The purpose of these experiments was to determine the effects of acute beta-blockade on the kinetics of oxygen uptake (V̇o2), expired carbon dioxide (V̇oo2), and expired ventilation (V̇E) in the transition from rest to submaximal exercise. Six male subjects exercised for 6 min on a cycle ergometer (60 W) initiated as a square wave form rest on two occasions. The beta-blockade experiment began 60 min after the subejct ingested propranolol hydrochloride (1 mg·kg-1 BW) while the second experiment served as control with the treatment order counterbalanced. Ventilation and gas exchange were monitored by open circuit techniques and the data were modeled with a single-component exponential function using a time delay. No differences existed (p > 0.05) in the steady state V̇o2, V̇co2 and V̇E nor the kinetics of V̇E between treatments. However, the rate of adaptation of V̇o2 toward steady state was significantly slowed (p < 0.05) with beta-blockade. These data suggest that acute beta blockade results in diminished V̇o2 kinetics in the transition from rest to steady-state exercise. We hypothesize that the mechanism to explain this finding is a slowed time course of cardiac output adjustment at the beginning of exercise.
|Original language||English (US)|
|Number of pages||4|
|Journal||Aviation Space and Environmental Medicine|
|State||Published - Jan 1 1988|
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health