Effects of ingesting a sports bar versus glucose polymer on substrate utilisation and ultra-endurance performance

The purpose of this study was to determine whether the ingestion of a sports bar (BAR) containing a mixture of fat (7 g), protein (14g) and carbohydrate (CHO; 19g) improved ulta-endurance cycling performance compared to when an equicaloric amount of CHO was consumed. On two occasions separated by a minimum of 7 days, six highly trained (peak power output [PPO] 414+/-8W) endurance cyclists rode for 330 min at similar to 50% of PPO (203 +/- 8 W) while ingesting either the BAR or just CHO, before performing a 400 kj time trial as fast as possible. Rates of fat oxidation were significantly greater at the end of the submaximal ride when subjects ingested the BAR compared to CHO (1.09 +/- 0.08 vs 0.73 +/- 0.08 g min(-1); P < 0.05), and accordingly total fat oxidation was significantly higher (280+/-24 vs 203 +/- 25 g, P< 0.05). However, two subjects failed to complete the time trial after they consumed the BAR during the prolonged, submaximal ride; whereas all subjects managed to finish the time trial when ingesting CHO. In conclusion, ingestion of the sports bar enhanced fat metabolism during prolonged, submaximal exercise, but impaired subsequent high-intensity time-trial performance.