Metabolism and performance during extended high-intensity intermittent exercise after consumption of low- and high-glycaemic index pre-exercise meals.
The metabolic and performance benefits of prior consumption of low-glycaemic index (GI) meals v. high-GI meals were determined in extended high-intensity intermittent exercise. Participants (ten males and four females, aged 25·8 (sd 7·3) years) completed two testing days (each consisting of back-to-back 90-min intermittent high-intensity treadmill running protocols separated by 3 h) spaced by at least 7 d. Using a randomised counterbalanced cross-over design, low-GI, lentil-based meals (GI about 42) or high-GI, potato-based meals (GI about 78) matched for energy value were consumed 2 h before, and within 1 h after, the first exercise session. Performance was measured by the distance covered during five 1-min sprints (separated by 2·5 min walking) at the end of each exercise session. Peak postprandial blood glucose was higher by 30·8 % in the high-GI trial compared with the low-GI trial, as was insulin (P = 0·039 and P = 0·003, respectively). Carbohydrate oxidation was lower by 5·5 % during the low-GI trials compared with the high-GI trials at the start of the first exercise session (P < 0·05). Blood lactate was significantly higher (6·1 v. 2·6 mmol/l; P = 0·019) and blood glucose significantly lower (4·8 v. 5·4 mmol/l; P = 0·039) at the end of the second exercise session during the high-GI trial compared with the low-GI trial. Sprint distance was not significantly different between conditions. A low-GI meal improved the metabolic profile before and during extended high-intensity intermittent exercise, but did not affect performance. Improvements in metabolic responses when consuming low-GI meals before exercise may be beneficial to the long-term health of athletes.
College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada.
Christine B
CB
Bennett
Philip D
PD
Chilibeck
Trevor
T
Barss
Hassanali
H
Vatanparast
Albert
A
Vandenberg
Gordon A
GA
Zello
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D018592:Cross-Over Studies; D004040:Dietary Carbohydrates / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D005260:Female; D005502:Food; D038321:Glycemic Index; D006339:Heart Rate; D006801:Humans; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology; D019518:Postprandial Period; D012420:Running / Q000502:physiology
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005227:Fatty Acids; D007328:Insulin; D019344:Lactic Acid