Choice of selective versus nonselective beta blockers: Implications for exercise training

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Administration of β blockers decreases tachycardia during exercise. In this regard, the effects of cardioselective drugs are similar to those of noncardioselective drugs. Beta blockers with partial agonist activity, however, may produce a lesser decrease in tachycardia during exercise. Cardloselective β blockers have significantly less effect than noncardioselective drugs on isoproterenol-induced tachycardia. This may result from 2 factors: the failure of cardioselective drugs to block a β 2 receptor-mediated vasodilator reflex tachycardia and their failure to block cardiac chronotropic β 2 receptors. Exercise increases plasma catecholamine concentrations and the increases are larger in the presence of ft blockers. Cardloselective β blockers produce larger increases. There is evidence for attenuation of exercise conditioning by β blockers and this effect is probably shared by cardioselective and noncardioselective drugs. Beta blockers produce regulatory increases in β receptor density, and physical training may do the opposite. The interaction between these 2 processes remains to be defined.