The effects of low and high glycemic index 24-h recovery diets on cycling time trial performance

• Published in: Journal of sports medicine and physical fitness Vol. 51; no. 2; pp. 233 - 240
• Main Authors: MOORE, L. J. S, MIDGLEY, A. W, VINCE, R, MCNAUGHTON, L. R
• Format: Journal Article
• Language: English
• Published: Torino Minerva medica 01-06-2011; Edizioni Minerva Medica
• Subjects: Adult; Athletes; Athletic Performance - physiology; Bicycling; Bicycling - physiology; Biological and medical sciences; Carbohydrates; Cross-Over Studies; Diet; Dietary Carbohydrates - administration & dosage; Fundamental and applied biological sciences. Psychology; Glycemic Index; Human performance; Humans; Male; Physical Endurance - physiology; Vertebrates: body movement. Posture. Locomotion. Flight. Swimming. Physical exercise. Rest. Sports; Human; Carbohydrates; Sport; Diet; Carbohydrate; Physiology; Ergometry; Recovery; Feeding
• ISSN: 0022-4707; 1827-1928

The present study investigated the effects of high and low glycemic index (GI) 24 h recovery meals on the physiological responses and subsequent athletic performance, following a glycogen depleting protocol.
Ten well trained cyclists (age, 33.6±7.4y, height, 175.3±7.6 cm, weight 74.5±8.2 kg, and VO(2max), 60.5±6.0 ml∙kg(-1)∙min(-1)) participated in two trials in a randomized cross- over design. On day 1, subjects performed a glycogen depleting protocol after which they then consumed either high or low GI recovery diets over the next 24 h, which provided 8 g.kgBW(-1) of carbohydrate. On day 2, the subjects returned to the laboratory, 2- 3 h postprandial, to perform a 40 km time trial (TT) on the Velotron cyclePro© ergometer.
No difference was observed in TT performance times between the high GI (93. 5±9.29 min) trial and the low GI (90.7±11.1 min) trial (t=1.1; P=0.35). Additionally, no differences in carbohydrate (F=1.1, P=0.37) fat (F=1.1, P=0.40) oxidation or blood glucose concentration (F=0.9, P=0.5) was observed.
The results of the present study suggest that the ingestion of a high GI carbohydrate 24 h recovery diet following glycogen depleting exercise, has no greater effect on endurance performance than consuming a low GI carbohydrate 24 h recovery diet. It may be concluded from these results that, provided enough carbohydrate is consumed during a 24 h recovery period, there is no difference in subsequent endurance performance.