RELATIONSHIP BETWEEN CO₂ EXCESS DUE TO LACTIC ACID PRODUCTION DURING EXERCISE AND ENDURANCE PERFORMANCE

Abstract

A study was conducted to assess the relationship between CO₂ excess due to lactic acid production during exercise and endurance performance in order to clarify the availability of CO₂ excess as an index of endurance capacity. Four healthy males (control group; CON) aged 21-24 years, and six male long-distance runners (LDR) aged 18-22 years, were subjected to incremental maximal testing on a cycle ergometer and 12-min exhaustive track running. The results obtained are summarized as follows.
1) Mean values (±SD) of CO₂ excess (ml) were 3, 442±677 ml for LDR and 2, 667±437 ml for CON, respectively. On the other hand, the mean value of CO₂ excess per unit body weight (CO₂ excess/w) obtained in LDR (59.1±9.07 ml⋅kg^-1) was significantly higher than that in CON (40.3±3.54 ml⋅kg^-1) (p<0.01) .
2) The ratio of CO² excess/w to ΔLA (the difference between blood lactate at 1 min after exercise and that at rest) showed a tendency to be higher in LDR (5.59±1.16 ml⋅kg^-1⋅mmol^-1) than in CON (4.46±0.69 ml⋅kg^-1⋅mmol^-1) . However, there was no significant difference between these two groups in the ratio of CO² excess/w to ΔLA.
3) The CO² excess/w (ml⋅kg^-1) was significantly related to Vo₂max (r=0.813, p<0.01) and Vo₂AT (r=0.892, p<0.001), respectively. Moreover, CO₂ excess/w was significantly correlated with ΔHCO₃- (the difference between blood bicarbonate at l min after exercise and that at rest) (r=0.649, p<0.05) .
4) The CO₂ excess (ml) and CO₂ excess/w (ml⋅kg^-1) were significantly correlated with 12-min exhaustive running performance (r=0.715, p<0.05, r=0.933, p<0.001), as was the ratio of CO₂ excess/w to d LA (r=0.671, p<0.05) .
5) From these results, it was suggested that the CO₂ excess/w and the ratio of CO₂ excess/w to ΔLA could be important factors related to performance of endurance exercise (i. e., 3, 000-5, 000 m running) accompanied by blood lactate accumulation.