oxidation of exogenous substrates during prolonged exercise is computed using 13C naturally labeled substrates. The equation proposed and commonly used in the computation does not take into account that exercise and/or exogenous substrate ingestion modifies the composition of the mixture of endogenous substrates oxidized and, consequently, the isotopic composition of CO2 arising from oxidation of endogenous substrates. The recovery of 13C and the amount of exogenous substrate oxidized are thus overestimated. An adequate procedure for the computation of exogenous substrate oxidation taking into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates is suggested. Results from a pilot experiment (4 subjects) using this procedure indicate that over 2 h of exercise (66% of maximal O2 uptake), with ingestion of 60 g of glucose, 39 +/- 4 g of glucose were oxidized. Estimates made without taking into account changes in isotopic composition of CO2 arising from oxidation of endogenous substrates range between 70 +/- 8 and 44 +/- 3 g depending on 1) the isotopic composition of exogenous glucose and 2) the isotopic composition of expired CO2 taken as reference (rest or exercise without glucose ingestion). These observations suggest that results from previous studies of exogenous substrate oxidation during exercise using 13C labeling should be used with caution.

Effect of carbohydrate ingestion on exercise-induced alterations in metabolic gene expression

2005 ◽  
Vol 99 (4) ◽  
pp. 1359-1363 ◽  
Author(s):  
Laura J. Cluberton ◽  
Sean L. McGee ◽  
Robyn M. Murphy ◽  
Mark Hargreaves
Keyword(s):  
Gene Expression ◽  
Oxygen Uptake ◽  
Pyruvate Dehydrogenase Kinase ◽  
Mrna Levels ◽  
Carbohydrate Ingestion ◽  
Pulmonary Oxygen Uptake ◽  
Metabolic Gene ◽  
Metabolic Gene Expression ◽  
Glucose Ingestion ◽  
Exercise Induced

Skeletal muscle possesses a high degree of plasticity and can adapt to both the physical and metabolic challenges that it faces. An acute bout of exercise is sufficient to induce the expression of a variety of metabolic genes, such as GLUT4, pyruvate dehydrogenase kinase 4 (PDK-4), uncoupling protein-3 (UCP3), and peroxisome proliferator-activated receptor-γ coactivator 1 (PGC-1). Reducing muscle glycogen levels before exercise potentiates the effect of exercise on many genes. Similarly, altered substrate availability induces transcription of many of these genes. The purpose of this study was to determine whether glucose ingestion attenuates the exercise-induced increase in a variety of exercise-responsive genes. Six male subjects (28 ± 7 yr; 83 ± 3 kg; peak pulmonary oxygen uptake = 46 ± 6 ml·kg−1·min−1) performed 60 min of cycling at 74 ± 2% of peak pulmonary oxygen uptake on two separate occasions. On one occasion, subjects ingested a 6% carbohydrate drink. On the other occasion, subjects ingested an equal volume of a sweet placebo. Muscle samples were obtained from vastus lateralis at rest, immediately after exercise, and 3 h after exercise. PDK-4, UCP3, PGC-1, and GLUT4 mRNA levels were measured on these samples using real-time RT-PCR. Glucose ingestion attenuated ( P < 0.05) the exercise-induced increase in PDK-4 and UCP3 mRNA. A similar trend ( P = 0.09) was observed for GLUT4 mRNA. In contrast, PGC-1 mRNA increased following exercise to the same extent in both conditions. These data suggest that glucose availability can modulate the effect of exercise on metabolic gene expression.

scholarly journals Glucose ingestion and substrate utilization during exercise in boys with IDDM

2000 ◽  
Vol 88 (4) ◽  
pp. 1239-1246 ◽  
Author(s):  
M. C. Riddell ◽  
O. Bar-Or ◽  
M. Hollidge-Horvat ◽  
H. P. Schwarcz ◽  
G. J. F. Heigenhauser
Keyword(s):  
Energy Supply ◽  
Plasma Insulin ◽  
Insulin Dependent Diabetes Mellitus ◽  
Dependent Diabetes Mellitus ◽  
Glucose Ingestion ◽  
Insulin Dependent ◽  
Plasma Insulin Levels ◽  
Endogenous Glucose ◽  
Total Fat ◽  
Total Glucose

This study was intended to compare exogenous [13C]glucose (Gluexo) oxidation in boys with insulin-dependent diabetes mellitus (IDDM) and healthy boys of similar age, weight, and maximal O2 uptake. In a control trial with water intake (CT) and in a 13C-enriched glucose trial (GT), subjects cycled for 60 min (58.8 ± 0.9% maximal O2 uptake) while the utilization of total glucose, total fat, and Gluexo was assessed. In CT, total glucose was 84.7 ± 9.2 vs. 91.3 ± 6.6 g/60 min (not significantly different) and total fat was 13.3 ± 2.2 vs. 11.1 ± 1.7 g/60 min (not significantly different) in IDDM vs. healthy boys, respectively. In GT, Gluexo was 10.4 ± 1.7 vs. 14.8 ± 1.1 g/60 min, corresponding to 9.0 ± 1.0 vs. 12.4 ± 0.5% of the total energy supply in IDDM and healthy boys, respectively ( P < 0.05). Endogenous glucose was spared in both groups by 12.6 ± 3.5% ( P < 0.05). Blood glucose and plasma insulin concentrations were two- to threefold higher in IDDM vs. healthy boys in both trials. In conclusion, Gluexo is impaired in exercising boys with IDDM, even when plasma insulin levels are elevated.

Effect of menstrual cycle phase on carbohydrate supplementation during prolonged exercise to fatigue

2000 ◽  
Vol 88 (2) ◽  
pp. 690-697 ◽  
Author(s):  
Stephen P. Bailey ◽  
Cristine M. Zacher ◽  
Karen D. Mittleman
Keyword(s):  
Fatty Acids ◽  
Menstrual Cycle ◽  
Prolonged Exercise ◽  
Cycle Phase ◽  
Time To Exhaustion ◽  
Menstrual Cycle Phase ◽  
Exercise Time ◽  
Carbohydrate Supplementation ◽  
Plasma Tyrosine ◽  
Placebo Drink

The effects of menstrual cycle phase and carbohydrate (CHO) supplementation were investigated during prolonged exercise. Nine healthy, moderately trained women cycled at 70% peak O2 consumption until exhaustion. Two trials were completed during the follicular (Fol) and luteal (Lut) phases of the menstrual cycle. Subjects consumed 0.6 g CHO ⋅ kg body wt− 1 ⋅ h− 1(5 ml/kg of a 6% CHO solution every 30 min beginning at min 30 of exercise) or a placebo drink (Pl) during exercise. Time to exhaustion during CHO increased from Pl values ( P < 0.05) by 14.4 ± 8.5 (Fol) and 11.4 ± 7.1% (Lut); no differences were observed between menstrual cycle phases. CHO attenuated ( P < 0.05) the decrease in plasma glucose and insulin and the increase in plasma free fatty acids, tryptophan, epinephrine, and cortisol observed during Pl for both phases. Plasma alanine, glutamine, proline, and isoleucine were lower ( P < 0.05) in Lut than in Fol phase. CHO resulted in lower ( P < 0.05) plasma tyrosine, valine, leucine, isoleucine, and phenylalanine. These results indicate that the menstrual cycle phase does not alter the effects of CHO supplementation on performance and plasma levels of related substrates during prolonged exercise.

Muscle metabolism during prolonged exercise in humans: influence of carbohydrate availability

1999 ◽  
Vol 87 (3) ◽  
pp. 1083-1086 ◽  
Author(s):  
G. McConell ◽  
R. J. Snow ◽  
J. Proietto ◽  
M. Hargreaves
Keyword(s):  
Oxygen Uptake ◽  
Vastus Lateralis ◽  
Time To Exhaustion ◽  
Endurance Capacity ◽  
Vastus Lateralis Muscle ◽  
Double Blind ◽  
Muscle Lactate ◽  
Carbohydrate Ingestion ◽  
Inosine Monophosphate ◽  
Muscle Energy

Eight endurance-trained men cycled to volitional exhaustion at 69 ± 1% peak oxygen uptake on two occasions to examine the effect of carbohydrate supplementation during exercise on muscle energy metabolism. Subjects ingested an 8% carbohydrate solution (CHO trial) or a sweet placebo (Con trial) in a double-blind, randomized order, with vastus lateralis muscle biopsies ( n = 7) obtained before and immediately after exercise. No differences in oxygen uptake, heart rate, or respiratory exchange ratio during exercise were observed between the trials. Exercise time to exhaustion was increased by ∼30% when carbohydrate was ingested [199 ± 21 vs. 152 ± 9 (SE) min, P < 0.05]. Plasma glucose and insulin levels during exercise were higher and plasma free fatty acids lower in the CHO trial. No differences between trials were observed in the decreases in muscle glycogen and phosphocreatine or the increases in muscle lactate due to exercise. Muscle ATP levels were not altered by exercise in either trial. There was a small but significant increase in muscle inosine monophosphate levels at the point of exhaustion in both trials, and despite the subjects in CHO trial cycling 47 min longer, their muscle inosine monophosphate level was significantly lower than in the Con trial (CHO: 0.16 ± 0.08, Con: 0.23 ± 0.09 mmol/kg dry muscle). These data suggest that carbohydrate ingestion may increase endurance capacity, at least in part, by improving muscle energy balance.

Substrate metabolism when subjects are fed carbohydrate during exercise

1999 ◽  
Vol 276 (5) ◽  
pp. E828-E835 ◽  
Author(s):  
Jeffrey F. Horowitz ◽  
Ricardo Mora-Rodriguez ◽  
Lauri O. Byerley ◽  
Edward F. Coyle
Keyword(s):  
Plasma Insulin ◽  
Fat Oxidation ◽  
Insulin Concentration ◽  
Peak Oxygen Consumption ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Plasma Insulin Concentration ◽  
Carbohydrate Ingestion ◽  
Low Intensity ◽  
Low Intensity Exercise

This study determined the effect of carbohydrate ingestion during exercise on the lipolytic rate, glucose disappearance from plasma (Rd Glc), and fat oxidation. Six moderately trained men cycled for 2 h on four separate occasions. During two trials, they were fed a high-glycemic carbohydrate meal during exercise at 30 min (0.8 g/kg), 60 min (0.4 g/kg), and 90 min (0.4 g/kg); once during low-intensity exercise [25% peak oxygen consumption (V˙o 2 peak)] and once during moderate-intensity exercise (68%V˙o 2 peak). During two additional trials, the subjects remained fasted (12–14 h) throughout exercise at each intensity. After 55 min of low-intensity exercise in fed subjects, hyperglycemia (30% increase) and a threefold elevation in plasma insulin concentration ( P < 0.05) were associated with a 22% suppression of lipolysis compared with when subjects were fasted (5.2 ± 0.5 vs. 6.7 ± 1.2 μmol ⋅ kg−1 ⋅ min−1, P < 0.05), but fat oxidation was not different from fasted levels at this time. Fat oxidation when subjects were fed carbohydrate was not reduced below fasting levels until 80–90 min of exercise, and lipolysis was in excess of fat oxidation at this time. The reduction in fat oxidation corresponded in time with the increase in Rd Glc. During moderate-intensity exercise, the very small elevation in plasma insulin concentration (∼3 μU/ml; P < 0.05) during the second hour of exercise when subjects were fed vs. when they were fasted slightly attenuated lipolysis ( P < 0.05) but did not increase Rd Glc or suppress fat oxidation. These findings indicate that despite a suppression of lipolysis after carbohydrate ingestion during exercise, the lipolytic rate remained in excess and thus did not limit fat oxidation. Under these conditions, a reduction in fat oxidation was associated in time with an increase in glucose uptake.

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