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Effect of diet manipulation on metabolic changes and performance in competitive cyclists
Author(s) -
Brouns F.,
Saris W. H. M.,
Hoor F.
Publication year - 1991
Publication title -
journal of human nutrition and dietetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.951
H-Index - 70
eISSN - 1365-277X
pISSN - 0952-3871
DOI - 10.1111/j.1365-277x.1991.tb00079.x
Subject(s) - glycogen , medicine , endocrinology , fructose , carbohydrate , glucagon , insulin , carbohydrate metabolism , zoology , food science , biology
Thirteen highly trained subjects were studied for the effect of consuming a normal carbohydrate‐rich diet (N) on energy exchanged, substrate metabolism and performance. Six of these subjects performed the same protocol receiving N supplemented with a high maltodextrin‐low fructose beverage (Mf). The studies were performed in random order. The subjects performed two days of sustained exhausting cycling, proceeded and followed by a standardized resting day, in a respiration chamber allowing for continuous gas analysis, weighed food and fluid intake, collection of excreta and drawing of blood samples at 07.00 hours, 12.00 hours (halfway exercise) and 15.00 hours at exhaustion. Muscle biopsies were taken prior to, 45 min after and 24 h after exercise (energy expenditure 25.2–26.6 MJ/day). The results showed that while consuming a normal diet, the cyclists develop a negative energy balance (‐9 MJ/day) and regulate their hormone levels in such a way that fat oxidation and protein breakdown are increased and CHO oxidation becomes depressed. When supplemented with Mf the subjects showed increased blood glucose, insulin and decreased glucagon levels. Fat metabolism was significantly depressed as indicated by the levels of blood fatty acids, glycerol and ketones. A significant glycogen sparing, as well as supercompensation within 24 h of recovery, was observed after Mf supplementation. The normal ad libitum available CHO‐rich diet was insufficient fully to restore glycogen within 24 h. The changes in substrate availability and glycogen depletion were accompanied by a significant performance improvement, 126% when cycling a final 90% Wmax bout, when supplemented with Mf compared to N.