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Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance.
Eur J Appl Physiol. 2003 Jan; 88(4-5):444-52.EJ

Abstract

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.

Authors+Show Affiliations

Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, B15 2TT, Birmingham, UK.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

12527976

Citation

Jentjens, R L P G., et al. "Effects of Pre-exercise Ingestion of Differing Amounts of Carbohydrate On Subsequent Metabolism and Cycling Performance." European Journal of Applied Physiology, vol. 88, no. 4-5, 2003, pp. 444-52.
Jentjens RL, Cale C, Gutch C, et al. Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance. Eur J Appl Physiol. 2003;88(4-5):444-52.
Jentjens, R. L., Cale, C., Gutch, C., & Jeukendrup, A. E. (2003). Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance. European Journal of Applied Physiology, 88(4-5), 444-52.
Jentjens RL, et al. Effects of Pre-exercise Ingestion of Differing Amounts of Carbohydrate On Subsequent Metabolism and Cycling Performance. Eur J Appl Physiol. 2003;88(4-5):444-52. PubMed PMID: 12527976.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of pre-exercise ingestion of differing amounts of carbohydrate on subsequent metabolism and cycling performance. AU - Jentjens,R L P G, AU - Cale,C, AU - Gutch,C, AU - Jeukendrup,A E, Y1 - 2002/11/27/ PY - 2002/04/15/accepted PY - 2003/1/16/pubmed PY - 2003/7/23/medline PY - 2003/1/16/entrez SP - 444 EP - 52 JF - European journal of applied physiology JO - Eur. J. Appl. Physiol. VL - 88 IS - 4-5 N2 - 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. SN - 1439-6319 UR - https://www.unboundmedicine.com/medline/citation/12527976/Effects_of_pre_exercise_ingestion_of_differing_amounts_of_carbohydrate_on_subsequent_metabolism_and_cycling_performance_ L2 - https://dx.doi.org/10.1007/s00421-002-0727-9 DB - PRIME DP - Unbound Medicine ER -