Comparison of 6% Carbohydrate and Caffeinated Soda Beverage Consumption during Half-marathon Treadmill Time-trials

Abstract

For optimal performance in longer (>90 min) endurance events, adequate fluid and carbohydrate intake is often advised. Plain water or 6% carbohydrate-electrolyte beverage (6% CHO-E) are often the choices offered at running races. Defizzed, caffeinated, cola beverages (11% CHO-CAF) are also used during the later stages of ultra endurance events and research has demonstrated a performance benefit (Cox et al, 2002). However, during running races, especially higher intensity events, gastro-esophageal and intestinal distress may be more frequent than during cycling. PURPOSE: To determine whether caffeinated cola intake would lead to a decrement in endurance running performance. METHODS: Ten runners (3F/7M; age = 31±12; VO2max = 57±7) performed 3 self-paced, 21.1km treadmill time trials (1% grade). Subjects were non-fasted and prepared for the trials as they would for a race. They were instructed to complete the 21.1km as fast as possible, were blinded to current pace, but were given mile times. Water (W) was offered ad libitum during the first trial, which served as a familiarization trial and allowed estimation of preferred water intake. Trials 2 and 3 were randomized for 6% CHO-E or 11% CHO-CAF solutions. Forty min prior to each run, subjects consumed 500ml of the beverage for that trial; thereafter 150ml was consumed at 1.6, 4.8, 8.0, 11.2, 14.4, and 17.6km. Weight loss, performance time, and mile pace were recorded. Oxygen consumption (VO2), respiratory exchange ratio (RER), ratings of stomach fullness (RSF) and perceived exertion (RPE) were collected throughout the run. RESULTS: There were no significant differences in performance time between trials (W= 1:42:42 ±13:34; 11%CHO-CAF= 1:39:42 ± 14:39; 6% CHO-E = 1:40:43 ± 14:30). Mean weight loss tended to be greatest during W trial (2.6 ± 0.7% of body weight) due to lower consumption (561 ± 321ml vs 900ml). Weight loss exceeded 3% body weight in 2 subjects during W trials and in 1 subject during 11% CHO-CAF. During the run, mean RSF was highest for 11% CHO-CAF (3.7 ± 0.7), lowest in W (2.7 ± 0.8) and tended to increase during both CHO trials. RPE increased throughout the run but did not differ significantly between trials. VO2 and RER did not differ between 6% CHO-E and 11 % CHO-CAF. A tendency for runners to start faster during 11 % CHO-CAF compared with 6% CHO-E was noted (difference for first 1.6km = 23.5 ±40.5 sec; p = 0.1). CONCLUSIONS: During self-paced 21.1km treadmill time trials, consumption of a caffeinated cola beverage resulted in significantly greater ratings of stomach fullness when compared with either water or 6% CHO-E beverage. In spite of this effect, running performance time for a half-marathon did not suffer.