CARDIOVASCULAR-RESPONSE TO EXERCISE AT HI GH-ALTITUDE IN WORKERS CHRONICALLY EXPOSED TO INTERMITTENT HYPOBARIC HYPOXIA

The isottonic work performance was assessed in 34 workers aged 35 +/- 5.8 years old that had working shifts of four days at 4500 m over the sea level and resting periods of other four days at the sea level duri ng at least two years. Subjects were assessed in one occassion at the sea level, and at the first and fourth day of the working shift at 450 0 m over the sea level. Resting arterial oxygen saturation in these th ree periods was 97 +/- 1.1, 88 +/- 18 and 91 +/- 1.1% respectively (p < 0.01), and markedly decreased during maximal and submaximal exercise at 4500 m over the sea level. Exercise duration in the three periods was 931 +/- 210, 775 +/- 105 and 778 +/- 105 seg respectively (p < 0.0 01). Heart rate in the resting period was at least 10% higher and maxi mal and submaximal rates were lower at higher altitude. No differences in blood pressure or packed red cell volume were observed. Exercise d uration correlated inversely with age (r = -0.49 p = 0.03) and directl y with maximal heart rate (r = 0.44 p = 0.009) at the sea level. No co rrelation between aerobic capacity and other measured parameters was o bserved. These results show no differences in the cardiovascular respo nse to exercise between the first and fourth day of stay at high altit ude in workers chronically exposed to intermittent hypobaric hypoxia.