Onset of Blood Lactate Accumulation and Enzyme Activities in M. Vastus Lateralis in Man

Abstract

In an earlier study, we reported close relationships between marathon running performance and the running velocity (V) at which the “onset of blood lactate accumulation” (V_OBLA) occurs in a group of marathon runners. Using biopsy material from the m. vastus lateralis of the same subjects (n = 19), we have evaluated the relationship of V_OBLA to different muscle enzyme activities together with muscle fiber composition and capillary density in the present study. The activities of lactate dehydrogenase (LDH EC 1.1.1.27), phosphofructokinase (PFK EC 2.7.1.11), and citrate synthase (CS EC 4.1.3.7) were determined. V_OBLA was negatively correlated to LDH (r = -0.54) and PFK/CS (r = -0.68). Using multiple regression analysis, the PFK/CS ratio together with the capillary density accounted for 61% of the variation in V_OBLA. Absolute training kilometrage was the most significant variable measured and accounted for 77% of the variation in V_OBLA Subjects were divided into elite runners (n = 6) and nonelite runners (n = 13) for an additional analysis of the relationship between VqblA and the ratios of PFK/CS or LDH/CS. Significant relationships between V_OBLA and the ratios were observed only in the nonelite runners (r = -0.77 and -0.66, respectively). The vertical distances between the regression lines for these two subject groups could not be explained only on the basis of the enzyme activity ratios. A greater adaptation to fat combustion in the elite runners might explain the dis-proportionally high V_OBLA in relation to the PFK/CS or LDH/CS activity ratios.

Key words

blood lactate - muscle fiber type - enzymes - endurance exercise