Ammonia threshold and ammonia measurement as potential physiological parameters.

摘要

Exercise induces an increase in the blood ammonia level. A series of studies were conducted to demonstrate the potential of employing ammonia threshold and ammonia measurement for training monitoring. Ammonia data collected from highly trained athletes were also presented to demonstrate the application.;During traditional graded exercise, the change in blood ammonia and blood lactate is parallel. Both ammonia threshold and lactate threshold appear at the same workload. The first part of the study demonstrated that a continuous graded exercise with 4-min steps was able to separate the two thresholds and further studies on ammonia threshold are warranted.;The ammonia threshold was then compared to some commonly used physiological parameters and significant correlations with lactate threshold, ventilation threshold and endurance time were identified. The findings suggest that ammonia threshold is a measure for the ability to sustain submaximal exercise.;The effect of training on ammonia threshold was then studied. An 8-week endurance-training program delayed the appearance of ammonia threshold whereas an 8-week sprint-training program did not modify the ammonia threshold. Being sensitive to training, the use of ammonia threshold for training monitoring becomes increasingly possible.;The diet-and-exercise manipulation that first deplete and then supercompensate the glycogen store also modify the ammonia threshold. The ammonia threshold appeared earlier and the ammonia response during exercise increased under the glycogen-depleted state. Under the glycogen-supercompensated state, both the ammonia response and the appearance of the ammonia threshold do not significantly differ from the control. During graded exercise, lactate response decreases both under glycogen depletion and after endurance training. It is difficult to distinguish the two conditions unless the exercise test is continued until exhaustion. However, the inclusion of ammonia measurement in graded exercise will allow earlier differentiation of the two conditions, since ammonia response reduces after endurance training and increases under glycogen-depletion. As both conditions are common in highly trained athletes, the present findings further demonstrate the applicability of ammonia measurement.;In the second half of the study, ammonia response was studied 'in the field setting'. Firstly, the ammonia threshold of a group of junior cyclists was followed for 1 year. The relatively non-specific training was able to slightly improve the VO2peak but did not modify the ammonia threshold. The ammonia threshold, in this group of participants, was significantly correlated to the endurance time and therefore reconfirms that it is a measure of the ability to sustain submaximal exercise.;Lastly, exercise ammonia levels were obtained from highly trained athletes under three exercise protocols. The data adds to the literature as a reference for future application of blood ammonia in training monitoring. The lack of systematic significant correlation between ammonia and rating of perceived exertion suggests that perceived exertion could not be explained solely by increases in blood ammonia level.;The studies were able to demonstrate the potential application of ammonia threshold and ammonia measurement in training monitoring. The application of blood ammonia measurement in training monitoring should be further developed.