Arterial versus venous blood lactate increase in the forearm during incremental bicycle exercise

Summary Eight male subjects were studied during incremental bicycle exercise. From the forearm, arterial and venous blood lactate concentrations were measured every minute until exhaustion. There was a statistically significant difference (P<0.01) in the points at which the arterial and venous blood lactates began to increase above the resting level. The onset of increase of lactate in arterial blood occurred at 1.00±0.07 l·min^–1 inO₂ (mean ± SEM), which corresponded to 37.0±1.5% ofO_2max. Its venous counterpart occurred at 1.50±0.17 l·min^–1 inO₂, 55.0±3.8% ofO_2max. The arterio-venous lactate difference became greater after the onset of increase in arterial blood lactate (anaerobic threshold), presumably as consequence of lactate utilization by the forearm muscles.It was concluded that the onset of blood lactate increase differs according to the sites of blood sampling, which should be considered for the interpretation of anaerobic threshold.