[Effect of high and low altitude exposure on the blood pressure response to physical exercise]

Altitude exposure is known to cause an increase in adrenergic activity, blood pressure (BP) and heart rate (HR) in resting conditions. Much less is known on the effects of the hypoxic environment on the BP and HR response to physical exercise. Five physically trained young normotensive subjects underwent a 1-hour long bicycle ergometric test to exhaustion at sea level and after 24 hours of low (1322 m) and high (3322 m) altitude exposure. HR, BP and Hb oxygen (HbO2) saturation were measured throughout the test and the recovery period. The values obtained at 60, 70, 80, 90 and 100% maximum HR were calculated. Resting BP increased by 17.9/20.9 mmHg at 3322 m (p = 0.062/0.012) and by 10.0/12.8 mmHg at 1322 m (NS). However, the BP difference present at rest gradually flattened throughout effort and at peak exercise similar BP values were obtained during the 3 tests. HbO2 saturation was lower at 3322 m compared to the other 2 settings (91.5% vs 96.7% at sea level; p less than 0.0001) and this difference progressively and remarkably increased throughout the ergometric test. At 3322 m a lower workload was reached (189 +/- 39.4 vs 240 +/- 54.8 W; p less than 0.05). In agreement with previous results these data show that exposure to both high and low altitude causes an increase in resting BP and HR; however, during strenuous exercise maximum BP and HR do not exceed the levels attained at sea level, probably on account of the lower workload that may be reached in the hypoxic environment.