[Changes in hemodynamics and catecholamines during single-level exercise at the anaerobic threshold and 120% of the anaerobic threshold in normal subjects].

ABSTRACT

Exercise training usually involves the sustained performance of exercise at a prescribed intensity. The effects of exercise performed at the anaerobic threshold (AT) have been widely studied. The effects of single-level exercise on catecholamines and cardiac function were assessed at the AT, and at 120% of the AT in eight healthy Japanese men (mean age 21.9 +/- 1.8 years). 1) Symptom-limited exercise testing utilized the ramp protocol with a bicycle ergometer (20 watts/min) for measuring AT and peak oxygen uptake (peak VO2). 2) Exercise testing was repeated on another day, following the same protocol, with blood sampled to measure norepinephrine (NE) and epinephrine (E) in the resting control state and at the AT and peak exercise. 3) Single-level exercise testing at the AT and at 120% of AT utilized the bicycle ergometer on yet another day. Blood for measurement of NE and E was drawn at 3 and 7 min after achieving a steady-state condition. In addition, the cardiac index (CI) and stroke index (SI) were measured by the CO2 rebreathing method. (1) Mean AT and peak VO2 were 18.3 +/- 1.3 and 40.2 +/- 3.0 ml/min/g, respectively. (2) NE and E measured during ramp exercise testing increased rapidly when the intensity of exercise exceeded the AT. NE measured after 3 and 7 min at the AT during single-level exercise equalled 94.7% and 94.5% of the NE value measured at the AT of ramp exercise, respectively. NE measured after 3 and 7 min at 120% of the AT during single-level exercise was 124.7% and 144.7% at the AT of ramp exercise, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)