Effect of dietary modifications on lactate threshold and onset of blood lactate accumulation during incremental exercise

Summary

To assess the effect of dietary change on (1) the point at which arterial blood lactate concentration (HLa) increases above the resting value (lactate threshold) and (2) the fixed point corresponding to 4 mM of HLa (onset of blood lactate accumulation; OBLA), five healthy male subjects were put on a mixed diet for 3 days, followed by 4 days of a low carbohydrate diet (a low CHO diet), and then 3 days of a high carbohydrate diet (a high CHO diet). Following each type of diet, the subjects performed a progressive bicycle exercise test, during which concentrations of HLa, pyruvate, FFA, and glucose were analyzed from serial samples of arterial blood, and$\dot V_{O_2 }$ was obtained by the Douglas bag method.

The results of this study are as follows:

• (1) FFA was significantly lower, while pyruvate was significantly higher at rest after a high CHO diet than after a low CHO diet (P<0.05). These differences continued throughout the incremental exercise, which indicates the incremental contribution of CHO to metabolism after a high CHO diet and vice versa.

• (2) There was no significant difference in lactate threshold expressed in$\dot V_{O_2 }$ among the three conditions.

• (3) $\dot V_{O_2 }$ obtained at OBLA was significantly lower after a high CHO diet than after a low CHO diet (P<0.01).

It was concluded that the dietary modifications used in this study had no influence on lactate threshold but did affect the point of OBLA. Therefore, dietary conditions should be considered when OBLA is determined using a fixed 4-mM HLa method.