The effects of glucose polymer beverage ingestion during prolonged outdoor exercise in the heat

Daniel S. Seidman, Itamar Ashkenazi, Ronen Arnon, Yair Shapiro, Yoram Epstein

Research output: Contribution to journalArticlepeer-review

Abstract

The aim of this study was to examine the effect of ingestion of a glucose polymer drink on fluid and metabolic balance during a 30 km outdoor march in the heat (ambient temperature, 26-31°C; relative humidity, 53-34%). The subjects were randomly assigned to one of three groups: 7.2% glucose polymer-electrolyte beverage (GP) (N = 16), flavored sweetened placebo drink (SP) (N = 15), and tap water (TW) (N = 18). The subjects in the three groups consumed similar volumes of fluid, and no differences were found in sweat rate and percent dehydration. Changes in plasma volume were smaller, though not statistically significant, for GP than for SP and TW (−2.8%, −5.4%, −9.4%, respectively). Changes in sodium concentrations and serum osmolality were similar in the three groups. Subjects consuming GP maintained during exercise a significantly higher (P < 0.001) blood glucose concentration (range: 6.5-7.4 mmol•1−1) than the SP and TW groups. They were also found to have increased levels of serum insulin (29.3 ± 18.5 mU•1−1) and no change in serum free fatty acids (0.52 ± 0.19 mmol•1−1). In contrast, subjects ingesting SP or TW had significantly elevated (P < 0.001) concentrations of free fatty acids (range: 1.35-1.74 mmol-1−1) compared with subjects consuming GP (0.35-0.52 mmol•1−1), with no significant change in blood glucose and serum insulin levels over the exercise period. We conclude that highly trained endurance athletes may maintain a higher blood glucose level by consuming GP during prolonged exercise in the heat without impairing fluid replacement.

Original languageEnglish
Pages (from-to)458-462
Number of pages5
JournalMedicine and Science in Sports and Exercise
Volume23
Issue number4
DOIs
StatePublished - Apr 1991

Keywords

  • Blood
  • Dehydration
  • Fluid replacement
  • Glucose
  • Plasma volume
  • Serum free fatty acids
  • Serum insulin

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