Pseudoephedrine Ingestion and Exercise Performance

Kellie Pritchard-Peschek (2011). Pseudoephedrine Ingestion and Exercise Performance PhD Thesis, School of Human Movement Studies, The University of Queensland.

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Author Kellie Pritchard-Peschek
Thesis Title Pseudoephedrine Ingestion and Exercise Performance
School, Centre or Institute School of Human Movement Studies
Institution The University of Queensland
Publication date 2011-03
Thesis type PhD Thesis
Supervisor Associate Professor David Jenkins
Dr Mark Osborne
Dr Gary Slater
Professor Dennis Taaffe
Total pages 152
Total black and white pages 152
Language eng
Subjects 11 Medical and Health Sciences
Abstract/Summary The primary aims of the four studies that comprise the present thesis were to evaluate the potential for pseudoephedrine supplementation to improve prolonged high intensity cycling performance and assess the corresponding physiological responses, with a view to elucidating potential mechanisms of action. In the first study (Study One), the prevalence of pseudoephedrine use among elite Australian athletes was assessed. One hundred and eighty-four elite Australian athletes from amateur (swimming, rowing, BMX cycling, hockey, water polo and triathlon) and professional sports (rugby league, rugby union and Australian football) were surveyed on prevalence of use, knowledge and attitudes relating to pseudoephedrine use in sport. It was found that 23 athletes (12.5%) from the various sports admitted to having used pseudoephedrine to enhance their performance, with rugby league players (NRL) reporting the highest use compared to all other sports (43.5%, p = 0.009). Eighty percent of these athletes used a pseudoephedrine dose unlikely to elicit a performance effect. Moreover, only 42% of the athletes surveyed were aware that pseudoephedrine is presently on the 2010 World Anti-Doping Agency’s (WADA) prohibited substance list. Study Two investigated the effect of a 180 mg pseudoephedrine dose on high intensity cycling time trial performance. Six trained male cyclists and triathletes completed two cycling time trials of ~30 minutes duration - one under each condition of 180 mg of pseudoephedrine or placebo consumed in random order 60 minutes prior to the start of exercise. Blood was collected pre- and post-exercise for the later analysis of glucose, lactate, pH and the catecholamines. The ingestion of 180 mg of pseudoephedrine improved cycling time trial performance by 5.1% compared to placebo (28:58.9 ± 4:26.5 min; 30:31.7 ± 4:36.7 min, p = 0.05). Pseudoephedrine ingestion elicited a significant increase (p = 0.04) in norepinephrine concentration post-exercise compared to the placebo trial; a trend (p = 0.06) for increased blood glucose concentration in response to pseudoephedrine was also found. Study Three examined a possible dose-response between pseudoephedrine and high intensity, prolonged exercise. On three occasions, 10 trained male cyclists and triathletes performed the same cycling time trial as that used in Study Two; 2.3 mg•kg-1 body mass (BM), 2.8 mg•kg-1 BM of pseudoephedrine or placebo was consumed 60 minutes prior to the start of exercise. Blood was sampled at baseline and pre- and post-exercise for the later analysis of plasma pseudoephedrine concentrations in addition to lactate, glucose and catecholamine concentrations. In contrast to the findings of Study Two, neither pseudoephedrine dose significantly improved cycling time trial performance compared to placebo (p = 0.60). Large inter-individual variations in plasma pseudoephedrine concentration were found between participants. It was concluded that pre-exercise differences in plasma pseudoephedrine concentrations between individuals following pseudoephedrine ingestion may explain, in part, inconsistencies in performance found between investigations. In light of the findings from Study Three, the purpose of the final study (Study Four) was to increase the period between pseudoephedrine intake and the start of exercise so that exercise was more likely to coincide with peak plasma pseudoephedrine concentrations. Ten trained male cyclists and triathletes completed four cycling time trials (~30 minutes), in which they were randomised to a “fed” or “fasted” condition, and ingested either 2.8 mg•kg-1 BM of pseudoephedrine or placebo 90 minutes prior to the start of exercise. Venous blood was sampled in the initial 90 minute absorption period, at baseline and pre- and post-exercise for plasma pseudoephedrine concentration and metabolic markers, to potentially elucidate possible mechanisms of action of pseudoephedrine. Consistent with the findings from Study Three, the ingestion of 2.8 mg•kg-1 BM of pseudoephedrine, independent of the consumption of food, did not influence cycling time trial performance of ~30 minutes duration. The co-ingestion of a pre-exercise meal with pseudoephedrine resulted in lower plasma concentrations at 50 min, 70 min, pre-warm up and post-exercise compared to the fasted condition. Despite prolonging the absorption period following pseudoephedrine intake, the time trial did not coincide with peak plasma pseudoephedrine concentrations. Norepinephrine concentration was significantly elevated post-exercise in response to pseudoephedrine compared to placebo; additionally, norepinephrine and epinephrine concentration post-exercise were significantly related to post-exercise lactate concentration. However, there was no relationship between these variables and exercise performance. The present series of investigations have shown that Australian athletes currently use pseudoephedrine to improve their performance with little knowledge of its legal status or its ergogenic effects. Although Study Two found that high intensity cycling performance significantly improved following the ingestion of a high dose (180 mg) of pseudoephedrine, this finding was not confirmed in Studies Three and Four. Pre- and post-exercise plasma pseudoephedrine concentrations found in these subsequent investigations showed considerable differences in the absorption and uptake of pseudoephedrine, and its peak plasma concentrations between participants. That the significant increases in post-exercise norepinephrine in response to pseudoephedrine were unrelated to exercise performance suggests that there may be additional (e.g., central) factors contributing to pseudoephedrine‘s potential to influence exercise capacity.
Keyword Sympathomimetic
Ergogenic aid
Plasma concentration
Additional Notes Colour pages: 0 Landscape pages: 33-34, 152.

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Created: Wed, 09 Nov 2011, 21:20:53 EST by Ms Kellie Pritchard-peschek on behalf of Library - Information Access Service