MINERVA MEDICA COPYRIGHT ® Does a pre-exercise carbohydrate feeding improve a 20-km cross-country ski performance? Aim. Carbohydrates are known to improve exercise performance, but their effects on actual competitions are not studied in detail. Aim of the present work was to evaluate the effects of maltodex- trins ingestion on a simulated cross-country ski competition. Methods. Ten athletes (15-24 years) repeated twice, in random order, a 20-km time-trial; 45 min prior to the start, they con- sumed 508±64 mL of a beverage containing either 0.7 g·kg -1 body mass of maltodextrins or carbohydrate free placebo. Results. Blood glucose, lactate and rate of perceived exertion (RPE) were measured periodically; heart rate was acquired con- tinuously. Maltodextrins ingestion did not affect the increase in lactate and RPE at the end of the trial (5.2±3.7 mmol·L -1 and 17.5±2.2), nor heart rate, which was constant throughout the exercises (177.1±4.3 bpm). The environmental conditions changed statistically in the second experimental session (-10.2±1.8°C vs - 0.8±0.5°C for snow temperature, P<0.05), giving rise to shorter performance times of all the athletes (67.9±5.9 min vs 63.5±5.8 min, P<0.005). Within each session, the average performance time of the athletes receiving maltodextrins was shorter, even if not significantly. However, the difference in performance time of the group fed with the maltodextrins the 2nd day, was statistically higher (6.1±1.7 min vs 3.4±1.5 min, P<0.03). The effects of mal- todextrins ingestion were disentangled mathematically, leading to an estimated gain in performance time of 2%. Conclusion. In spite of the different environmental conditions during the 2 experimental sessions, the illustrated results sug- gest an improvement of total performance time following the maltodextrins feeding. KEY WORDS: Time-trial - Maltodextrins - Rate of perceived exer- tion - Performance time. A n adequate carbohydrate (CHO) supply during prolonged muscular work may enhance exercise capacity 1-4 probably by delaying the onset of fatigue. 5 Maximal exercise performance is improved by high glycogen stores, 6 which can be increased by a high CHO diet on the days prior to competition. 7-10 CHO consumption during the effort can enhance both endurance capacity 11-18 and 1 h high intensity exercise performances. 19, 20 A CHO containing meal consumed some hours before the exercise improves time to exhaustion, even after an overnight fast, 17 while a CHO feeding con- sumed 30-45 min prior to the start of exercise does not always delay the onset of fatigue. 21-23 CHO ingest- ed at fatigue do not allow subjects to exercise further. 24 A pre-exercise CHO feeding enhances blood glucose availability in the later stages of exercise and has a pos- itive effect on the central component of fatigue, allow- ing athletes to tolerate the effort for longer periods. 15, 25- 27 However, the pre-exercise CHO feeding can increase plasma insulin concentration, which may induce a decline in plasma glucose during the exercise, thus to a decreased performance. 28, 29 Nevertheless, other studies have shown an increased performance 30, 31 or no effect 32-34 due to the pre-exercise CHO feeding. In spite of the great number of investigations per- formed in the laboratory, little information is avail- Department of Biomedical Sciences and Technologies University of Udine, Udine, Italy Received March 18, 2005. Accepted for publication June 16, 2005. Address reprint requests to: Dr. M. P. Francescato, Department of Biomedical Sciences and Technologies, University of Udine, P.le Kolbe 4, 33100 Udine, Italy. E-mail: MFrancescato@mail.dstb.uniud.it M. P. FRANCESCATO, I. PUNTEL 248 THE JOURNAL OF SPORTS MEDICINE AND PHYSICAL FITNESS June 2006 BODY COMPOSITION, SPORT NUTRITION AND SUPPLEMENTATION (ERGOGENICS) ORIGINAL ARTICLES J SPORTS MED PHYS FITNESS 2006;46:248-56