On 8 November at 12 Silva Suvi will defend her doctoral thesis „Assessment of the impact of selected dietary supplements on endurance ability in high-temperature environments“.
Professor Vahur Ööpik, Professor of Exercise Physiology, University of Tartu
Professor Ronald J. Maughan, School of Medicine, St Andrews University, Great Britain
Dietary supplements are widely used by athletes with the aim of improving physical and cognitive performance and this practice has increasingly spread among general population. However, the production of dietary supplements is loosely regulated and there is insufficient evidence-based information on the effect and safety of the marketed products. The intake of dietary supplements is thus often decided solely on the basis of information that lacks any scientific background. There is research-based evidence that caffeine as dietary supplement improves endurance ability. Current data on the effect of sodium citrate are scarce and the study results have been controversial. Both the reaction of the human organism to exercise and the effect of dietary supplements depend on environmental factors. However, the knowledge on the effect of caffeine, and especially sodium citrate has been obtained from the studies carried out predominantly in normal environmental conditions. The main aim of this research was to determine the impact of their administration on endurance ability of trained individuals in high-temperature environments. In caffeine study, young men and women were administered either caffeine or placebo, and then walked on treadmill to exhaustion in high-temperature (42 °C) dry (relative humidity 20%) environment. The study concerning sodium citrate imitated to some extent multi-stage cycling competitions in high-temperature environment (32 °C; relative humidity 46%): trained men exercised on cycle ergometer until they lost 4% of body mass. Following the 16 h recovery period, including the administration of either sodium citrate or placebo, the subjects cycled in the same environmental conditions 40-km as fast as possible. Neither of the administered dietary supplements improved endurance ability, compared to placebo. Caffeine decreased ratings of perceived exertion and fatigue in males, but not in females. Caffeine induced greater increases in heart rate and blood lactate concentrations, but did not have any impact on thermoregulation. Sodium citrate enhanced rehydration and increased blood plasma volume, but did not have any impact on the ratings of perceived exertion during the 40-km time-trial. The core body temperature and the level of cortisol and aldosterone in blood at the end of 40-km time-trial occurred to be lower in case of sodium citrate administration compared to placebo.