MUSCLE GLYCOGEN-STORAGE AFTER PROLONGED EXERCISE - EFFECT OF THE FREQUENCY OF CARBOHYDRATE FEEDINGS

We reported previously that intake of carbohydrate foods with a high g lycemic index (GI) produced greater glycogen storage and greater postp randial glucose and insulin responses during 24 h of postexercise reco very than did intake of low-GI carbohydrate foods. In the present stud y we examined the importance of the greater incremental glucose and in sulin concentrations on glycogen repletion by comparing intake of larg e carbohydrate meals (''gorging'') with a pattern of frequent, small, carbohydrate snacks (''nibbling''), which simulates the flattened gluc ose and insulin responses after low-GI carbohydrate meals. Eight well- trained triathletes [(x) over bar +/- SEM: 25.6 +/- 1.5 y of age, weig hing 70.2 +/- 1.9 kg; and with a maximal oxygen uptake (VO(2)max) of 4 .2 +/- 0.2 L/min] undertook an exercise trial (2 h at 75% VO(2)max fol lowed by four 30-s sprints) to deplete muscle glycogen on two occasion s, 1 wk apart. For 24 h after each trial, subjects rested and consumed the same diet composed exclusively of high-GI carbohydrate foods, pro viding 10 g carbohydrate/kg body mass. The ''gorging'' trial provided the food as four large meals of equal carbohydrate content eaten at 0, 4, 8, and 20 h of recovery, whereas in the ''nibbling'' trial each of the meals was divided into four snacks and fed at hourly intervals (0 -11, 20-23 h). However, there was no significant difference in muscle glycogen storage between the two groups over the 24 h (gorging: 74.1 /- 8.0 mmol/kg wet wt; nibbling: 94.5 +/- 14.6 mmol/kg wet wt). The re sults of this study suggest that there is no difference in postexercis e glycogen storage over 24 h when a high-carbohydrate diet is fed as s mall frequent snacks or as large meals, and that a mechanism other tha n lowered blood glucose and insulin concentrations needs to be sought to explain the reduced;rate of glycogen storage after consumption of l ow-GI carbohydrate foods.