Exercise metabolism and beta-blocker therapy. An update

The rationale for the concurrent prescription of beta-blockers and programmes of exercise is that both medication and physical activity can improve the quality of life of patients with cardiovascular disease. Difficulties arise when drugs reduce either the physical ability or the motivation to exercise. This article focuses on the physiological limitations to prolonged aerobic exercise in patients receiving beta-blockers. Possible limiting factors to exercise while taking beta-blockers include reduction in heart rate and cardiac output, local alterations to blood flow, changes to muscle and liver glycogenolysis, and alterations to adipose and intra-muscular lipolysis. The disadvantages and advantages of nonselective and beta 1-selective drugs are discussed, as well as those of drugs that have beta 2-agonist properties. Particular emphasis is placed upon the beta-blocker-induced attenuation of the normal increase in fat oxidation during prolonged exercise. There are physiological advantages, especially for the physically active individual, in prescribing beta 1-selective rather than nonselective drugs in controlled release, rather than conventional release, form. Additionally, there may be further advantages in prescribing drugs which have partial agonist properties at beta 2 receptors.