Blood glucose responses to carbohydrate feeding prior to exercise in the heat: Effects of hypohydration and rehydration

M. Echegaray, L. E. Armstrong, C. M. Maresh, D. Riebe, R. W. Kenefick, J. W. Castellani, S. Kavouras, D. Casa

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

This study assessed the plasma glucose (PG) and hormonal responses to carbohydrate ingestion, prior to exercise in the heat, in a hypohydrated state versus partial rehydration with intravenous solutions. On separate days, 8 subjects (21.0 ± 1.8 years; 57.3 ± 3.7 ml · kg-1 min-1) exercised at 50% V̇O2max in a 33 °C environment until a 4% body weight loss was achieved. Following this, subjects were rehydrated (25 ml · kg-1) with either: 0.45% IV saline (45IV), 0.9% IV saline (9IV), or no fluid (NF). Subjects then ingested 1 g · kg-1 of carbohydrate and underwent an exercise test (treadmill walking, 50% V̇O2max, 36 °C) for up to 90 min. Compared to pre-exercise level (294 mg · dl-1), PG increased significantly (>124 mg · dl-1) at 15 min of the exercise test in all trials and remained significantly elevated for 75 min in NF, 30 min more than in the 2 rehydration trials. Although serum Insulin increased significantly at 15 min of exercise in the 45IV trial (7.2 ± 1.2 vs. 23.7 ± 4.7 μIU · ml-1), no significant differences between trials were observed. Peak plasma norepinephrine was significantly higher in NF (640 ± 66 pg · ml-1) compared to the 45IV and 9IV trials (472 ± 55 and 474 ± 52 pg · ml-1, respectively). In conclusion, ingestion of a small solid carbohydrate load prior to exercise in the 4% hypohydration level resulted in prolonged high PG concentration compared to partial IV rehydration.

Original languageEnglish (US)
Pages (from-to)72-83
Number of pages12
JournalInternational journal of sport nutrition
Volume11
Issue number1
DOIs
StatePublished - Jan 1 2001
Externally publishedYes

Keywords

  • Catecholamines
  • Dehydration
  • Insulin
  • Intravenous-saline

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science
  • Endocrinology
  • Public Health, Environmental and Occupational Health

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