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 taken for analysis during the effort and the following recovery. Blood concentrations of lactate and ammonia, and plasmatic concentrations of alanine, 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 ascent of blood ammonia and lactate vs load curve. There was a high correlation (P < 0.001) between ammonia and lactate during exercise. At the end of the effort, these two variables had significantly increased in comparison with their values at rest (P < 0.01 for ammonia and P < 0.001 for lactate), but they did not correlate with VO2max. The negative correlation existing between ammonia and VO2max at the beginning of the recovery period may imply that muscle NH3 release is inversely proportional to the subject's sports training level, this relation being less evident when blood lactate vs VO2max correlation was considered. Increase in blood glutamate level was greater in trained subjects (P < 0.05). This finding suggests that ammonia elimination is favoured by physical training. In conclusion, ammonia measurements during exercise provide a valuable information about muscle cell oxidative capacity.