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

Koivisto, Veikko A.; Härkönen, Matti; Karonen, S.-L.; Groop, Per Henrik; Elovainio, R.; Ferrannini, Ele; Saccà, Luigi; DeFronzo, Ralph A.

doi:10.1152/jappl.1985.58.3.731

Cited by 56 publications

(23 citation statements)

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“…The inability of liver glycogen to replace blood glucose at the same rate as muscle takes up this substrate may lead to hypoglycaemia26'27 28. Nevertheless, blood glucose concentration returned to pre-exercise levels after 45min of exercise in the G trial, which is a response which is similar to findings in other studies11 19,22,28 Felig et al29 suggested that during prolonged exercise, hypoglycaemia per se does not cause fatigue and its prevention does not delay exhaustion. In the present study blood glucose concentrations were over 4 mmol 1-1 at exhaustion during both the G and P trials and so fatigue was not the result of hypoglycaemia.…”

Section: Discussionsupporting

confidence: 87%

The influence of pre-exercise glucose ingestion on endurance running capacity.

1994

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There are only two studies which provide substantial evidence for this view7 8. Costill and colleagues reported that the ingestion of a concentrated glucose solution 45 min before the start of submaximal treadmill running caused a greater rate of muscle glycogen utilization than when exercise was performed after drinking water. This increased rate of glycogenolysis would, it was proposed, lead to an early onset of fatigue during prolonged exercise. Foster and colleagues8 confirmed this hypothesis in a study which showed that cycling time to exhaustion was reduced by 19% when their subjects ingested a 25% glucose solution 30 min before exercise. Muscle glycogen concentrations were not measured but the study did show an elevation in serum insulin and a reduction in serum fatty acid concentrations8. The cause of the early onset of fatigue was, according to the authors, a decrease in the availability of serum fatty acids for muscle metabolism which, in turn, increased the rate of muscle glycogen depletion and caused the early onset of fatigue9.Therefore, the explanation offered by Foster and colleagues8 for the paradoxical onset of fatigue following the pre-exercise ingestion of a concentrated glucose solution is, in theory, sound. But closer examination of the results of their study leaves several questions unanswered. For example, the rates of carbohydrate oxidation were the same during the glucose and water trials. If there had been an increased rate of glycogenolysis then this latter result is difficult to explain. Furthermore, there were no differences in perceived rates of exertion recorded during the two trials and yet their cyclists exercised for 10 min less on the glucose trial.More recently, however, Fielding et al.10 showed that the pre-exercise ingestion of fructose and glucose solutions had no greater influence on the rate of muscle glycogen utilization during exercise than the pre-exercise ingestion of water. McMurray et al. 1 provided some evidence to show that the pre-exercise ingestion of either glucose or fructose solutions by female runners, before exercise, has no detrimental influence on running performance. The exercise duration in this latter study was only approximately 60 min, probably because of the high exercise intensity (80% VO2max) which in turn resulted in blood lactate concentrations of about 5mmol)1-1 at Br

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Section: Discussionsupporting

confidence: 87%

The influence of pre-exercise glucose ingestion on endurance running capacity.

1994

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“…In contrast, several other studies have found that ingesting CHO in the hour before exercise did not result in an increase in muscle glycogen breakdown (Hargreaves et al 1987;Koivisto et al 1985;Levine et al 1983). Furthermore, in most cases a drop in the blood glucose concentration induced by ingesting CHO preexercise did not negatively affect performance (Alberici et al 1993;Chryssanthopoulos et al 1994;Scott van Zant and Lemon 1997).…”

Section: Introductionmentioning

confidence: 83%

Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance

et al. 2003

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Studies on the effect of the pre-exercise ingestion of carbohydrate on metabolism and performance have produced conflicting results, perhaps because of differences in the designs of the studies. The purpose of the present study was to examine the effects of ingesting differing amounts of glucose pre-exercise on the glucose and insulin responses during exercise and on time-trial (TT) performance. Nine well-trained male cyclists completed four exercise trials separated by at least 3 days. At 45 min before the start of exercise subjects consumed 500 ml of a beverage containing either 0 g (PLAC), 25 g (LOW), 75 g (MED) or 200 g (HIGH) of glucose. The exercise trials consisted of 20 min of submaximal steady-state exercise (SS) at 65% of maximal power output immediately followed by a [mean (SEM)] 691 (12) kJ TT. Plasma insulin concentrations at the onset of exercise were significantly higher ( P<0.05) in MED and HIGH compared with LOW and PLAC. Plasma glucose concentration fell rapidly ( P<0.05) during SS exercise in all glucose trials, but remained steady in PLAC. No difference in plasma glucose concentration was observed between the glucose trials at any time. Hypoglycaemia (less than 3.5 mmol.l(-1)) was observed in six subjects during SS but only after ingesting glucose pre-exercise. However, there was no difference in TT performance between the four trials. The ingestion of 0, 25, 75 or 200 g of glucose 45 min before a 20 min submaximal exercise bout did not affect subsequent TT performance. In addition, mild rebound hypoglycaemia following pre-exercise glucose ingestion did not negatively affect performance.

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“…Recent studies reported that the high glycemic index diet caused rapid elevation of plasma glucose and inhibited lipid oxidation during exercise in trained cyclists (16), and women (17)(18)(19). Pre-exercise insulin elevation by glucose ingestion could cause hypoglycemia during exercise because of enhanced glucose incorporation by insulin and muscle contraction (20) and could cause glycogen depletion (21). In the present study, ESG administration did not elevate plasma insulin level except for the doses of 1.68 mg/g body weight/h (Experiment 3).…”

Section: Discussionmentioning

confidence: 99%

Rapid Rehydration and Moderate Plasma Glucose Elevation by Fluid Containing Enzymatically Synthesized Glycogen

Inagaki

Ishihara

Ishida

et al. 2011

J Nutr Sci Vitaminol

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Summary Enzymatically synthesized glycogen (ESG) has high solubility and its solution has low osmotic pressure. Therefore ESG solution could be rapidly absorbed and could be adequate for water rehydration and carbohydrate supplementation during exercise. The object of this study was to evaluate the gastric emptying time and plasma glucose elevation after an administration of ESG solution in comparison with another carbohydrate solution by using a laboratory animal. Male BALB/c mice were administered 10% w/v solution of glucose, maltodextrin, starch, naturally synthesized glycogen (NSG) and ESG at a dose of 20 L/g body weight for the measurement of gastric emptying rate (Experiment 1) and 10 L/g body weight for the measurement of plasma glucose elevation (Experiment 2). The osmolarity of gastric content was lower in the ESG and maltodextrin group than the other carbohydrate group. Weight of gastric fluid was significantly lower in the ESG and water group than the glucose group ( p Ͻ 0.01). Plasma glucose level was significantly lower in the ESG group than the glucose group from 0 to 60 min after administration ( p Ͻ 0.01), whereas plasma glucose level was same from 60 to 120 min for the ESG and glucose group ( p ϭ 0.948). In Experiment 3, BALB/c mice ran on a treadmill for 2 h and were administered 8% of ESG or glucose solution (1.75, 3.5 or 7.0 L/g body weight) every 20 min during running. There was no difference in post-exercise muscle glycogen level. These data suggest that 1) ESG beverage does not disturb water absorption because of its short gastric emptying time and 2) ESG slowly elevates plasma glucose level and maintains it for a prolonged time compared to the glucose solution.

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

Cited by 56 publications

References 0 publications

The influence of pre-exercise glucose ingestion on endurance running capacity.

The influence of pre-exercise glucose ingestion on endurance running capacity.

Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance

Rapid Rehydration and Moderate Plasma Glucose Elevation by Fluid Containing Enzymatically Synthesized Glycogen

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