Atrial natriuretic peptide during acute and prolonged exercise in well-trained men.

In this study, cardiac performance and circulating immunoreactive atrial natriuretic peptide (Ir-ANP) were measured during sustained exercise to examine the relationship between cardiac filling, heart rate and circulating ANP. Fifteen well-trained male subjects (mean age = 27.6 +/- 1 years) were studied during two exercise sessions. Initially, graded exercise to maximum was performed to determine maximal oxygen consumption (VO2max). On a separate occasion subjects performed 150 minutes of continuous exercise at 70-74% of the maximal heart rate, with radionuclide angiography performed at rest and every 50 minutes, in conjunction with Ir-ANP, blood pressure and heart rate measurements. During maximal exercise subjects reached a VO2max of 47.9 +/- 2.1 ml/kg/min. Ir-ANP increased from 9.8 +/- 1.1 pg/ml at rest to 45.2 +/- 6.6 pg/ml at maximal exercise. Ir-ANP remained elevated (28.9 +/- 3.4 pg/ml) 3 minutes after exercise (p < 0.05). During prolonged exercise, left ventricular end-diastolic filling decreased significantly between 50 and 150 minutes (p < 0.05), with progressive rise in heart rate observed between 50 (141 +/- 8 beats/minute) and 150 minutes (154 +/- 3 beats/min; p < 0.05). No change in left ventricular end-systolic counts, or arterial blood pressure were observed throughout the exercise period. Ir-ANP was elevated significantly during prolonged exercise, increasing from 9.4 +/- 1.7 at rest, to 19.2 +/- 3.4 after 50 minutes, 17.8 +/- 4.3 pg/ml after 100 minutes of exercise (p < 0.05), and 23.5 +/- 2.1 pg/ml by 150 minutes of exercise. A weak correlation (r = 0.33) was observed between heart rate and Ir-ANP throughout the exercise session.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac responses of young women to conditioning for a 10 kilometer race.

Seven previously sedentary women (mean age, 19 yrs) participated in an 11-week running program (4-5 sessions/week) in preparation for a 10 km race. Training intensity was 80-85% of maximum heart rate reserve. Exercise duration began at 20 minutes/session and was lengthened 5 minutes/session every 2 weeks. A control group consisting of 4 women was also evaluated. Maximal oxygen uptake (VO2max, ml/kg/min) increased 11% in the trained group and decreased 6% in the control group during the study (p less than 0.05). Oxygen uptake, cardiac output (Q), and stroke volume (SV) increased significantly (p less than 0.05) in the trained group during each of 3 levels of steady state cycle ergometer exercise (heart rate targets: 115, 135 and 155 beats/min, respectively). Arteriovenous oxygen difference (a-V02 diff) was not increased significantly after training. Resting left ventricular dimensions and performance evaluated by echocardiography also did not change significantly after training. It was concluded that short-term conditioning in this population results in an increased exercise Q without concomitant increases in left ventricular dimensions or arteriovenous oxygen difference.