Effects of Pseudoephedrine on Maximal Cycling Power and Submaximal Cycling Efficiency

H. HODGES, ALASTAIR N.; LYNN, BRENNA M.; BULA, JONATHAN E.; DONALDSON, MEGHAN G.; DAGENAIS, MARC O.; MCKENZIE, DONALD C.

Medicine & Science in Sports & Exercise: August 2003 - Volume 35 - Issue 8 - pp 1316-1319
BASIC SCIENCES: Original Investigations

HODGES, A. N. H., B. M. LYNN, J. E. BULA, M. G. DONALDSON, M. O. DAGENAIS, and D. C. MCKENZIE. Effects of Pseudoephedrine on Maximal Cycling Power and Submaximal Cycling Efficiency. Med. Sci. Sports Exerc., Vol. 35, No. 8, pp. 1316–1319, 2003.

Purpose: To study the effects of a therapeutic dose of pseudoephedrine on anaerobic cycling power and aerobic cycling efficiency.

Methods: Eleven healthy moderately trained males (V̇O2peak 4.4 ± 0.8 L·min−1) participated in a double-blinded crossover design. Subjects underwent baseline (B) tests for anaerobic (Wingate test) and aerobic (V̇O2peak test) cycling power. Subjects ingested either 60 mg of pseudoephedrine hydrochloride (D) or a placebo (P) and, after 90 min of rest, a Wingate and a cycling efficiency test were performed. During the cycling efficiency test, heart rate (HR) and V̇O2 were averaged for the last 5 min of a 10-min cycle at 40% and 60% of the peak power achieved during the V̇O2peak test.

Results: There were no significant differences in peak power (B = 860 ± 154, D = 926 ± 124, P = 908 ± 118 W), total work (B = 20 ± 3, D = 21 ± 3, P = 21 ± 3 kJ), or fatigue index (B = 39 ± 8, D = 45 ± 5, P = 43 ± 5%). There were no significant differences in HR at 40% power (D = 138 ± 10, P = 137 ± 10 beats·min−1) or 60% power (D = 161 ± 11, P = 160 ± 11 beats·min−1). There were no significant differences in cycling efficiency at 40% power (D = 18.8 ± 1.8, P = 18.5 ± 1.8%) or 60% power (D = 20.3 ± 2.0, P = 20.1 ± 2.1%).

Conclusion: A therapeutic dose of pseudoephedrine hydrochloride does not affect anaerobic cycling performance or aerobic cycling efficiency.

Pseudoephedrine is a sympathomimetic drug commonly found in nonprescription cold and flu medications. It is clinically useful in the treatment of mucosal congestion accompanying hay fever, allergic rhinitis, sinusitis, and other respiratory conditions. Pseudoephedrine is an α1 and β1 agonist similar in structure to ephedrine and amphetamines, and is listed as a banned substance by the International Olympic Committee for its classification as a stimulant. This drug has resulted in several positive drug tests in international athletic competitions in recent years. Cold and flu medications that do not contain pseudoephedrine are generally acceptable for athletes in international competition. Thus, its role as a possible ergogenic aid restricts the general clinical use of pseudoephedrine containing medications by athletes. Pseudoephedrine acts to increase heart rate (HR) and cardiac contractility. It is these chronotropic and inotropic effects that may lead to abuse of this drug during competition in an effort to attain an ergogenic effect. However, a therapeutic dose of pseudoephedrine, for treatment of mucosal congestion, should be considered separately than much greater doses used intentionally for ergogenic gain.

Although several studies have shown some increase in performance with the use of ephedrine and/or caffeine (1–3,5), there is very limited evidence of an ergogenic effect from pseudoephedrine. It has been shown that pseudoephedrine is without ergogenic effects during prolonged high-intensity exercise (9), during time to exhaustion tests (16), and during an incremental exercise test to exhaustion (6) and has limited ergogenic properties during a 30-s “all-out” cycle test (8). Thus, we saw a need to examine the effects of pseudoephedrine on two types of exercise: 1) maximal anaerobic exercise applicable to short-duration or intermittent high-intensity sport performance and 2) submaximal efficiency applicable to long-duration continuous sport performance.

The aim of the current investigation was to examine the effects of a therapeutic dose of pseudoephedrine on applied exercise performance, and for this reason, the following considerations were instrumental in the development this study. The normal therapeutic dose of 60-mg pseudoephedrine was used in this study as an appropriate representation of the dose typically taken by athletes in an attempt to treat symptoms from a common cold or flu. Although anaerobic cycle tests have been shown to be reliable, there is some debate as to what they measure. According to Inbar et al. (10), there is lack of agreement on the terminology used to describe the output of anaerobic tests. Nevertheless, peak power and total work are objective measures that may be compared between subjects and conditions. It is for this reason, and because the Wingate is the most commonly used anaerobic ergometric test, that the Wingate was used in this study. Efficiency of human muscle contraction has been defined as the ratio of energy output to energy consumption (12). Gross efficiency does not distinguish between energy consumption related to the work performed and basal energy consumption, and was calculated as the ratio of work output to total energy consumption (7,14,15).

Allan McGavin Sports Medicine Centre and School of Human Kinetics, University of British Columbia, Vancouver, British Columbia, CANADA

Address for correspondence: Donald C. McKenzie, Allan McGavin Sports Medicine Centre and School of Human Kinetics, University of British Columbia, 3055 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada; E-mail: kari@interchange.ubc.ca.

Submitted for publication April 2002.

Accepted for publication February 2003.

©2003The American College of Sports Medicine