Blood lactate during leg exercise in microgravity

Venous blood lactate concentration ([La]b) was measured in five male subjects (age: 30-50 years; BW: 72-84 kg, VO2max:2.2-3.6 l min-1) during cycloergometric exercise in microgravity obtained by parabolic flight maneuvers of approximately 25 s duration. The subject(s) exercised at 30, 60, 90 and 120 W (60 RPM) for at least 7 min at each intensity. Three consecutive parabolas with approximately 3 min interval were performed at each workload. [La]b was determined at rest and immediately after 60, 90 and 120 W exercise. The day after the flight experiments, the subject(s) underwent the same experimental protocol on the ground and the blood samples were taken at the very same time intervals as on the aircraft. [La]b in flight and control didn't show any appreciable difference once the values are plotted as a function of the relative exercise intensities expressed as a percent of the individual VO2max corrected for the moderate hypoxia prevailing inside the aircraft (cabin barometric pressure = 590 mmHg).