The effect of a week's beta-adrenoceptor antagonism on daytime heart-rates, subjective responses to exercise, and physical activity in normal subjects.

The effects on heart rate (HR) and physical activity of 1 week's treatment with three different beta-adrenoceptor antagonists (20 mg betaxolol (Lorex); 160 mg propranolol LA; or 100 mg atenolol daily) have been compared with placebo in a double-blind study of 12 normal men. On the fifth day of each treatment a body-borne tape-recorder was worn during waking hours for recording of ECG and footfall signals. Each record was calibrated in terms of the subject's response to laboratory ergometer exercise, and a computer analysis provided objective indices of physical activity. While on beta-adrenoceptor antagonists the subjects perceived standard exercise as significantly harder than on placebo and reported more side-effects (albeit mild and transient). Ambulatory monitoring of HR showed that subjects spent 13% of their waking day at heart rates below 50 beats min-1 while on propranolol, compared with 1% on placebo and 20% on atenolol and betaxolol. On these latter drugs, the group spent as much as 10% of their waking time with HR below 45 beats min-1. The lowest individual heart-rates recorded were below 35 beats min-1. Objective indices of physical activity, such as the duration of periods spent with heart rates above the HR found at 100 W in the ergometer test, showed no differences between the treatments. This negative finding was confirmed by pedometer step counts over the whole week.