Performance Effects of Carbohydrate Ingestion Between Bouts of Intense Aerobic Interval Exercise

This study tested whether CHO intake during a 2-h rest between exercise bouts improved performance in the subsequent bout.

In a randomized, single-blinded, crossover design, 10 recreationally-active participants (23 ± 4 yr, 70.8 ± 6.6 kg, VO_2peak:47.0 ± 5.4 mL O₂·min^-1·kg body mass^-1) arrived at the lab post-prandial and completed 2 exercise bouts separated by 2-h rest. Bouts included 5 x 4-min intervals at ~80% VO_2peak separated by 2-min at ~40% VO_2peak and ended with an endurance trial (ET) to voluntary exhaustion at ~90% VO_2peak. During intervals 1 and 4 in each bout expired gases were collected and O₂ deficit was estimated. Immediately following bout-1, either a CHO (1.2 g CHO·kg body mass^-1) or placebo (PL) solution was consumed.

ET duration decreased in bout-2 vs. 1 in both conditions (P<0.01) but was ~35% longer in bout-2 with CHO vs. PL (Interaction, P=0.03; post-hoc, P=0.03). VO₂ increased during interval 4 vs. 1 in both bouts (P<0.01) but was unaffected by CHO (P≥0.58). O₂ deficit was unaffected by CHO (P=0.93), bout or interval (P≥0.15). Perceived exertion was higher in bout-2 vs. 1 (P<0.001) and reduced in intervals 2 and 4 in CHO (P≤0.01).

When rest between training sessions is 2 hours, athletes may improve subsequent performance by consuming CHO during recovery. Supported by NSERC, Canada.