We hypothesized that the cardioselective β1-adrenoreceptor antagonist esmolol would
improve maximal apnea duration in elite breath-hold divers. In elite national-level divers (n=
9), maximal apneas were performed in a randomized and counterbalanced order while
receiving either iv esmolol (150 μg· kg− 1· min− 1) or volume-matched saline (placebo).
During apnea, heart rate (ECG), beat-by-beat blood pressure, stroke volume (SV), cardiac
output (CO), and total peripheral resistance (TPR) were measured (finger …

… placebo-controlled study of its kind, we determined the effects of β1-blockade on
maximal apnea 114 … The primary findings of this study are: 1) β1-blockade with esmolol
improves maximal 335 apnea duration in elite breath hold divers by ~10%, 2) esmolol
reduces MVO2 at each time point 336 …