Blood ammonia and lactate concentrations during endurance exercise of differing intensities

The purpose of this study was to examine the changes of blood ammonia concentration ([NH₃]_b) during endurance exercise of differing intensities on the cycle ergometer and to compare [NH₃]_b to the changes observed in the simultaneously monitored blood lactate acid concentrations ([la^-]_b) measurements. A group of 16 endurance-trained athletes participated in the first part of the study and performed exercise of 30 min duration in a randomized order at intensities of 85%, 95%, 100% and 105% of their individual anaerobic threshold (Th_an,ind; E85-E105) which had been determined beforehand by a cycle exercise test with stepwise increments in intensity. In the second part, 18 average endurance-trained sports students underwent exhausting intensive endurance exercise (IEE) with an intensity of 95% of Th_an,ind. An extensive endurance exercise (EEE) of the same duration at 85% of the Than,ind was carried out 2 days later. The [NH₃]_b increased constantly with increasing duration of all exercise. However, [la^-]_b only increased during exercise with intensities above the Th_an,ind (E105). The increase of [NH₃]_b was higher with higher exercise intensities. At IEE, [NH₃]_b was significantly higher from the 30th min than at EEE, whereas [la^-]_b increased from the 5th min. In conclusion, [la^-]_b responded more sensitively to the intensity of exercise than [NH₃]_b, but it is conceivable that in the future measurements of [NH₃]_b could be used to advise on the duration of endurance training. At present, however, the lack of experience and lack of appropriate values still hinders the systematic use of [NH₃]_b measurements in the physiological monitoring of sports training.