CHANGES IN BLOOD AMMONIA-INDUCED BY A MAXIMUM EFFORT IN TRAINED AND UNTRAINED SUBJECTS

Twelve healthy male volunteers, either trained or untrained, performed a maximal exercise on a cycloergometer. Venous blood samples were tak en for analysis during the effort and the following recovery. Blood co ncentrations of lactate and ammonia, and plasmatic concentrations of a lanine, glutamate and glutamine were measured. At the beginning on the effort, ammonia decreased by 32% (P<0.01) in comparison with its mean level at rest; at 77% and 78% of maximum load there was a steeper asc ent of blood ammonia and lactate vs load curve. There was a high corre lation (P<0.001) between ammonia and lactate during exercise. At the e nd of the effort, these two variables had significantly increased in c omparison with their values at rest (P<0.01 for ammonia and P<0.001 fo r lactate), but they did not correlate with VO(2)max. The negative cor relation existing between ammonia and VO(2)max at the beginning of the recovery period may imply that muscle NH3 release is inversely propor tional to the subject's sports training level, this relation being les s evident when blood lactate vs VO(2)max correlation was considered. I ncrease in blood glutamate level was greater in trained subjects (P<0. 05). This finding suggests that ammonia elimination is favoured by phy sical training.In conclusion, ammonia measurements during exercise pro vide a valuable information about muscle cell oxidative capacity.