Effect of endurance training on excessive CO₂ expiration due to lactate production in exercise

Summary

We attempted to determine the change in total excess volume of CO₂ Output (CO₂ excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO₂ excess and distance-running performance. Six male endurance runners, aged 19–22 years, were subjects. Maximal oxygen uptake (VO_2max), oxygen uptake (VO₂) at anaerobic threshold (AT), CO₂ excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for C02 excess per unit of body mass per unit of blood lactate accumulation (Ala⁻) in exercise (CO₂ excess·mass⁻¹·Δla⁻), 12-min ERP, VO₂ at AT (AT-VO₂) and VO_2max on average were 0.8 ml·kg⁻¹·l⁻¹·mmol⁻¹, 97.8m, 4.4 ml·kg⁻¹· min⁻¹ and 7.3 ml·kg⁻¹·min⁻¹, respectively. The percentage change in CO₂ excess·mass⁻¹·Δla⁻ (15.7%) was almost same as those of VO_2max (13.7%) and AT-VO₂ (13.2%). It was found to be a high correlation between the absolute amount of change in CO₂ excess·mass⁻¹·Δla⁻ and the absolute amount of change in AT-VO₂ (r=0.94, P<0.01). Furthermore, the absolute amount of change in C02 excess·mass⁻¹·Δla⁻, as well as that in AT-VO₂ (r=0.92, P<0.01), was significantly related to the absolute amount of change in 12-min ERP (r=0.81, P<0.05). It was concluded that a large CO₂ excess·mass⁻¹·Δla⁻¹ of endurance runners could be an important factor for success in performance related to comparatively intense endurance exercise such as 3000–4000 m races.