Abstract des Autors

The present study assesses interobserver variability and day-to-day reproducibility of ventilatory threshold T(ven) and lactate threshold T(lac) in healthy young men. The data were obtained before and after acute beta-adrenergic blockade with metoprolol (100 mg/d p.o.). Fifteen healthy young men underwent progressively increased treadmill ergometry tests on two separate days (day 1, 2). Ten out of fifteen subjects participated in a third exercise test under an acute beta-adrenergic blockade (day 3). Interobserver variability of oxygen uptake at T(ven) (8%; +/-0.136 l/min) and T(lac) (5%; +/-0.984 l/min) was small and day-to-day reproducibility of T(ven) (7%; +/-0.131 l/min) and T(lac) (7%; +/-0.133 l/min) high. Under acute beta-adrenergic blockade T(ven) occurred at a significantly lower work load (360+/-117 s) as compared with T(ven) of days 1 and 2 (477+/-153 s; p<0.05). Therefore, a significantly lower oxygen uptake (1.409+/-0.29 l/min) could be observed at T(ven) of day 3 as compared with T(ven) of days 1 and 2 (1.852+/-0.30; p<0.001), and T(lac) of days 1 and 2 (1.724+/-0.22; p<0.001). There was a significant linear correlation between oxygen uptake at T(ven) and T(lac) before beta-adrenergic blockade (r=0.86; p<0.001). This correlation, however, was lost following an acute beta-adrenergic blockade (r=0.56; n.s.). The results of this study suggest that T(ven) is a noninvasive index of functional capacity with high day-to-day reproducibility and low interobserver variability, significantly correlated with exercise-induced lactate accumulation in the blood during incremental exercise tests. The discrepancy of oxygen uptake at T(ven) and T(lac) after acute beta-adrenergic blockade, however, implies that T(ven) and T(lac) are not causally linked. Verf.-Referat