Effect of beta(1)-selective adrenergic blockade on maximal blood lactate steady state in healthy men

The aim of this study was to compare the effect of taking bisoprolol (B), a highly beta(1)-selective adrenoceptor antagonist to that of a placebo (P) on maximal lactate steady state (MLSS), which reflects the transition from oxidative to partially anaerobic metabolism. Ten healthy male subjects [mean (SD) age 23 (3) years, height 181 (6) cm, body mass 76 (6) kg] randomly received oral P or B (5 mg x day(-1)) for 2 weeks using a double-blind crossover design. In the 2nd week, the subjects performed an incremental cycle ergometer test until exhaustion to determine the second blood lactate turn point (LTP(2)). At regular intervals of 24-48 h, the subjects performed 2-3 steady-state tests to determine the MLSS. During the incremental exercise, heart rate (HR) was significantly lower at rest (15 beats x min(-1)), at LTP(2) (23 beats x min(-1)) and at maximal power output (19 beats x min(-1)) when taking B compared to P. Oxygen pulse was significantly higher taking B and no significant differences were observed for any of the respiratory gas exchange measurements (RGEM) (oxygen consumption, carbon dioxide production, minute ventilation, respiratory exchange ratio), exercise intensity or blood lactate concentration (LA) at baseline, at LTP(2) and at maximal power output. During exercise at constant intensity, significant differences between B and P were found for HR [148 (12) compared to 176 (11) beats x min(-1)] and oxygen pulse [21.8 (1.9) compared to 19.2 (1.6) ml] at MLSS. No difference was found for exercise intensity [216 (18) compared to 218 (18) W], for RGEM, LA [5.3 (1.1) compared to 4.8 (1.5) mmol x l(-1)] and ratings of perceived exertion [18.1 (1.6) compared to 17.4 (1.7)] for B and P at MLSS. In both, the power output at LTP(2) was slightly higher than power output at MLSS (within an intensity step). Commonly measured cardiorespiratory and subjective variables determined during treatment with 5 mg bisoprolol can be used for testing cardiorespiratory fitness and for prescription of training intensity.