While effective for asthma patients, the use of beta-2 agonists is behind a sports controversy. Recently, a review and pooled data analysis of the available evidence published in the British Journal of Sports Medicine found that the drugs can boost sprint and strength performance in athletes without asthma.
Norwegian authors and colleagues suggest the performance-enhancing qualities of beta-2 agonists seem to be greater when used orally instead of inhaled. Furthermore, they note that it is unclear whether beta-2 agonists officially approved for use by the World Anti-Doping Agency (WADA) have the same effects as those that have been banned.
The study specifically looked at the effect of beta-2 agonists on anaerobic performance in healthy nonasthmatic subjects.
Four databases (PubMed, Embase, SPORTDiscus and Web of Science) were searched for randomized controlled trials, published until December 2019, examining the effect of beta-2 agonists on maximal physical performance lasting 1 minute or less. Data are presented as standardized difference in mean (SDM) with 95% confidence intervals (95% CI). Ultimately, 34 studies were included in the meta-analysis, including 44 different randomized and placebo-controlled comparisons with beta-2 agonists. The studies included 323 participants in crossover trials, and 149 participants in parallel trials.
Results in the overall analyses indicate that beta-2 agonists improved anaerobic performance by 5% (SDM 0.29, 95% CI, 0.16- 0.42), but the effect was related to dose and administration route. In a stratified analysis, the SDM was 0.14 (95% CI, 0.00-0.28) for approved beta-2 agonists and 0.46 (95% CI, 0.24-0.68) for prohibited beta-2 agonists, respectively.
The authors report that SDM was 0.16 (95% CI, 0.02-0.30) for inhaled administration and 0.51 (95% CI, 0.25-0.77) for oral administration, respectively; 0.20 (95% CI, 0.07-0.33) for acute treatment; and 0.50 (95% CI, 0.20-0.80) for treatment for multiple weeks. Strength (0.35, 95% CI, 0.15-0.55) and sprint (0.17, 95% CI, 0.06-0.29) performance were improved by beta-2 agonists, according to analyses stratified for the type of performance.
The article notes that this is “an improvement that would change the outcome of most athletic competitions,” amounting to 3% for sprint performance and 6% for strength performance.
“Our study shows that non-asthmatic subjects can improve sprint and strength performance by using beta-2 agonists,” the authors write. “It is uncertain, however, whether World Anti-Doping Agency (WADA)-approved doses of beta-2 agonists improve performance. Our results support that the use of beta-2 agonists should be controlled and restricted to athletes with documented asthma.”
Earlier this year, WADA updated its list of banned substances, which included all beta-2 agonists except specific doses of inhaled salbutamol, formoterol, and salmeterol.
When the analysis was further refined to a comparison of banned and approved beta-2 agonists, the approved drugs didn’t significantly boost anaerobic performance, while banned beta-2 agonists did.
Yet the authors say they still found a tendency towards enhanced performance for approved beta-2 agonists, and the effect was even greater after several weeks of treatment.
“This means that it is still uncertain whether approved doses improve anaerobic performance,” the researchers write.
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