Exercise training during long-term beta-blockade treatment in healthy subjects

Abstract

Although it is well accepted that treatment with β-blocking drugs impairs endurance exercise capacity acutely, whether a trained state can be achieved while receiving long-term β-blocker therapy is controversial. The apparent attenuation of training reported in some studies has given rise to the theory that adrenergic stimulation represents a unifying mechanism by which endurance training effects are produced. This theory is supported by studies of long-term β-agonist infusions that show apparent training responses. To assess the role of β-adrenergic stimulation produced by exercise in the development of cardiovascular training effects, 39 healthy men were assigned in a random, double-blind fashion to receive oral propranolol, atenolol or matched placebo. Drug doses were titrated individually to minimize the heart rate response to submaximal exercise (dose ranges: atenolol, 50 to 200 mg/day; propranolol, 160 to 320 mg/day). After beginning chronic drug administration, all subjects participated in an intense, supervised 6-week exercise training program (5 days/week, 45 min/day, at least 75% peak heart rate). Adherence to training was monitored by daily supervision; compliance to the medication regimen was assessed by weekly pill counts, medication diaries and plasma drug assay. Maximal exercise testing was performed before and after training. Peak oxygen consumption increased significantly with training in all 3 groups, whether comparisons were made in the presence or absence of medication. The magnitude of change in oxygen consumption did not differ between groups (F = 0.12, p >0.88). Similarly, peak work rate and duration of work increased in all 3 groups. In the absence of drug treatment, submaximal exercise heart rate decreased with training in all groups. Thus, cardiovascular training effects can be produced in healthy men despite the presence of substantial β 1-selective or nonselective β blockade.