Lemongrass Supplementation During Endurance Exercise May Compensate for Reduced Carbohydrate Intake

Abstract

Acute carbohydrate (CHO) supplementation has consistently been shown to positively affect prolonged (> 60–90 min) moderate intensity endurance performance. In addition to substrate availability, prolonged endurance performance may be influenced by central fatigue as reflected by ratings of perceived exertion (RPE). Central fatigue may be mediated by cognitive and physiological factors such as motivation and endogenous opioids, respectively. Endogenous opioids are released during exercise and have been shown to decrease RPE, but to our knowledge no study to date has investigated the effects of supplementation designed to increase endogenous opioid activity on exercise performance and RPE. Lemongrass (cymbopogon citratus) has been shown to have antinoceceptive effects, possibly mediated by enhanced endogenous opioid activity. PURPOSE: To compare the effects of sports drinks without (CO) and with lemongrass (LG) on exercise performance and RPE. METHODS: Following a familiarization trial, 10 experienced male cyclists (25 ± 5 yr, 51.2 ± 5.7ml/kg/min VO2peak) completed two 40-km time trials on a cycle ergometer while consuming the CO and LG drinks in randomized order and double-blind fashion. The time trials were separated by a week and the CO and LG drinks consisted of 6 and 3% CHO, respectively. Subjects consumed 250 mL of the assigned drink immediately prior to and at each 20% completed segment (∼ every 15 min) throughout the test. Subjects were instructed to provide a maximal sprint effort over the final 1 km of the time trial. Time, power, speed, RPE and HR were recorded at each 20% completed segment. RESULTS: Subjects rode at approximately 82% of maximal HR during the time trials. No significant differences were found between the CO and LG drinks in total time (74.1 ±3.7 vs. 74.6 ±3.6 min), power (189.4 ±25.4 vs. 185.7 ± 25.4 W), speed (31.1 ± 3.8 vs. 32.3 ± 1.6km/h), HR(153 ± 11 vs. 151 ± 13 b/pm), or RPE (13.4 ± 1.0 vs. 12.9 ± 0.8). Similarly, there were no significant differences between drinks in any of the measured variables at any of the 20% completed segments or the final 1-km sprint. CONCLUSION: Lemongrass supplementation during endurance exercise may compensate for reduced CHO intake, but does not appear to do so by reducing RPE.