Assessment of the impact of selected dietary supplements on endurance ability in high-temperature environments
Date
2019-10-07
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Abstract
Toidulisandite kasutamine kehalise töövõime ja kognitiivse võimekuse parandamiseks on laialdaselt levinud sportlaste seas, aga ka rahvastikus laiemalt. Paraku on kontroll toidulisandite tootmise üle nõrk ning tõenduspõhine teave turul pakutavate toodete toime ja ohutuse kohta napp. Nii otsustatakse toidulisandite kasutamise üle sageli info põhjal, millel puudub teaduslik taust.
Kofeiini kui toidulisandi vastupidavuslikku töövõimet parandav mõju on teaduslikult tõendatud. Naatriumtsitraadi toimet on uuritud vähe ja senised andmed on vastuolulised. Samas inimese organismi reaktsioon kehalisele koormusele, aga ka toidulisandite toime, sõltuvad keskkonnateguritest. Senised teadmised kofeiini, eriti aga naatriumtsitraadi toime kohta pärinevad valdavalt normaalsetes keskkonnatingimustes tehtud uuringutest. Käesoleva uurimistöö peamiseks eesmärgiks oli välja selgitada nende manustamise mõju treenitud indiviidide vastupidavuslikule töövõimele kõrge temperatuuriga keskkonnas.
Kofeiini uuringus kõndisid noored mehed ja naised pärast kofeiini või platseebo manustamist jooksulindil kõrge temperatuuriga (42 °C) kuivas (suhteline õhuniiskus 20%) keskkonnas suutlikkuseni. Naatriumtsitraadi uuringus, mis teatud määral imiteeris jalgratturite mitmepäevavõistlust kõrge temperatuuriga keskkonnas (32 °C; suhteline õhuniiskus 46%), pedaalisid treenitud mehed veloergomeetril esmalt 4%-lise kehakaalu languseni. Pärast 16 h taastumisperioodi koos naatriumtsitraadi või platseebo manustamisega läbiti samades keskkonnatingimustes 40 km aja peale.
Kumbki manustatud toidulisanditest võrreldes platseeboga vastupidavuslikku töövõimet ei parandanud. Kofeiin vähendas pingutuse subjektiivselt tajutud raskusastet ja väsimuse taju meestel, aga mitte naistel. Kofeiini mõjul suurenes südame löögisagedus ja ilmnes ulatuslikum laktaadi taseme tõus veres, kuid keha soojusregulatsiooni kofeiin ei mõjutanud. Naatriumtsitraat stimuleeris organismi veestaatuse normaliseerumist ja vereplasma mahu suurenemist, kuid ei mõjutanud pingutuse subjektiivselt tajutavat raskusastet järgnenud 40 km ajasõidul. Keha süvatemperatuur ning kortisooli ja aldosterooni tase veres 40 km ajasõidu lõpus osutusid naatriumtsitraadi kasutamisel võrreldes platseeboga madalamaks.
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.
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.
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Keywords
kehaline töövõime, vastupidavus, temperatuuri toime, toidulisandid, kofeiin, naatriumiühendid, füsioloogiline kohanemine, spordifüsioloogia