Delayed appearance of blood lactate with reduced frequency breathing during exercise

The purpose of the present study was to investigate the blood lactate (LA-) responses to hypoventilation induced by reduced frequency breathing (RFB) during recovery from exercise. Five male subject performed 16 4 min cycling bouts alternating with 16 min rest periods. Exercise intensities were chosen at power outputs corresponding to 30% VO2max at 2 mMLA-, VO2 at 4 mMLA-, and 90% VO2max in each subject. Breathing frequency was voluntarily controlled starting 10 s before each 3rd min of exercise and maintained throughout the rest of the exercise period. Four different breathing patterns at each exercise intensity were used: normal breathing (NB), breathing every 4 s, breathing every 8 s, and maximal RFB. Except for the NB trials, subjects held their breath at functional residual capacity during each breathing interval. The concentration difference of LA- between the 3rd min sample and the 4th min sample was defined as the lactate change during exercise (delta LA-ex), and that between the 4th min sample and the sample at the 3rd min after the end of the exercise as the lactate change during recovery (delta LA-rec). An ANOVA showed significant (p less than 0.05) differences in breathing procedures only in delta LA-rec. delta LA-rec seemed to increase as compared to NB only at VO2 at 4 mMLA- and 90% VO2max, while delta LA-ex remained unchanged as compared to NB in spite of reduced VA. These results might indicate that RFB inhibited lactate removal from working muscles during exercise.