Abstract
To determine the predictability of blood lactate accumulation from excess CO2 output derived from bicarbonate buffering of lactic acid during constant exercise, eight normal active volunteers were studied during three stages of constant exercise on a cycle ergometer. Three work rates consisted of 100% (stage I), 120% (stage II) and 150% (stage III) of each subject's anaerobic threshold (AT), each of which was lasted for 4 min. Excess CO2 output (Ex CO2, ml) at each stage of constant exercise was estimated from the integral of difference between total VCO2.and aerobic VCO2 (from regression line for VCO2 and VO2 at exercise intensities below the AT obtained in incremental exercise test). Ex CO2 Per body mass (Ex CO2·mass-1) was increased progressively with blood lactate (La) accumulation from rest to each stage of constant exercise. Mean values (± SD) in the measured La accumulation (ΔLa, measured) and predicted La accumulation (ΔLa, predicted) at three stages of constant exercise were 1.82 ± 0.83 vs 3.19 ± 1.70 for stage I, 5.58 ± 3.47 vs 7.09 ± 3.28 for stage II and 12.19 ± 2.36 vs 12.74 ± 1.83 mmol·l-1 for stage III, respectively. There was a significant difference between ΔLa, measured and ΔLa, predicted at Stage I (p<0.05), but no significant differences between these two variables at stage II and III. The averaged difference from ΔLa, predicted to ΔLa, measured at stage III (0.55 rrunol·l-1) showed a tendency to be smaller than stage I (1.38 mmol·l-1) and II (1.50 mmol·l-1). On the other hand, ΔLa, predicted was found to correlate very closely with ΔLa, measured (r=0.954, P<0.001, n=20). The results of this study suggest that the changes of La accumulation could be predicted from excess CO2 0utput generated in constant exercises above the AT.
