Augmented muscle glycogen utilization following a single session of sprint training in hypoxia

Elevated plasma fatty acids have been shown to spare muscle glycogen during exercise. However, on the basis of recent findings, the saturation of fatty acids may influence this response. The purpose of this study was to determine whether saturated or unsaturated fatty acids affected muscle glycogenolysis to varying degrees during cycle exercise. Five healthy men completed three 60-min cycle ergometer trials (EX) at approximately 70% maximal O2 uptake (VO2max). Triglyceride levels were elevated by a fat feeding (FF) composed of 90% saturated fatty acids (heavy whipping cream, 90 g) or by the infusion of Intralipid (IL; Clintec Nutrition; 45 ml/h of 20% IL, 9.0 g), which was 85% unsaturated. A control trial (CON) consisted of a light breakfast (43 g carbohydrate and 1 g fat). Heparin (2,000 U) was administered 15 min before EX in FF and IL trials, resulting in one- and threefold increases in free fatty acid (FFA) levels in IL and FF, respectively. Pre-EX muscle glycogen did not differ. The utilization of muscle glycogen during 60 min of EX was less (P < 0.05) during the FF (60.0 +/- 5.2 mmol/kg wet wt) and IL (58.6 +/- 6.2 mmol/kg wet wt) compared with CON (81.8 +/- 7.5 mmol/kg wet wt). There was no difference between FF and IL in the amount of glycogen utilized. Serum triglyceride levels were greater (P < 0.05) at preheparin in FF (1.58 +/- 0.37 mmol/l) and IL (0.98 +/- 0.13 mmol/l) compared with CON (0.47 +/- 0.14 mmol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

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Substrate utilization in leg muscle of men after heat acclimation

Journal of Applied Physiology ◽

10.1152/jappl.1987.63.1.31 ◽

1987 ◽

Vol 63 (1) ◽

pp. 31-35 ◽

Cited By ~ 27

Author(s):

J. P. Kirwan ◽

D. L. Costill ◽

H. Kuipers ◽

M. J. Burrell ◽

W. J. Fink ◽

...

Keyword(s):

Blood Flow ◽

Muscle Glycogen ◽

Respiratory Exchange Ratio ◽

Plasma Free Fatty Acid ◽

Heat Acclimation ◽

Substrate Utilization ◽

Acclimation Period ◽

Glycogen Utilization ◽

Leg Muscle ◽

Increased Blood Flow

Eight men were heat acclimated (39.6 degrees C and 29.2% rh) for 8 days to examine changes in substrate utilization. A heat exercise test (HET), (cycling for 60 min; 50% maximal O2 consumption) was performed before (UN-HET) and after (ACC-HET) the acclimation period. Muscle glycogen utilization (67.0 vs. 37.6 mmol/kg wet wt), respiratory exchange ratio (0.85 +/- 0.002 vs. 0.83 +/- 0.001), and calculated rate of carbohydrate oxidation (75.15 +/- 1.38 vs. 64.80 +/- 1.52 g/h) were significantly reduced (P less than 0.05) during the ACC-HET. Significantly lower (P less than 0.05) femoral venous glucose (15, 30, and 45 min) and lactate (15 min) levels were observed during the ACC-HET. No differences were observed in plasma free fatty acid (FFA) and glycerol concentrations or glucose, lactate and glycerol arteriovenous uptake/release between tests. A small but significant increase (P less than 0.05) above resting levels in FFA uptake was observed during the ACC-HET. Leg blood flow was slightly greater (P greater than 0.05) during the ACC-HET (4.64 +/- 0.13 vs. 4.80 +/- 0.13 l/min). These findings indicate a reduced use of muscle glycogen following heat acclimation. However, the decrease is not completely explained by a shift toward greater lipid oxidation or increased blood flow.

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Effect of carbohydrate ingestion on exercise metabolism

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.4.1553 ◽

1988 ◽

Vol 65 (4) ◽

pp. 1553-1555 ◽

Cited By ~ 49

Author(s):

M. Hargreaves ◽

C. A. Briggs

Keyword(s):

Muscle Glycogen ◽

Venous Blood ◽

Cycle Ergometer ◽

Strenuous Exercise ◽

Carbohydrate Ingestion ◽

Ergometer Exercise ◽

Glucose Polymer ◽

Before And After ◽

Plasma Insulin Levels ◽

Glycogen Utilization

Five male cyclists were studied during 2 h of cycle ergometer exercise (70% VO2 max) on two occasions to examine the effect of carbohydrate ingestion on muscle glycogen utilization. In the experimental trial (CHO) subjects ingested 250 ml of a glucose polymer solution containing 30 g of carbohydrate at 0, 30, 60, and 90 min of exercise; in the control trial (CON) they received an equal volume of a sweet placebo. No differences between trials were seen in O2 uptake or heart rate during exercise. Venous blood glucose was similar before exercise in both trials, but, on average, was higher during exercise in CHO [5.2 +/- 0.2 (SE) mmol/l] compared with CON (4.8 +/- 0.1, P less than 0.05). Plasma insulin levels were similar in both trials. Muscle glycogen levels were also similar in CHO and CON both before and after exercise; accordingly, there was no difference between trials in the amount of glycogen used during the 2 h of exercise (CHO = 62.8 +/- 10.1 mmol/kg wet wt, CON = 56.9 +/- 10.1). The results of this study indicate that carbohydrate ingestion does not influence the utilization of muscle glycogen during prolonged strenuous exercise.

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EFFECTS OF GLUCOSE POLYMER INGESTION ON MUSCLE GLYCOGEN UTILIZATION DURING A SOCCER MATCH

Medicine & Science in Sports & Exercise ◽

10.1249/00005768-198604001-00027 ◽

1986 ◽

Vol 18 (supplement) ◽

pp. S6 ◽

Cited By ~ 2

Author(s):

P. B. Leatt ◽

I. Jacobs

Keyword(s):

Muscle Glycogen ◽

Soccer Match ◽

Glucose Polymer ◽

Glycogen Utilization

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Epinephrine inhibits exogenous glucose utilization in exercising horses

Journal of Applied Physiology ◽

10.1152/jappl.2000.88.5.1777 ◽

2000 ◽

Vol 88 (5) ◽

pp. 1777-1790 ◽

Cited By ~ 30

Author(s):

Raymond J. Geor ◽

Kenneth W. Hinchcliff ◽

Laura Jill McCutcheon ◽

Richard A. Sams

Keyword(s):

Muscle Glycogen ◽

Glucose Utilization ◽

Treadmill Exercise ◽

Moderate Intensity ◽

Oral Glucose ◽

Moderate Intensity Exercise ◽

Epinephrine Infusion ◽

Glucose Administration ◽

Exogenous Glucose ◽

Glycogen Utilization

This study examined the effects of preexercise glucose administration, with and without epinephrine infusion, on carbohydrate metabolism in horses during exercise. Six horses completed 60 min of treadmill exercise at 55 ± 1% maximum O2 uptake 1) 1 h after oral administration of glucose (2 g/kg; G trial); 2) 1 h after oral glucose and with an intravenous infusion of epinephrine (0.2 μmol ⋅ kg− 1 ⋅ min− 1; GE trial) during exercise, and 3) 1 h after water only (F trial). Glucose administration (G and GE) caused hyperinsulinemia and hyperglycemia (∼8 mM). In GE, plasma epinephrine concentrations were three- to fourfold higher than in the other trials. Compared with F, the glucose rate of appearance was ∼50% and ∼33% higher in G and GE, respectively, during exercise. The glucose rate of disappearance was ∼100% higher in G than in F, but epinephrine infusion completely inhibited the increase in glucose uptake associated with glucose administration. Muscle glycogen utilization was higher in GE [349 ± 44 mmol/kg dry muscle (dm)] than in F (218 ± 28 mmol/kg dm) and G (201 ± 35 mmol/kg dm). We conclude that 1) preexercise glucose augments utilization of plasma glucose in horses during moderate-intensity exercise but does not alter muscle glycogen usage and 2) increased circulating epinephrine inhibits the increase in glucose rate of disappearance associated with preexercise glucose administration and increases reliance on muscle glycogen for energy transduction.

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