Local and systemic effects on blood lactate concentration during exercise with small and large muscle groups

To evaluate the relationship between lactate release and lac]_art and to investigate the influence of the catecholamines on the lactate release, 14 healthy men age 25±3 (SE) year] were studied by superimposing cycle on forearm exercise, both at 65% of their maximal power reached in respective incremental tests. Handgrip exercise was performed for 30 min at 65% of peak power. In addition, between the tenth and the 22nd minute, cycling with the same intensity was superimposed. The increase in venous lactate concentration (lac]_ven) (rest: 1.3±0.4 mmol·l⁻¹; 3rd min: 3.9±0.8 mmol·l⁻¹) begins with the forearm exercise, whereas arterial lactate concentration (lac]_art) remains almost unchanged. Once cycling has been added to forearm exercise (COMB), lac]_art increases with a concomitant increase in lac]_ven (12th min: lac]_art, 3.2±1.3 mmol·l⁻¹; lac]_ven, 5.7±2.2 mmol·l⁻¹). A correlation between oxygen tension (P_vO₂) and lac]_ven cannot be detected. There is a significant correlation between lac]_art and norepinephrine (NE]) (y=0.25x+1.2; r=0.815; p<0.01) but no correlation between lactate release and epinephrine (EPI]) at moderate intensity. Our main conclusion is that lactate release from exercising muscles at moderate intensities is neither dependent on P_vO₂ nor on EPI] in the blood.