Acute hypoxia alters lactate threshold in chronic altitude residents

At an identical workload, blood lactate concentration ([La]) is higher in acute hypoxia (H) versus normoxia (N). However, in altitude-acclimatized individuals, the lactate response to incremental exercise in H and with various VO2max protocols is less clear. Subjects (N = 16) residing at moderate altitude completed VO2max tests on a cycle ergometer in N and H (FIO2 = 0.15) using ramp (R) and step (S) protocols. Gas exchange data were obtained breath-by-breath during exercise. Blood samples were obtained for measurement of blood [La]. One-way ANOVA with repeated measures was used to examine differences between lactate threshold (LT) and blood [La] among the various protocols. LT was significantly higher (p2max) and H (67.2 ? 9.6 %VO2max) versus R (59.7 ? 8.9 %VO2max). At VO2max, blood [La] was higher (p>0.05) in R compared to S and H. At 50 %VO2max, blood [La] was significantly higher (p