Alteration in the lactate threshold with changes in substrate availability.

The lactate threshold (LT) was studied (N=9) during ergometer cycling under control (C), high blood glucose (G), and high blood free fatty acid (F) conditions. During the G trial blood lactate (HLa) was greater than C at all work loads (P less than 0.05) Adjusted blood HLa values (HLa - pre-exercise value = delta HLa), however, were essentially the same for the C and G trials. Determination of the LT disclosed that there was no difference between the two treatments (C = 53.9 +/- 2.6% VO2 max; G=52.7 +/- 3.1% VO2max). Elevation of blood FFA levels, however, reduced both the HLa and deltaHLa at all work loads from 150-250 W (P less than 0.05) although VO2 was the same as C. In addition, a significant increase in the LT (F = 59.8 +/- 2.6% VO2max) was found for the F treatment. These data suggest that (1) the LT can be altered by substrate availability and (2) that muscle tissue anoxia may not be solely responsible for lactate production during submaximal work.

RCT Entities:   Population Interventions Outcomes