Effects of endurance training on hyperammonaemia during a 45-min constant exercise intensity

Summary

Eleven laboratory-pretrained subjects (initial$\dot V_{O_{2max} }$=54 ml·kg⁻¹·min⁻¹) took part in a study to evaluate the effect of a short endurance training programme [8–12 sessions, 1 h per session, with an intensity varying from 60% to 90% maximal oxygen consumption$(\dot V_{O_{2max} } )$] on the responses of blood ammonia (b[NH ⁺₄ ]) and lactate (b[la]) concentrations during progressive and constant exercise intensities. After training, during which$\dot V_{O_{2max} }$ did not increase, significant decreases in b[NH ⁺₄ ], b[la] and muscle proton concentration were observed at the end of the 80%$\dot V_{O_{2max} }$ constant exercise intensity, although b[NH ⁺₄ ] and b[la] during progressive exercise were unchanged. On the other hand, no correlations were found between muscle fibre composition and b[NH ⁺₄ ] in any of the exercise procedures. This study demonstrated that a constant exercise intensity was necessary to reveal the effect of training on muscle metabolic changes inducing the decrease in b[NH ⁺₄ ] and b[la]. At a relative power of exercise of 80%$\dot V_{O_{2max} }$, there was no effect of muscle fibre composition on b[NH ⁺₄ ] accumulation.