Effect of physical training on utilization of a glucose load given orally during exercise

1984 ◽  
Vol 246 (5) ◽  
pp. E412-E417 ◽  
Author(s):  
G. Krzentowski ◽  
F. Pirnay ◽  
A. S. Luyckx ◽  
M. Lacroix ◽  
F. Mosora ◽  
...  
Keyword(s):  
Lipid Oxidation ◽  
Physical Training ◽  
Glucose Oxidation ◽  
Exercise Bout ◽  
Moderate Intensity ◽  
Glucose Load ◽  
Total Carbohydrate ◽  
Oxidation Rates ◽  
Exogenous Glucose ◽  
Glucose Ingestion

The effect of a 6-wk training period on the oxidation of a 100-g glucose load given orally during exercise was investigated in six healthy male volunteers. The subjects were submitted before and 24 h after the training program to a 105-min exercise bout (performed at about 40% of the pretraining VO2max) followed by a 90-min resting period. Naturally labeled [13C]glucose was given 15 min after the beginning of exercise. Exogenous glucose oxidation was derived from 13CO2 measurements in expired air, and total glucose and lipid oxidation were evaluated by indirect calorimetry. Training (60-min bicycling 5 days a week at 30-40% VO2max) resulted in a 29% increase in VO2max. During the 15 min of exercise that preceded glucose ingestion, the rate of total carbohydrate oxidation was slightly decreased after training, whereas the rate of lipid oxidation was slightly increased. Training did not affect the response of blood glucose, plasma insulin, or plasma free fatty acids to the glucose ingested during exercise; in contrast, the circulating levels of epinephrine, glycerol, and lactate were significantly reduced after training. Substrate utilization measurements revealed similar oxidation rates of carbohydrates (106.9 +/- 2.7 before vs. 100.2 +/- 4.7 g/3 h after training) and of lipids. However, detailed analysis revealed a significant 17% increase in exogenous glucose oxidation, thus indicating a significant sparing of endogenous carbohydrates. In conclusion, physical training induces a modest but significant increase in the oxidation of an oral load of glucose given during subsequent exercise of moderate intensity, a phenomenon reinforcing the sparing of endogenous carbohydrate stores.

Remarkable metabolic availability of oral glucose during long-duration exercise in humans

1986 ◽  
Vol 60 (3) ◽  
pp. 1035-1042 ◽  
Author(s):  
N. Pallikarakis ◽  
B. Jandrain ◽  
F. Pirnay ◽  
F. Mosora ◽  
M. Lacroix ◽  
...  
Keyword(s):  
Lipid Oxidation ◽  
Glucose Oxidation ◽  
Carbohydrate Oxidation ◽  
Oral Glucose ◽  
Total Carbohydrate ◽  
Carbohydrate Utilization ◽  
Exogenous Glucose ◽  
Long Duration ◽  
Glucose Ingestion ◽  
Exercise In Humans

It was reported previously that glucose ingestion prior to or at the beginning of muscular exercise was a readily available metabolic substrate. The aim of this study was to see what percentage of carbohydrate utilization can be covered by glucose ingested regularly during exercise. Male healthy volunteers exercised for 285 min at approximately 45% of their individual maximal O2 uptake on a 10% uphill treadmill. After 15 min adaptation to exercise they received either 200 g (group G 200) or 400 g (group G 400) glucose (0.25 g X ml H2O-1) orally in eight equal doses repeated every 30 min (G 200 = 8 X 25 g, n = 4; G 400 = 8 X 50 g, n = 4). Indirect calorimetry was used to evaluate carbohydrate and lipid oxidation. Naturally labeled [13C]glucose was used to follow the oxidation of the exogenous glucose. Total carbohydrate oxidation was 341 +/- 22 and 332 +/- 32 g, lipid oxidation was 119 +/- 8 and 105 +/- 5 g, and exogenous glucose oxidation was 137 +/- 4 and 227 +/- 13 g (P less than 0.005) in groups G 200 and G 400, respectively. Endogenous glucose oxidation was about half in G 400 of what it was in G 200: 106 +/- 27 vs. 204 +/- 24 g (P less than 0.02). During the last hour of exercise, exogenous oxidation represented 55.3 and 87.5% of total carbohydrate oxidation for groups G 200 and G 400, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic availability of glucose ingested 3 h before prolonged exercise in humans

1984 ◽  
Vol 56 (5) ◽  
pp. 1314-1319 ◽  
Author(s):  
B. Jandrain ◽  
G. Krzentowski ◽  
F. Pirnay ◽  
F. Mosora ◽  
M. Lacroix ◽  
...  
Keyword(s):  
Glucose Oxidation ◽  
Exercise Bout ◽  
Moderate Intensity ◽  
Total Carbohydrate ◽  
Exogenous Glucose ◽  
Plasma Insulin Levels ◽  
Exercise Induced ◽  
Total Glucose ◽  
Blood Glucose Concentrations ◽  
Exercise In Humans

The aim of the present study was to investigate the extent to which an oral load of glucose ingested 3 h before a 4-h exercise bout of moderate intensity represents an energy source readily available during that exercise. Therefore, five healthy male volunteers drank 100 g of naturally labeled [13C]glucose dissolved in 400 ml of water, rested for 3 h, and then exercised on a treadmill for the next 4 h at about 45% of their individual maximum O2 consumption. Total glucose oxidation was derived from nonprotein respiratory quotient and exogenous glucose oxidation evaluated by the 13C methodology as previously described. Total carbohydrate oxidation averaged 285 +/- 17 g during the 7 h of the test, the global amount of carbohydrate oxidized during the exercising period was 253.1 +/- 16.9 g/4 h. Exogenous glucose oxidation averaged 11.3 +/- 0.7 g during the 3-h period of rest and increased markedly after the beginning of exercise, reaching 18.9 +/- 2.2 g/30 min during the first 30 min of exercise; the total amount of exogenous glucose oxidized during the 4 h of exercise was 67.5 +/- 9.4 g. Throughout the whole period of exercise, blood glucose concentrations remained between 3.5 and 4.0 mmol/l. Exercise induced a major fall in plasma insulin levels that reached undetectable values after 3 and 4 h, whereas plasma glucagon levels tended to rise, but their level never significantly exceeded the basal values; plasma free fatty acids and glycerol increased markedly during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Exogenous glucose oxidation during exercise in endurance-trained and untrained subjects

1997 ◽  
Vol 82 (3) ◽  
pp. 835-840 ◽  
Author(s):  
A. E. Jeukendrup ◽  
M. Mensink ◽  
W. H. M. Saris ◽  
A. J. M. Wagenmakers
Keyword(s):  
Energy Expenditure ◽  
Glucose Oxidation ◽  
Glucose Solution ◽  
Fuel Mixture ◽  
Fat Oxidation ◽  
Oxidation Rates ◽  
Exogenous Glucose ◽  
Glucose Ingestion ◽  
Relative Exercise Intensity ◽  
Endogenous Carbohydrates

Jeukendrup, A. E., M. Mensink, W. H. M. Saris, and A. J. M. Wagenmakers. Exogenous glucose oxidation during exercise in endurance-trained and untrained subjects. J. Appl. Physiol. 82(3): 835–840, 1997.—To investigate the effect of training status on the fuel mixture used during exercise with glucose ingestion, seven endurance-trained cyclists (Tr; maximum O2 uptake 67 ± 2.3 ml ⋅ kg−1 ⋅ min−1) and eight untrained subjects (UTr; 48 ± 2 ml ⋅ kg−1 ⋅ min−1) were studied during 120 min of exercise at ∼60% maximum O2 uptake. At the onset of exercise, 8 ml ⋅ kg−1 ⋅ min−1of an 8% naturally enriched [13C]glucose solution was ingested and 2 ml/kg every 15 min thereafter. Energy expenditure was higher in Tr subjects compared with UTr subjects (3,404 vs. 2,630 kJ; P < 0.01). During the second hour, fat oxidation was higher in Tr subjects (37 ± 2 g) compared with UTr subjects (23 ± 1 g), whereas carbohydrate oxidation was similar (116 ± 8 g in Tr subjects vs. 114 ± 4 g in UTr subjects). No differences were observed in exogenous glucose oxidation (50 ± 2 g in Tr subjects and 45 ± 3 g in UTr subjects, respectively). Peak exogenous glucose oxidation rates were similar in the two groups (0.95 ± 0.07 g/min in Tr subjects and 0.96 ± 0.03 g/min in UTr subjects). It is concluded that the higher energy expenditure in Tr subjects during exercise at the same relative exercise intensity is entirely met by a higher rate of fat oxidation without changes in the rates of exogenous and endogenous carbohydrates.

Availability of glucose given orally during exercise

1984 ◽  
Vol 56 (2) ◽  
pp. 315-320 ◽  
Author(s):  
G. Krzentowski ◽  
B. Jandrain ◽  
F. Pirnay ◽  
F. Mosora ◽  
M. Lacroix ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Glucose Disposal ◽  
Moderate Intensity ◽  
Oral Glucose ◽  
Total Carbohydrate ◽  
Glucose Response ◽  
Exogenous Glucose ◽  
Glucose Ingestion ◽  
Group A ◽  
Group B

Adequate utilization of glucose given orally during prolonged muscular exercise remains a matter of controversy. The aim of the present study was to investigate whether the time when glucose is ingested during exercise affects exogenous glucose disposal. Nine healthy male volunteers were submitted to a 4-h period of treadmill exercise at about 45% of their maximum O2 consumption. A 100-g load of naturally labeled [13C]glucose was given orally after 120 min (5 subj, group A) or 15 min (4 subj, group B) of exercise. In the 2 h after glucose ingestion, total carbohydrate oxidation (indirect calorimetry) was similar in both groups (A: 147 +/- 12 g/2 h; B: 135 +/- 12 g/2 h) as was lipid oxidation (A: 51 +/- 4 g/2 h; B: 57 +/- 11 g/2 h). Exogenous glucose oxidation was 54 +/- 2 g/h in group A vs. 55 +/- 6 g/2 h in group B. The blood glucose response to oral glucose was similar in the two conditions, whereas the C-peptide response, already modest, was further blunted when glucose was ingested after 2 h of exercise compared with the response observed after 15 min. In conclusion, glucose ingestion during prolonged exercise of moderate intensity is effectively oxidized, 55% of the load given being recovered as expired CO2 within 2 h; utilization of glucose given orally is similar when ingestion takes place 15 or 120 min after initiation of exercise.

scholarly journals Reduced oxidation rates of ingested glucose during prolonged exercise with low endogenous CHO availability

1996 ◽  
Vol 81 (5) ◽  
pp. 1952-1957 ◽  
Author(s):  
Asker E. Jeukendrup ◽  
Lars B. Borghouts ◽  
Wim H. M. Saris ◽  
Anton J. M. Wagenmakers
Keyword(s):  
Prolonged Exercise ◽  
Glucose Solution ◽  
Exercise Bout ◽  
Random Order ◽  
Plasma Free Fatty Acid ◽  
Moderate Intensity ◽  
Moderate Intensity Exercise ◽  
Oxidation Rates ◽  
The Third ◽  
Exogenous Glucose

Jeukendrup, Asker E., Lars B. Borghouts, Wim H. M. Saris, and Anton J. M. Wagenmakers. Reduced oxidation rates of ingested glucose during prolonged exercise with low endogenous CHO availability. J. Appl. Physiol. 81(5): 1952–1957, 1996.—This study investigated the effect of endogenous carbohydrate (CHO) availability on oxidation rates of ingested glucose during moderate-intensity exercise. Seven well-trained cyclists performed two trials of 120 min of cycling exercise in random order at 57% maximal O2 consumption. Preexercise glycogen concentrations were manipulated by glycogen-lowering exercise in combination with CHO restriction [low-glycogen (LG) trial] or CHO loading [moderate-to-high-glycogen (HG) trial]. In the LG and HG trials, subjects ingested 4 ml/kg body wt of an 8% corn-derived glucose solution of high natural13C abundance at the start, followed by boluses of 2 ml/kg every 15 min. The third trial, in which potato-derived glucose was ingested, served as a control test for background correction. Exogenous glucose oxidation rates were calculated from the 13C enrichment of the ingested glucose and of the breath CO2. Total CHO oxidation was lower in the LG trial than in the HG trial during 60–120 min of exercise [84 ± 7 (SE) vs. 116 ± 8 g; P < 0.05]. Exogenous CHO oxidation in this period was 28% lower in the LG trial compared with the HG trial. Maximal exogenous oxidation rates were also lower ( P < 0.05) in the LG trial (0.64 ± 0.05 g/min) than in the HG trial (0.88 ± 0.04 g/min). This decreased utilization of exogenous glucose was accompanied by increased plasma free fatty acid levels (2–3 times higher) and lower insulin concentrations. It is concluded that glycogen-lowering exercise, performed the evening before an exercise bout, in combination with CHO restriction leads to a reduction of the oxidation rate of ingested glucose during moderate-intensity exercise.

Effect of osmolality on availability of glucose ingested during prolonged exercise in humans

1989 ◽  
Vol 67 (1) ◽  
pp. 76-82 ◽  
Author(s):  
B. J. Jandrain ◽  
F. Pirnay ◽  
M. Lacroix ◽  
F. Mosora ◽  
A. J. Scheen ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Metabolic Response ◽  
Glucose Solution ◽  
Exercise Bout ◽  
Glucose Disposal ◽  
Total Carbohydrate ◽  
Experimental Conditions ◽  
Glucose Response ◽  
Oxidation Rates ◽  
Exogenous Glucose

The aim of this study was to investigate whether the osmolality of a glucose solution, ingested at the beginning of a prolonged exercise bout, affects exogenous glucose disposal. We investigated the hormonal and metabolic response to a 50-g glucose load dissolved in either 200 (protocol A), 400 (protocol B), or 600 (protocol C) ml of water and given orally 15 min after adaptation to exercise in five healthy male volunteers. Naturally labeled [13C]glucose was used to follow the conversion of the ingested glucose to expired-air CO2. Total carbohydrate oxidation (indirect calorimetry) was similar in the three protocols (A, 237 +/- 20; B, 258 +/- 17; C, 276 +/- 20 g/4 h), as was lipid oxidation (A, 128 +/- 4; B, 132 +/- 15; C, 124 +/- 12 g/4 h). Exogenous glucose oxidation rates were similar under the three experimental conditions, and the total amount of exogenous glucose utilized was slightly, but not significantly, increased with the more diluted solution (A, 42.6 +/- 4.4; B, 43.4 +/- 4.1; C, 48.7 +/- 7.2 g/4 h). The blood glucose response was similar in the three protocols. Thus, within the range investigated, the osmolality of the glucose solution ingested had no significant influence either on its oxidation (which was 86–98% of the load ingested) or on the utilization of endogenous carbohydrate, lipid, or protein stores.

Fate of exogenous glucose during exercise of different intensities in humans

1982 ◽  
Vol 53 (6) ◽  
pp. 1620-1624 ◽  
Author(s):  
F. Pirnay ◽  
J. M. Crielaard ◽  
N. Pallikarakis ◽  
M. Lacroix ◽  
F. Mosora ◽  
...  
Keyword(s):  
Lipid Oxidation ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Treadmill Exercise ◽  
Work Load ◽  
Intense Exercise ◽  
Vo2 Max ◽  
Total Carbohydrate ◽  
Exogenous Glucose ◽  
Adaptation To Exercise

The extent to which an oral load of glucose is absorbed from the gut and oxidized during prolonged exercise is a matter of controversy. Four healthy volunteers, 18–28 yr, were submitted on 4 different days to a 105-min treadmill exercise at 22, 39, 51, and 64% of their individual VO2max. After 15 min adaptation to exercise, they received orally 100 g naturally labeled [13C]glucose. Oxidation of the exogenous glucose was followed by 13CO2 measurements in the expired air; total carbohydrate and lipid oxidation were evaluated by indirect calorimetry. Between 22 and 51% VO2 max, total carbohydrate, lipid oxidation, and exogenous glucose oxidation were linearly correlated with the relative work load (r = 0.81; P less than 0.01). Between 51 and 64% VO2 max, exogenous glucose oxidation and lipid oxidation tended to level off, whereas endogenous carbohydrate oxidation was markedly enhanced. The lesser contribution of exogenous glucose during the most intense exercise might be due to a decrease in the oxidation in the muscles or to a lesser availability of this exogenous glucose.

IMCL area density, but not IMCL utilization, is higher in women during moderate-intensity endurance exercise, compared with men

2007 ◽  
Vol 293 (6) ◽  
pp. R2336-R2342 ◽  
Author(s):  
Michaela C. Devries ◽  
Stuart A. Lowther ◽  
Alexander W. Glover ◽  
Mazen J. Hamadeh ◽  
Mark A. Tarnopolsky
Keyword(s):  
Lipid Oxidation ◽  
Endurance Exercise ◽  
Oxidation Rate ◽  
Respiratory Exchange Ratio ◽  
Exercise Bout ◽  
Moderate Intensity ◽  
Intramyocellular Lipid ◽  
Area Density ◽  
Net Use ◽  
Before And After

Women use more fat during endurance exercise as evidenced by a lower respiratory exchange ratio (RER). The contribution of intramyocellular lipid (IMCL) to lipid oxidation during endurance exercise is controversial, and studies investigating sex differences in IMCL utilization have found conflicting results. We determined the effect of sex on net IMCL use during an endurance exercise bout using an ultrastructural evaluation. Men ( n = 17) and women ( n = 19) completed 90-min cycling at 63% V̇o2peak. Biopsies were taken before and after exercise and fixed for electron microscopy to determine IMCL size, # IMCL/area, IMCL area density, and the % IMCL touching mitochondria. Women had a lower RER and carbohydrate oxidation rate and a higher lipid oxidation rate during exercise ( P < 0.05), compared with men. Women had a higher # IMCL/area and IMCL area density ( P < 0.05), compared with men. Women, but not men, had a higher % IMCL touching mitochondria postexercise ( P = 0.03). Exercise decreased IMCL area density ( P = 0.01), due to a decrease in the # IMCL/area ( P = 0.02). There was no sex difference in IMCL size or net use. In conclusion, women have higher IMCL area density compared with men, due to an increased # IMCL and not an increased IMCL size, as well as an increased % IMCL touching mitochondria postexercise. Endurance exercise resulted in a net decrease in IMCL density due to decreased number of IMCL, not decreased IMCL size, in both sexes.

Changes in breath 13CO2/12CO2 during exercise of different intensities

1996 ◽  
Vol 81 (3) ◽  
pp. 1096-1102 ◽  
Author(s):  
J. F. Gautier ◽  
F. Pirnay ◽  
M. Lacroix ◽  
F. Mosora ◽  
A. J. Scheen ◽  
...  
Keyword(s):  
Respiratory Exchange Ratio ◽  
Exercise Bout ◽  
Glucose Load ◽  
O2 Uptake ◽  
Individual Values ◽  
Exogenous Glucose ◽  
Endogenous Substrates ◽  
Intensity Of Exercise ◽  
Endogenous Carbohydrates ◽  
Expired Air

The measurement of breath 13CO2/12CO2 is commonly used during exercise to evaluate the oxidation rate of exogenous carbohydrates enriched in 13C. The aim of this study was to investigate whether exercise itself affects the 13C/12C ratio in expired air CO2 in relation to exercise intensity. The relative abundance of 13C and 12C in expired air CO2 was determined by isotoperatio mass spectrometry and expressed as delta 13C (in %o) by using Craig's formula and calibrated standards. Five healthy young men exercised on a treadmill after an overnight fast during > or = 105 min on four occasions and in a randomized order. Work rates were performed at approximately 30, 45, 60, and 75% of their maximal O2 uptake (VO2max). Delta 13C in expired air CO2 and respiratory exchange ratio (RER) were determined every 15 or 30 min during exercise. At 30 and 45% VO2max, a slight and not statistically significant increase in delta 13C was observed at 30 min. In contrast, at 60 75% VO2max, the rise was statistically significant and averaged 0.83 and 0.99%o, respectively. Average delta 13C (between 0 and 105 min) progressively increased with the intensity of exercise. Individual values of delta 13C and RER were positively correlated (r = 0.653, P = 0.002) as were values of delta 13C and endogenous carbohydrates utilized (r = 0.752, P < 0.001). Factitious or "pseudooxidation" of a 13C-enriched exogenous glucose load (indeed noningested) was calculated from the changes in expired air delta 13C. Over the whole period of exercise it was not statistically significant at 30 and 40% VO2max. However, over the first 60 min of exercise, such pseudooxidation of exogenous glucose was significant at 30 and 45% VO2max. In conclusion, by modifying the mix of endogenous substrates oxidized, exercise at 60% VO2max and above significantly increases the 13C/12C ratio in expired air CO2. At these intensities, this could lead to overestimation of the oxidation of 13C-labeled substrates given orally. At lower intensities of exercise, such overestimation is much smaller an affects mainly the values recorded during the initial part of the exercise bout.

scholarly journals Acute Hypoxia Suppresses Exogenous Glucose Oxidation, Lowers Fat Oxidation, and Increases Muscle Glycogenolysis During Steady-state Aerobic Exercise (P08-084-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Lee Margolis ◽  
Marques Wilson ◽  
Claire Whitney ◽  
Christopher Carrigan ◽  
Nancy Murphy ◽  
...  
Keyword(s):  
Steady State ◽  
Aerobic Exercise ◽  
Glucose Oxidation ◽  
Acute Hypoxia ◽  
Fat Oxidation ◽  
Carbohydrate Oxidation ◽  
Hepatic Glycogen ◽  
Total Carbohydrate ◽  
Carbohydrate Ingestion ◽  
Exogenous Glucose

Abstract Objectives Lowlanders performing steady-state aerobic exercise during high-altitude (HA) sojourns, hypoxia mediates increased endogenous carbohydrate oxidation compared to sea level (SL). At SL, ingesting carbohydrate during exercise spares endogenous carbohydrate stores and improves endurance. However, it is unclear whether that strategy is effective at HA, as data from a recent study suggests exogenous glucose oxidation is suppressed during aerobic exercise performed 5 hr after arriving at HA. This observation has not been replicated. The objective of this study was to determine substrate oxidative responses to exogenous carbohydrate ingestion during steady-state aerobic exercise at SL and HA. Methods Using a randomized, crossover design, native lowlanders (n = 8 males, mean ± SD, age: 23 ± 2 yr, body mass: 87 ± 10 kg, and VO2peak: SL 4.3 ± 0.2 L/min and HA 2.9 ± 0.2 L/min) consumed 145 g (1.8 g/min) of glucose while performing 80 min of metabolically-matched (SL: 1.66 ± 0.14 L/min 347 ± 29 kcal, HA: 1.59 ± 0.10 L/min, 369 ± 39 kcal) treadmill exercise at SL (757 mmHg) and HA (460 mmHg) conditions after a 5 hr exposure. Total carbohydrate and fat oxidation rates (g/min) during exercise were determined by indirect calorimetry, and exogenous, muscle- and hepatic-derived glucose oxidation by tracer technique using breath and blood measurements of 13C-glucose. Results Total carbohydrate oxidation was higher (P < 0.05) at HA (2.15 ± 0.32) compared to SL (1.39 ± 0.14). Exogenous glucose oxidation was lower (P < 0.05) at HA (0.35 ± 0.07) than SL (0.44 ± 0.05). Muscle glycogen oxidation was higher at HA (1.67 ± 0.26) compared to SL (0.83 ± 0.13). There was no difference in hepatic glycogen oxidation between SL (0.13 ± 0.03) and HA (0.13 ± 0.04). Fat oxidation was lower at HA (0.05 ± 0.07) than SL (0.31 ± 0.08). Conclusions These data confirm that acute hypoxic exposure suppresses exogenous carbohydrate oxidation during steady-state exercise. Coupled with observations that fat oxidation was reduced and muscle glycogenolysis accelerated in hypoxia, these findings suggest that ingesting carbohydrate during exercise upon acute hypoxia exposure is not an effective strategy for attenuating oxidation of endogenous carbohydrate stores. Funding Sources Views expressed are the authors and do not reflect the official policy of the Army, DoD, or the U.S. Government. Supported by USAMRMC.

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