High-dose inhaled terbutaline increases muscle strength and enhances maximal sprint performance in trained men

Abstract

High-dose inhaled terbutaline elicits a systemic response that enhances muscle strength and sprint performance. High-dose terbutaline should therefore continue to be restricted in competitive sport.

Salbutamol effects on systemic potassium dynamics during and following intense continuous and intermittent exercise

“…When administered by inhalation, the effects of terbutaline during intense exercise were less clear, but appears to reduce post-exercise venous [K + ]. Terbutaline inhalation (3 mg) did not affect incremental treadmill exercise performance, but lowered post-exercise venous [K + ] (~0.2-0.3 mM) (Larsson et al 1997), whilst inhalation (450 µg) enhanced 30 s sprint cycling performance and reduced the post-exercise antecubital venous [K + ] by up to 0.6 mM (Hostrup et al 2014b). However, terbutaline is prohibited by the World Anti-Doping Agency (WADA), whereas salbutamol is permissible for athlete treatment, by inhalation only, up to 1600 µg.d -1 for the purposes of asthma management (WADA 2016).…”

“…Terbutaline was recently shown to protect against an exercise-induced decline in NKA activity (Hostrup et al 2014b) and other β-adrenergic agonists also induced K + -lowering effects during continuous exercise in humans (Hallen et al 1996;Rolett et al 1990); this effect was reversed with β-blockers, resulting in greater elevations in K + Katz et al 1985). However, whilst terbutaline lowered [K + ] a it also enhanced K + loss from contracting muscles due to a greater leg blood flow (Rolett et al 1990), suggesting the K + -lowering effect of β 2 -agonists occurred in non-contracting muscles and/or other tissues.…”

“…Potassium clearance during exercise also occurs via uptake by other non-contracting or relatively inactive muscles, and also splanchnic K + uptake (Lindinger 1995;Sejersted and Sjøgaard 2000;Clausen 2003 (Hostrup et al 2014a;Collomp et al 2000;Grove et al 1995;Newnham et al 1993;Van Baak et al 2000), or in samples drawn only after completion of, rather than during exercise (Hostrup et al 2014a;Kalsen et al 2014;Hostrup et al 2014b;Larsson et al 1997;Grove et al 1995); and/or utilised oral salbutamol (Collomp et al 2000;Van Baak et al 2000;Hostrup et al 2014a;Goubault et al 2001 after prolonged cycling to exhaustion (Van Baak et al 2000), or at 5-10 min recovery after repeated 30 s sprints or repeated bouts of high intensity cycling, although greater reductions were evident at 1 or 2 min after some individual bouts (Hostrup et al 2014a). Similarly, after salbutamol inhalation (800 µg), there was no further change in antecubital venous [K + ] at 2-10 min after exhaustive cycling at 85% VO 2peak (Goubault et al 2001).…”

“…Firstly, interpretation is difficult from studies measuring only antecubital venous [K + ] (Hostrup et al 2014a;Collomp et al 2000;Grove et al 1995;Newnham et al 1993;Van Baak et al 2000), as this can underestimate arterial [K + ] by as much as 2 mM during intense exercise, due to substantial K + clearance by forearm muscles (Lindinger 1995;McKenna et al 1997;Lindinger et al 1995;Kowalchuk et al 1988). Secondly, numerous studies measured [K + ] in blood drawn only after completion of exercise (Hostrup et al 2014a;Kalsen et al 2014;Larsson et al 1997;Grove et al 1995;Hostrup et al 2014b), when plasma [K + ] is falling precipitously (McKenna et al 1997;Sejersted and Sjøgaard 2000). Nonetheless, despite these limitations, there is evidence suggesting salbutamol may affect both K + dynamics and performance under certain conditions.…”

“…Performance during a 30 s cycle sprint was enhanced by oral salbutamol (4-8 mg) (Le Panse et al 2007;Collomp et al 2005;Hostrup et al 2014a), with the post-exercise antecubital (Hostrup et al 2014a (Kalsen et al 2014). Inhalation of the β 2 -agonist albuterol (180 µg) increased peak power during a 15 s cycle sprint (Signorile et al 1992), whilst terbutaline inhalation (450 µg) enhanced 30 s cycle sprint power and reduced post-exercise venous (Hostrup et al 2014b). Investigation of the effects of inhaled salbutamol at a higher dose within WADA approved limits, on arterial [K + ] during and in recovery from intense exercise is warranted.…”