The effect of a preexercise meal on time to fatigue during prolonged cycling exercise

Purpose and Methods: Seven subjects exercised to exhaustion on a bicycle er gometer at a workload corresponding to an intensity of 70% maximal oxygen u ptake ((V) over dot O-2max). On one occasion (FED), subjects consumed a pre exercise carbohydrate (CHO) containing breakfast (100 g CHO) 3 h before exe rcise. On the other occasion (FASTED), subjects exercised after an overnigh t fast. Exercise time to fatigue was significantly longer (P < 0.05) when s ubjects consumed the breakfast (136 +/- 14 min) compared with when they exe rcised in the fasted state (109 +/- 12 min). Results: Pre- and post-exercis e muscle glycogen concentrations,respiratory exchange ratio, carbohydrate a nd fat oxidation, and lactate and insulin concentrations were nor significa ntly different between the two trials,Insulin concentrations decreased sign ificantly (P < 0.05) from 4.7 +/- 0.05 mu IU.mL(-1) to 2.8 +/- 0.4 mu IU.mL (-1) in FED and from 6.6 +/- 0.6 mu IU.mL(-1) to 3.7 +/- 0.6 mu IU.mL(-1) i n FASTED subjects and free fatty acid concentrations (FFA) increased signif icantly (P < 0.05) from 0.09 +/- 0.02 mmol.L-1 to 1.4 +/- 0.6 mmol.L-1 in F ED and from 0.17 +/- 0.02 mmol.L-1 to 0.74 +/- 0.27 mmol.L-1 in FASTED subj ects over the duration of the trials. Conclusions: Tn conclusion, the impor tant finding of this study is the increased, time to fatigue when subjects ingested the CHO meal with no negative effects ascribed to increased insuli n concentrations and decreased FFA concentrations after CHO ingestion.