HIGH GLYCEMIC INDEX FOOD

Abstract

PURPOSE: The purpose of this study was to examine the effects of feeding frequency on subsequent endurance capacity after prolonged, submaximal running during a short-term recovery. METHODS: Eight trained male runners completed two trials separated by at least ten days in a counterbalanced design. Each trial consisted of a 90-min run on a level treadmill at 70% VO2 max (R1) followed by 4-hr recovery (REC) and then a run to exhaustion at the same intensity as R1 (R2). Twenty minutes after R1 each subject consumed a prescribed meal with a glycemic index of 77 (2.4 íÓ 0.1 MJ, 65% CHO, 15% protein, and 20% fat) in either a ígorgingí (GOR) or ínibblingí (NIB) intake pattern. In the GOR trial the foods were consumed in a single bolus, whereas in the NIB trial the same amount of prescribed foods were equally divided into three portions and consumed by the subjects at hourly intervals. The prescribed foods provided 1.5 g CHO/kg body mass. During REC, subjects also ingested a prescribed volume of water equal to 150% of their body mass loss in R1. Results: The run times to exhaustion were similar between treatments (GOR vs NIB: 68.1 íÓ 8.2 vs 66.8 íÓ 8.7 min, NS, Effect Size = 0.06). The CHO oxidation rate throughout R2 in the GOR trial was lower than that in the NIB trial (p < 0.05), whereas the fat oxidation rate throughout R2 in the GOR trial was higher than that in the NIB trial (p < 0.05). A greater amount of fat was utilized during R2 in the GOR trial than in the NIB trial (GOR vs NIB: 55.9 íÓ 8.0 vs 44 íÓ 8.6 g, p < 0.01). After REC, subjects almost achieved complete rehydration on both occasions (GOR vs NIB: 98.5 íÓ 6.4 vs 95.7 íÓ 9.5%, NS). CONCLUSIONS: It was concluded that serial consumption of small amounts of CHO during a 4-hr recovery following prolonged, submaximal running increased the reliance on CHO oxidation for energy provision during a subsequent run, when compared to a single feeding. However, there was no difference in the duration of the exhaustive run following the recovery between the GOR and NIB trials.