Abstract
We investigated whether fitness and bovine colostrum supplementation modulates cognition and cerebrovascular function during exercise in the heat in this placebo-controlled, double-blind study. Seven highly-fit (HF, (V) over dotO(2peak) 64 +/- 4 mL kg(-1) min(-1)) and eight moderately-fit (MF, 46 +/- 4 mL kg(-1) min(-1)) men completed two randomised, 90-min exercise bouts (30 degrees C, 50% RH) after 7-d of bovine colostrum supplementation (COL: 1.7 g kg(-1) d(-1)) or placebo (CON: cornflour). Multi-mode exercise consisted of: 15-mm fixed-load cycling at 50% heart rate reserve (HRR; Cycle1), 30-min fixed-speed running (80% HRR; Run1), 30-min time trial (Run2), then repeating cycling (Cycle2). Heart rate, end-tidal PCO2, cerebral oxygenation, a marker of blood-brain barrier integrity ([S100 beta]), cognition (Stroop test) and perceptions were recorded at rest, Cycles1 and 2, and 5 h post-exercise. MF had less cerebral deoxygenation during exercise (MF: -5 +/- 14, HF: 8 +/- 7 mu M L-1), but [S100 beta] was unchanged across fitness and colostrum supplementation. Hypocapnia was evident from Cycle1 to Run2 with end-tidal PCO2 decreasing from 36 +/- 5 to 31 +/- 5 mmHg in both trials. Response time to simple and complex tasks decreased during exercise by similar to 83 and similar to 301 ms, compared to rest in both fitness groups in both trials. The time difference between complex and simple tasks (i.e. decision-making time) also decreased from 724 +/- 200 (Rest) to 552 +/- 326 (Cycle1), 565 +/- 148 (Cycle2) and 515 +/- 216 ms (post-exercise; pooled results). We conclude that fitness per se does not modulate cognitive executive function or blood-brain barrier permeability during comparable, relative-intensity exercise in the heat, and that colostrum supplementation had negligible effect on performance, cognitive or cerebrovascular functioning. (C) 2013 Elsevier Ltd. All rights reserved.