Factors Influencing Excess CO₂ Output During and After Short Duration-Intensive Exercise: Focusing on Skeletal Muscle Characteristics

抄録

The purpose of this study was to investigate the relationship between excess CO₂ output during and after short duration-intensive exercise and skeletal muscle characteristics (i.e., muscle fiber type, muscle capillary density and muscle buffering capacity). Twelve healthy males (age; 22.4±2.9 years, height; 172.3±5.8 cm, weight; 65.0±4.8 kg) performed 30-s maximal cycle ergometer sprinting. Excess CO₂ output during and after exercise was obtained through respiratory gas analysis. Excess CO₂ output per unit of time (ExcessVCO₂) was calculated by subtracting VO₂ from VCO₂ during and after exercise. Muscle biopsy samples were taken from the right vastus lateralis muscle, and then muscle fiber type, muscle capillary density and muscle buffering capacity were measured. ExcessCO₂ calculated as the sum of ExcessVCO₂ from the onset of exercise until 15 min after exercise was not significantly correlated with any muscle fiber types, while it was significantly correlated with capillary-to-fiber ratio (r = 0.791, p < 0.01). A significant negative correlation was also demonstrated between ExcessCO₂-to-La peak ratio and muscle buffering capacity (r = -0.645, p < 0.05). These results suggest that ExcessCO₂ during and after short duration-intensive exercise is affected by the amount of H⁺ buffered by nonbicarbonate system and the amount of H⁺ diffusion from muscle to blood depending on the development of muscle capillaries.