{"id":9499,"date":"2020-10-03T06:00:20","date_gmt":"2020-10-03T05:00:20","guid":{"rendered":"https:\/\/blogs.bmj.com\/bjsm\/?p=9499"},"modified":"2020-09-28T10:09:57","modified_gmt":"2020-09-28T09:09:57","slug":"%ce%b22-agonists-may-boost-strength-and-sprint-performance-whilst-endurance-seems-unaffected","status":"publish","type":"post","link":"https:\/\/blogs.bmj.com\/bjsm\/2020\/10\/03\/%ce%b22-agonists-may-boost-strength-and-sprint-performance-whilst-endurance-seems-unaffected\/","title":{"rendered":"\u03b22-agonists may boost strength and sprint performance, whilst endurance seems unaffected"},"content":{"rendered":"
Part of the BJSM’s #KnowledgeTranslation blog series<\/em><\/strong><\/h5>\n

In the following blog we summarise the main finding of our two recent papers examining the effect of \u03b22-agonists on physical performance1,2<\/sup>. We found that \u03b22-agonists may improve anaerobic but not aerobic performance in healthy athletes. <\/strong><\/p>\n

Asthma is common in top athletes3<\/sup> and \u03b22-agonists are often prophylaxis for exercise induced bronchial constriction (EIB), and as a reliever for symptoms4<\/sup>. Asthmatic athletes have consistently outperformed their non-asthmatic peers5<\/sup>, and this has led to speculation regarding a possible performance enhancing effect of \u03b22-agonists. Thus, the World Anti-Doping Agency (WADA) have banned the use of all \u03b22-agonists (apart from the use of some \u03b22-agonists inhaled in low doses6<\/sup>).<\/p>\n

Numerous studies have investigated the effect of different types, doses, administration routes and treatment durations of \u03b22-agonists on various types of maximal physical performance and the results have been conflicting. Therefore, we wanted to systematically review and meta-analyse these studies to investigate new and more complete patterns in the effect of \u03b22-agonists on physical performance in healthy athletes.<\/p>\n

Meta-analysis of randomised controlled trials<\/strong><\/p>\n

We screened four scientific databases for randomised controlled trials assessing the effect of \u03b22-agonists on maximal physical performance and assessed bias according to the recommendations from the Cochrane Collaboration. We categorised \u03b22-agonists according to type, dose, administration routes and treatment durations. The primary outcomes were anaerobic performance and aerobic performance. Anaerobic performance was subcategorised into strength, power and sprint performance, and aerobic performance was subcategorised into maximal oxygen uptake (VO\u00ad2max<\/sub>) and physical aerobic performance. We performed meta-analyses with meta regression.<\/p>\n

Different effects on anaerobic and aerobic performance<\/strong><\/p>\n

We found 81 studies comprising 1152 participants, finding no difference in effect between studies with high and low risk of bias.<\/p>\n

Overall \u03b22-agonists improved anaerobic performance by 5%. In stratified analyses both sprint performance and maximal muscular strength were improved by \u03b22-agonists. When we assessed the effect of doses approved and prohibited by WADA separately, prohibited doses improved anaerobic performance or strength and sprint performance analysed separately. Approved doses did not improve anaerobic performance or sprint and strength performance (Infographic 1). However, there was a tendency towards improved anaerobic performance also by WADA approved doses (p=0.051).<\/p>\n

\"\"<\/p>\n

Infographic 1: The effect of \u03b22-agonists on strength and sprint performance stratified by dose. (If the whiskers cross the dotted line the effect is zero)<\/small><\/p>\n

Aerobic performance was not affected by the use of \u03b22-agonists in the overall analysis or any analysis examining the effect of dose, type, administration routes or treatment durations on aerobic performance or when aerobic performance was divided into physical performance, time trial performance, time to exhaustion or VO\u00ad2max<\/sub> (Infographic 2).<\/p>\n

\"\"<\/p>\n

Infographic 2: The effect of \u03b22-agonists on time to exhaustion, time trial performance and VO\u00ad2max<\/sub> stratified by dose. (If the whiskers cross the dotted line the effect is zero)<\/small><\/p>\n

The effect is dose dependent, what are the other take-home points?<\/strong><\/p>\n