Eating, drinking, and cycling. A controlled Tour de France simulation study, Part I.

Sustained exhausting exercise is thought to depress appetite and food intake. The aim of the present investigation was to study the effect of intensive cycling exercise, with an energy expenditure comparable to values derived from the Tour de France, on food and fluid intake, energy balance, nitrogen balance, and nutrient oxidation. Thirteen highly trained cyclists consuming a normal carbohydrate (CHO)-rich diet (60 En%) were studied during a 7-day stay in a respiration chamber. Two preparation days were followed by a standardized resting day (3), after which the subjects completed two exhausting exercise days (4-5). On day 6 the standardized resting day was repeated. Food and fluid intake were measured by weighed procedure. Energy expenditure was calculated from continuous gas analysis. Energy and nitrogen losses were calculated from all measured excretes. The results showed that energy balance (EB) and nitrogen balance (NB) were positive on the first resting day and became negative on the exercise days. EB was positive again on the recovery day whereas NB remained negative. Nitrogen losses almost balanced N intakes (1.7 g.kg-1) indicating an increased protein requirement. CHO oxidation exceeded CHO intake indicating endogenous CHO depletion. Contribution of CHO to energy exchange decreased from 51.4% +/- 3.1% on day 4 to 40.6% +/- 3.4% on day 5; this decrease was compensated by an increased fat oxidation. The food consumption pattern during days 4 and 5 was not different from days 2 and 6. In-between meal consumption accounted for 30.5%-34.3% of total energy intake. Fluid consumption was adequate to compensate for the losses.(ABSTRACT TRUNCATED AT 250 WORDS)

Eating, drinking, and cycling. A controlled Tour de France simulation study, Part II. Effect of diet manipulation.

Field studies during the Tour de France indicated that cyclists consume 30% of daily energy intake as liquid carbohydrate (CHO)-enriched nutrition with the goal of maintaining energy and CHO balance. The aim of the present investigation was to study the effect of such dietary manipulation during 2 days of long-lasting exhausting cycling on food and fluid intake, energy balance, nitrogen balance, and nutrient oxidation. Thirteen highly trained cyclists were divided into two subgroups receiving ad libitum either a primarily maltodextrin-based beverage (Mf) (20% w/v, 85% maltodextrin, 15% fructose) or a 50/50% composed fructose-maltodextrin (FM) beverage in addition to their normal diet. The study was performed during a 7-day stay in a respiration chamber (2 preparation days, 1 standardized resting day, 2 cycling days, 1.5 standardized recovery days), allowing for continuous gas analysis, weighed food and fluid intake procedure, and collection of excretes. The data of this study were compared with data from the same subjects receiving a normal CHO-rich diet (N) (60 En%) in a separate experiment. The results showed that the cyclists receiving Mf were able to maintain EB during sustained exercise days in contrast to when receiving N and to subjects receiving FM. With Mf treatment CHO intake increased, up to 80 En% (17.5 +/- 1.0 g.kg-1 BW) and carbohydrate balance remained positive. The subjects receiving FM had the largest CHO oxidation, calculated from R. Protein oxidation significantly increased in N and FM as a result of exercise but not in Mf. The latter subjects were in slightly negative nitrogen balance at a protein intake level of 1.4 g.kg-1 BW.(ABSTRACT TRUNCATED AT 250 WORDS)