Effect of β1-selective adrenergic blockade on maximal blood lactate steady state in healthy men

Abstract

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.

Methodological approach to the first and second lactate threshold in incremental cardiopulmonary exercise testing

“…During steady-state exercise, this leads to an equilibrium in BL appearance and BL elimination. The highest workload, which can be performed for about 30 min without a systematic increase in the BL concentration, is called 'maximal lactate steady state' (MLSS) and reflects the gold standard for the determination of the second or 'anaerobic threshold' [6,38,39].…”

“…Three-line regression concepts have incorporated the two LTs into one graph [11]. The 'second lactate turn point' was shown to correlate well with MLSS [38,39] and approximates a BL level of 4 mmol/l [29,15]. The important point in favor of this threshold fixation, however, seems the convenience of a whole number.…”

Special Needs to Prescribe Exercise Intensity for Scientific Studies

“…These authors showed that despite minimal heart rate differences of only 5 b·min −1 between two rowing exercise bouts just below or above VT 2 , growth hormone response was almost doubled in exercise above the VT 2 . Given these findings, the second turn point for La, HR, or VE [29, 30, 65, 71, 76], consistent with the maximal lactate steady state [67, 76], seems to be a criterion for the upper level of exercise prescription in healthy subjects and patients.…”

Nicht-invasive Messung hämodynamischer Parameter bei Patienten mit pulmonal arterieller Hypertonie unter Belastung

“…Normwerte liegen unter Ruhebedingungen im Bereich von 4-6ml/Schlag und steigen unter maximaler Belastung auf etwa 10-20ml/Schlag an (Wonisch 2003 (Smith, Johnson et al 1993). Die Einnahme von Betablockern bei bestehender Herzinsuffizienz führt, bedingt durch die reduzierte Herzfrequenz, zu höheren Absolutwerten des Sauerstoffpulses auf der jeweiligen Belastungsstufe (Wonisch, Hofmann et al 2002).…”