salbutamol

Salbutamol: Ergogenic effects of salbutamol

The International Olympic Committee’s high index of suspicion over the use of inhaled beta2- adrenergic agonists for the prevention and treatment of exercise-induced asthma is fully justified, if the results of a new study from the Netherlands are anything to go by.

This study of the effects of supra-therapeutic doses of inhaled salbutamol on endurance cycling in non-asthmatic athletes found the drug enhanced performance to a significant degree – enough to give users a real advantage in competitive events.

In a double-blind, randomised cross-over study, 16 athletes performed two trials – at least four days apart – in which they had to perform a certain amount of work as fast as possible on a cycle ergometer, 30 minutes after inhaling either 800µg salbutamol or placebo. In the second trial the conditions were reversed, with those taking placebo switched to the active drug, and vice versa. Performance times were recorded and a range of blood and respiratory measurements were taken before and after exercise.

The most important finding was that average performance time on salbutamol was reduced by 82.7 seconds – 3,927.6 seconds (65 minutes), compared with 4,010.2 seconds, a difference of just under 2%. As the researchers point out: ‘The relevance of a more than 1-minute improvement in an approximately 1-hour time trial for competitive events is obvious.’

They can offer no explanation for this increase in performance, which was not explained by changes in plasma concentrations of free fatty acids, glycerol, lactate and potassium during exercise, or by changes in ventilatory parameters at rest and after exercise.

The significance of the study is that it is the first to show that inhalation of a supra-therapeutic dose of salbutamol improves time trial performance in non-asthmatic athletes, with previous studies showing no effects on endurance performance.

Why, then, did this one produce a positive result? The researchers suggest that their protocol for measuring endurance performance – performing a given amount of work as fast as possible – may be more sensitive than the time-to-exhaustion tests used in previous trials. Additionally, it seems that at the end of this type of trial subjects perform a ‘finishing kick’ which is absent during time-to-exhaustion tests.

‘It is possible,’ they conclude, ‘that salbutamol specifically improves this finishing kick.’

Int J Sports Med 2004;25:533-538

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