Muscle glycogen oxidation during prolonged exercise measured with oral [13C]glucose: comparison with changes in muscle glycogen content

2007 ◽  
Vol 102 (5) ◽  
pp. 1773-1779 ◽  
Author(s):  
C. R. Harvey ◽  
R. Frew ◽  
D. Massicotte ◽  
F. Péronnet ◽  
N. J. Rehrer
Keyword(s):  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Vastus Lateralis ◽  
Energy Yield ◽  
Vastus Lateralis Muscle ◽  
Tracer Technique ◽  
Total Carbohydrate ◽  
Tracer Techniques

Plasma glucose and muscle glycogen oxidation during prolonged exercise [75-min at 48 and 76% maximal O2 uptake (V̇o2 max)] were measured in eight well-trained male subjects [V̇o2 max = 4.50 l/min (SD 0.63)] using a simplified tracer technique in which a small amount of glucose highly enriched in 13C was ingested: plasma glucose oxidation was computed from 13C/12C in plasma glucose (which was stable beginning at minute 30 and minute 15 during exercise at 48 and 76% V̇o2 max, respectively) and 13CO2 production, and muscle glycogen oxidation was estimated by subtracting plasma glucose oxidation from total carbohydrate oxidation. Consistent data from the literature suggest that this small dose of exogenous glucose does not modify muscle glycogen oxidation and has little effect, if any, on plasma glucose oxidation. The percent contributions of plasma glucose and muscle glycogen oxidation to the energy yield at 48% V̇o2 max [15.1% (SD 3.8) and 45.9% (SD 5.8)] and at 76% V̇o2 max [15.4% (SD 3.6) and 59.8% (SD 9.2)] were well in line with data previously reported for similar work loads and exercise durations using conventional tracer techniques. The significant reduction in glycogen concentration measured from pre- and postexercise vastus lateralis muscle biopsies paralleled muscle glycogen oxidation calculated using the tracer technique and was larger at 76% than at 48% V̇o2 max. However, the correlation coefficients between these two estimates of muscle glycogen utilization were not different from zero at each of the two work loads. The simplified tracer technique used in the present experiment appears to be a valid alternative approach to the traditional tracer techniques for computing plasma glucose and muscle glycogen oxidation during prolonged exercise.

Reversal of fatigue during prolonged exercise by carbohydrate infusion or ingestion

1987 ◽  
Vol 63 (6) ◽  
pp. 2388-2395 ◽  
Author(s):  
A. R. Coggan ◽  
E. F. Coyle
Keyword(s):  
Plasma Glucose ◽  
Prolonged Exercise ◽  
Respiratory Exchange Ratio ◽  
Vastus Lateralis ◽  
Exercise Bout ◽  
Glucose Infusion ◽  
Vastus Lateralis Muscle ◽  
Total Carbohydrate ◽  
Carbohydrate Ingestion ◽  
Placebo Trial

Seven cyclists exercised at 70% of maximal O2 uptake (VO2max) until fatigue (170 +/- 9 min) on three occasions, 1 wk apart. During these trials, plasma glucose declined from 5.0 +/- 0.1 to 3.1 +/- 0.1 mM (P less than 0.001) and respiratory exchange ratio (R) fell from 0.87 +/- 0.01 to 0.81 +/- 0.01 (P less than 0.001). After resting 20 min the subjects attempted to continue exercise either 1) after ingesting a placebo, 2) after ingesting glucose polymers (3 g/kg), or 3) when glucose was infused intravenously (“euglycemic clamp“). Placebo ingestion did not restore euglycemia or R. Plasma glucose increased (P less than 0.001) initially to approximately 5 mM and R rose (P less than 0.001) to approximately 0.83 with glucose infusion or carbohydrate ingestion. Plasma glucose and R then fell gradually to 3.9 +/- 0.3 mM and 0.81 +/- 0.01, respectively, after carbohydrate ingestion but were maintained at 5.1 +/- 0.1 mM and 0.83 +/- 0.01, respectively, by glucose infusion. Time to fatigue during this second exercise bout was significantly longer during the carbohydrate ingestion (26 +/- 4 min; P less than 0.05) or glucose infusion (43 +/- 5 min; P less than 0.01) trials compared with the placebo trial (10 +/- 1 min). Plasma insulin (approximately 10 microU/ml) and vastus lateralis muscle glycogen (approximately 40 mmol glucosyl U/kg) did not change during glucose infusion, with three-fourths of total carbohydrate oxidation during the second exercise bout accounted for by the euglycemic glucose infusion rate (1.13 +/- 0.08 g/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma glucose kinetics during exercise in subjects with high and low lactate thresholds

1992 ◽  
Vol 73 (5) ◽  
pp. 1873-1880 ◽  
Author(s):  
A. R. Coggan ◽  
W. M. Kohrt ◽  
R. J. Spina ◽  
J. P. Kirwan ◽  
D. M. Bier ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Plasma Glucose ◽  
Glucose Oxidation ◽  
Citrate Synthase ◽  
Metabolic Response ◽  
Vastus Lateralis ◽  
Cycle Ergometer ◽  
Vastus Lateralis Muscle ◽  
Respiratory Capacity ◽  
Group A

The purpose of this study was to test the hypothesis that the rate of plasma glucose oxidation during exercise is inversely related to muscle respiratory capacity. To this end, 14 subjects were studied: in 7 of these subjects, the blood lactate threshold (LT) occurred at a relatively high intensity [i.e., at 65 +/- 2% of peak cycle ergometer oxygen uptake (VO2 peak)], whereas in the other 7 subjects, LT occurred at a relatively low intensity (i.e., at 45 +/- 2% of VO2 peak). VO2peak did not differ between the two groups, but citrate synthase activity in the vastus lateralis muscle was 53% higher (P < 0.05) in the high LT group. A primed continuous infusion of [U-13C]glucose was used to quantify rates of glucose appearance (Ra), disappearance (Rd), and oxidation (R(ox)) during 90 min of exercise at 55% VO2peak. Although both absolute and relative rates of oxygen uptake during exercise were similar in the two groups, mean Ra and Rd were 17% lower (P < 0.001) in the high LT group, and mean R(ox) was 25% lower (21.0 +/- 2.6 vs. 27.9 +/- 2.6 mumol.min-1.kg-1; P < 0.001). The percentage of total energy derived from glucose oxidation was inversely related to muscle citrate synthase activity (r = -0.85; P < 0.01). These data support the concept that skeletal muscle respiratory capacity has a major role in determining the metabolic response to submaximal exercise.

Oxidation of an oral [13C]glucose load at rest and prolonged exercise in trained and sedentary subjects

1999 ◽  
Vol 86 (1) ◽  
pp. 52-60 ◽  
Author(s):  
Y. Burelle ◽  
F. Péronnet ◽  
S. Charpentier ◽  
C. Lavoie ◽  
C. Hillaire-Marcel ◽  
...  
Keyword(s):  
Oxygen Uptake ◽  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Glucose Load ◽  
Exogenous Glucose ◽  
Glycogen Stores ◽  
Male Subjects ◽  
Sedentary Subjects

The purpose of this study was to compare the oxidation of [13C]glucose (100 g) ingested at rest or during exercise in six trained (TS) and six sedentary (SS) male subjects. The oxidation of plasma glucose was also computed from the volume of13CO2and13C/12C in plasma glucose to compute the oxidation rate of glucose released from the liver and from glycogen stores in periphery (mainly muscle glycogen stores during exercise). At rest, oxidative disposal of both exogenous (8.3 ± 0.3 vs. 6.6 ± 0.8 g/h) and liver glucose (4.4 ± 0.5 vs. 2.6 ± 0.4 g/h) was higher in TS than in SS. This could contribute to the better glucose tolerance observed at rest in TS. During exercise, for the same absolute workload [140 ± 5 W: TS = 47 ± 2.5; SS = 68 ± 3 %maximal oxygen uptake (V˙o 2 max)], [13C]glucose oxidation was higher in TS than in SS (39.0 ± 2.6 vs. 33.6 ± 1.2 g/h), whereas both liver glucose (16.8 ± 2.4 vs. 24.0 ± 1.8 g/h) and muscle glycogen oxidation (36.0 ± 3.0 vs. 51.0 ± 5.4 g/h) were lower. For the same relative workload (68 ± 3% V˙o 2 max: TS = 3.13 ± 0.96; SS = 2.34 ± 0.60 l O2/min), exogenous glucose (44.4 ± 1.8 vs. 33.6 ± 1.2 g/h) and muscle glycogen oxidation (73.8 ± 7.2 vs. 51.0 ± 5.4 g/h) were higher in TS. However, despite a higher energy expenditure in TS, liver glucose oxidation was similar in both groups (22.2 ± 3.0 vs. 24.0 ± 1.8 g/h). Thus exogenous glucose oxidation was selectively favored in TS during exercise, reducing both liver glucose and muscle glycogen oxidation.

Effect of carbohydrate ingestion on metabolism during running and cycling

2001 ◽  
Vol 91 (5) ◽  
pp. 2125-2134 ◽  
Author(s):  
Melissa J. Arkinstall ◽  
Clinton R. Bruce ◽  
Vasilis Nikolopoulos ◽  
Andrew P. Garnham ◽  
John A. Hawley
Keyword(s):  
Body Mass ◽  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Lactate Threshold ◽  
Glucose Oxidation ◽  
Dry Mass ◽  
Carbohydrate Oxidation ◽  
Total Carbohydrate ◽  
Carbohydrate Ingestion ◽  
Glycogen Utilization

The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at individual lactate threshold using indirect calorimetry, U-14C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h; P < 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h; P < 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3%; P < 0.01) and cycling (36 ± 5 vs. 22 ± 3%; P < 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at individual lactate threshold.

Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate

1986 ◽  
Vol 61 (1) ◽  
pp. 165-172 ◽  
Author(s):  
E. F. Coyle ◽  
A. R. Coggan ◽  
M. K. Hemmert ◽  
J. L. Ivy
Keyword(s):  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Average Rate ◽  
Water Solution ◽  
Vastus Lateralis ◽  
Carbohydrate Oxidation ◽  
Strenuous Exercise ◽  
Vastus Lateralis Muscle ◽  
Glycogen Depletion ◽  
Glycogen Utilization

The purpose of this study was to determine whether the postponement of fatigue in subjects fed carbohydrate during prolonged strenuous exercise is associated with a slowing of muscle glycogen depletion. Seven endurance-trained cyclists exercised at 71 +/- 1% of maximal O2 consumption (VO2max), to fatigue, while ingesting a flavored water solution (i.e., placebo) during one trial and while ingesting a glucose polymer solution (i.e., 2.0 g/kg at 20 min and 0.4 g/kg every 20 min thereafter) during another trial. Fatigue during the placebo trial occurred after 3.02 +/- 0.19 h of exercise and was preceded by a decline (P less than 0.01) in plasma glucose to 2.5 +/- 0.5 mM and by a decline in the respiratory exchange ratio (i.e., R; from 0.85 to 0.80; P less than 0.05). Glycogen within the vastus lateralis muscle declined at an average rate of 51.5 +/- 5.4 mmol glucosyl units (GU) X kg-1 X h-1 during the first 2 h of exercise and at a slower rate (P less than 0.01) of 23.0 +/- 14.3 mmol GU X kg-1 X h-1 during the third and final hour. When fed carbohydrate, which maintained plasma glucose concentration (4.2–5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 +/- 0.33 h; P less than 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise performed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU X kg-1 X h-1; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue.

scholarly journals Oral [13C]glucose oxidation during prolonged exercise after high- and low-carbohydrate diets

1998 ◽  
Vol 85 (2) ◽  
pp. 723-730 ◽  
Author(s):  
F. Péronnet ◽  
N. Rhéaume ◽  
C. Lavoie ◽  
C. Hillaire-Marcel ◽  
D. Massicotte
Keyword(s):  
Oxygen Uptake ◽  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Maximal Oxygen Uptake ◽  
Oxidation Rate ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Exogenous Glucose ◽  
Low Carbohydrate ◽  
The Difference

The effect of a diet either high or low in carbohydrates (CHO) on exogenous 13C-labeled glucose oxidation (200 g) during exercise (ergocycle: 120 min at 64.0 ± 0.5% maximal oxygen uptake) was studied in six subjects. Between 40 and 80 min, exogenous glucose oxidation was significantly higher after the diet low in CHO (0.63 ± 0.05 vs. 0.52 ± 0.04 g/min), but this difference disappeared between 80 and 120 min (0.71 ± 0.03 vs. 0.69 ± 0.04 g/min). The oxidation rate of plasma glucose, computed from the volume of13CO2produced the13C-to-12C ratio in plasma glucose at 80 min, and of glucose released from the liver, computed from the difference between plasma glucose and exogenous glucose oxidation, was higher after the diet low in CHO (1.68 ± 0.26 vs. 1.41 ± 0.17 and 1.02 ± 0.20 vs. 0.81 ± 0.14 g/min, respectively). In contrast the oxidation rate of glucose plus lactate from muscle glycogen (computed from the difference between total CHO oxidation and plasma glucose oxidation) was lower (0.31 ± 0.35 vs. 1.59 ± 0.20 g/min). After a diet low in CHO, the oxidation of exogenous glucose and of glucose released from the liver is increased and partly compensates for the reduction in muscle glycogen availability and oxidation.

Muscle glycogen availability and temperature regulation in humans

1989 ◽  
Vol 66 (1) ◽  
pp. 72-78 ◽  
Author(s):  
L. Martineau ◽  
I. Jacobs
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Temperature Regulation ◽  
Vastus Lateralis ◽  
Water Immersion ◽  
Vastus Lateralis Muscle ◽  
Glycogen Concentration ◽  
Exercise Regimen ◽  
Before And After ◽  
Muscle Groups

The effects of intramuscular glycogen availability on human temperature regulation were studied in eight seminude subjects immersed in 18 degrees C water for 90 min or until rectal temperature (Tre) decreased to 35.5 degrees C. Each subject was immersed three times over a 3-wk period. Each immersion followed 2.5 days of a specific dietary and/or exercise regimen designed to elicit low (L), normal (N), or high (H) glycogen levels in large skeletal muscle groups. Muscle glycogen concentration was determined in biopsies taken from the vastus lateralis muscle before and after each immersion. Intramuscular glycogen concentration before the immersion was significantly different among the L, N, and H trials (P less than 0.01), averaging 247 +/- 15, 406 +/- 23, and 548 +/- 42 (SE) mmol glucose units.kg dry muscle-1, respectively. The calculated metabolic heat production during the first 30 min of immersion was significantly lower during L compared with N or H (P less than 0.05). The rate at which Tre decreased was more rapid during the L immersion than either N or H (P less than 0.05), and the time during the immersion at which Tre first began to decrease also appeared sooner during L than N or H. The results suggest that low skeletal muscle glycogen levels are associated with more rapid body cooling during water immersion in humans. Higher than normal muscle glycogen levels, however, do not increase cold tolerance.

Heat stress increases muscle glycogen use but reduces the oxidation of ingested carbohydrates during exercise

2002 ◽  
Vol 92 (4) ◽  
pp. 1562-1572 ◽  
Author(s):  
Roy L. P. G. Jentjens ◽  
Anton J. M. Wagenmakers ◽  
Asker E. Jeukendrup
Keyword(s):  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Oxidation Rate ◽  
Glucose Oxidation ◽  
Statistical Significance ◽  
Maximal Oxygen Consumption ◽  
Exogenous Glucose ◽  
Cool Environment ◽  
Lower Plasma Glucose ◽  
Glucose Plasma

The aim of the present study was to test the hypothesis that the oxidation rate of ingested carbohydrate (CHO) is impaired during exercise in the heat compared with a cool environment. Nine trained cyclists (maximal oxygen consumption 65 ± 1 ml · kg body wt−1 · min−1) exercised on two different occasions for 90 min at 55% maximum power ouptput at an ambient temperature of either 16.4 ± 0.2°C (cool trial) or 35.4 ± 0.1°C (heat trial). Subjects received 8% glucose solutions that were enriched with [U-13C]glucose for measurements of exogenous glucose, plasma glucose, liver-derived glucose and muscle glycogen oxidation. Exogenous glucose oxidation during the final 30 min of exercise was significantly ( P < 0.05) lower in the heat compared with the cool trial (0.76 ± 0.06 vs. 0.84 ± 0.05 g/min). Muscle glycogen oxidation during the final 30 min of exercise was increased by 25% in the heat (2.07 ± 0.16 vs. 1.66 ± 0.09 g/min; P < 0.05), and liver-derived glucose oxidation was not different. There was a trend toward a higher total CHO oxidation and a lower plasma glucose oxidation in the heat although this did not reach statistical significance ( P = 0.087 and P = 0.082, respectively). These results demonstrate that the oxidation rate of ingested CHO is reduced and muscle glycogen utilization is increased during exercise in the heat compared with a cool environment.

Human Skeletal Muscle Glycogen Branching Enzyme Activities with Exercise and Training

1974 ◽  
Vol 52 (1) ◽  
pp. 119-122 ◽  
Author(s):  
A. W. Taylor ◽  
J. Stothart ◽  
M. A. Booth ◽  
R. Thayer ◽  
S. Rao
Keyword(s):  
Skeletal Muscle ◽  
Muscle Glycogen ◽  
Enzyme Activities ◽  
Vastus Lateralis ◽  
Submaximal Exercise ◽  
Relative Fitness ◽  
Vastus Lateralis Muscle ◽  
Branching Enzyme ◽  
Skeletal Muscle Glycogen ◽  
Glycogen Branching Enzyme

Sixteen healthy male subjects classified as sedentary (8) or active (8), exercised to exhaustion on a bicycle ergometer at a load requiring 70% of their maximal aerobic capacity. Biopsy samples of the vastus lateralis muscle were taken at rest and at the time of fatigue. A 12 week training program increased skeletal muscle glycogen content and branching enzyme activities twofold. The exhaustive submaximal exercise reduced the glycogen levels of the trained group to values similar to the fatigue levels of the non-trained subjects. Skeletal muscle glycogen branching enzyme activities decreased with submaximal exercise to fatigue in all groups. Maximal exercise to fatigue resulted in small increases in the activities of the enzyme. The results of the present study and a previous study (Taylor et al. 1972. Can. J. Physiol. Pharmacol. 50, 411–415) indicate that the activities of the glycogen synthesizing enzymes are highly correlated with the skeletal muscle resting glycogen concentration and the relative fitness of the subjects.

Oxidation of [13C]glycerol ingested along with glucose during prolonged exercise

2001 ◽  
Vol 90 (5) ◽  
pp. 1685-1690 ◽  
Author(s):  
Y. Burelle ◽  
D. Massicotte ◽  
M. Lussier ◽  
C. Lavoie ◽  
C. Hillaire-Marcel ◽  
...  
Keyword(s):  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Energy Yield ◽  
Direct Oxidation ◽  
Energy Potential ◽  
Peripheral Tissues ◽  
Exogenous Glucose ◽  
Placebo Trial ◽  
Total Glucose ◽  
Effect Of Glucose

The respective oxidation of glycerol and glucose (0.36 g/kg each) ingested simultaneously immediately before exercise (120 min at 68 ± 2% maximal oxygen uptake) was measured in six subjects using 13C labeling. Indirect respiratory calorimetry corrected for protein and glycerol oxidation was used to evaluate the effect of glucose + glycerol ingestion on the oxidation of glucose and fat. Over the last 80 min of exercise, 10.0 ± 0.8 g of exogenous glycerol were oxidized (43% of the load), while exogenous glucose oxidation was 21% higher (12.1 ± 0.7 g or 52% of the load). However, because the energy potential of glycerol is 18% higher than that of glucose (4.57 vs. 3.87 kcal/g), the contribution of both exogenous substrates to the energy yield was similar (4.0–4.1%). Total glucose and fat oxidation were similar in the placebo (144.4 ± 13.0 and 60.5 ± 4.2 g, respectively) and the glucose + glycerol (135.2 ± 12.0 and 59.4 ± 6.5 g, respectively) trials, whereas endogenous glucose oxidation was significantly lower than in the placebo trial (123.7 ± 11.7 vs. 144.4 ± 13.0 g). These results indicate that exogenous glycerol can be oxidized during prolonged exercise, presumably following conversion into glucose in the liver, although direct oxidation in peripheral tissues cannot be ruled out.

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