Blood lactate changes in men during graded workloads at normal atmosphericpressure (100 kPa) and under simulated caisson conditions (400 kPa)

Objectives: A hyperbaric environment may influence lactate metabolism due t o hyperoxia affecting biochemical pathways. The purpose of our study was to determine the blood lactate levels occurring at high workloads in a sample of professional livers under simulated caisson conditions, The ambient air pressure was equivalent to a diving depth of 30 m of seawater (400 kPa). M ethods: A total of 23 healthy male subjects performed graded bicycle exerci se in a dry hyperbaric chamber up to a maximum of 3.5 W kg(-1) body weight at normal (100 kPa) and elevated ambient air pressure (400 kPa). The blood lactate level and the heart rate were measured. Results: In comparison with control conditions, the heart rate and the peripheral blood lactate level were significantly lower at depth for ail workloads. Conclusions: The diffe rences between the normobaric and hyperbaric lactate values may be explaine d by an overall improvement in lactate metabolism at elevated ambient press ure, especially in the working muscles and the organs responsible for the l actate reduction, i.e., the liver. The reduced heart rate may be an effect of the improved tissue oxygen supply at depth.