RUNNING PERFORMANCE IN HOT, HUMID CONDITIONS: EFFECT OF BEVERAGE CARBOHYDRATE CONTENT 1197

Abstract

In an attempt to determine the influence of beverage carbohydrate content on running performance during prolonged exercise in the heat, 10 well-trained male runners were studied. The mean age, height, weight, VO2max, and% body fat were 37.2±3.1 yrs, 177.2±2.1 cm, 73.5±2.6 kg, 61.2±2.6 ml·kg1·min-1, and 12.2%, respectively. Subjects completed four 15 mile treadmill runs in an environmental chamber maintained at 80°C and 70%RH. The first 12 miles of each run was paced at 70% VO2max, and the final 3 miles was considered a time-trial. For all runs, subjects consumed 400 ml of a designated carbohydrate electrolyte (CE) beverage prior to running, and 200 cc at 3 mile intervals. The first run was considered a familiarization trial, and subsequent trials were randomized and counterbalanced such that subjects consumed one of three CE drinks (6%, 8%, and 10% C, with 5% HFCS and balance as maltodextrin, with 10mM Na+, 3.3 mM K+, and 5.4 mM CL-). Mean 3 mile run time was 41.3 seconds (3.5%) faster on 6% CE vs. 10% CE and 37.8 seconds (3.2%) faster on 8% CE vs. 10% CE (p=0.09 for both). Analysis of 0.5 mile split times demonstrated that the final split was run 14 seconds (7%) faster on 6% CE vs. 10% CE and 9.4 seconds (4.7%) faster on 8% CE vs. 10% CE (p=0.06). Taken together, these results suggests that consumption of a 10% CE beverage may impair performance relative to CE beverages with lower carbohydrate content.