Study aim: To compare the blood ammonia and lactate concentrations in sprinters and triathletes during an incremental treadmill exercise test and in the 30 minutes of recovery. Material and methods: The study included 10 male sprinters and 14 male triathletes who compete at the national and international level. A treadmill test until exhaustion was administered. Blood samples for ammonia and lactate were obtained when the athletes were at rest, during and immediately after exercise, and between 5 and 30 min after exercise.

Results: The ammonia concentration and time course were similar in the sprinters and triathletes (F = 1.81, p ≥ 0.05, η2 = 0.08). An exercise-related increase in blood ammonia was almost linear, regardless of the exercise intensity. In the case of lactate, the interactions between the concentrations measured in the sprinters and triathletes were statistically significant (F = 5.78, p ≤ 0.001, η2 = 0.21). Post-hoc tests revealed that the lactate concentrations differed significantly between the sprinters and triathletes in the 18th min (p ≤ 0.01) and the 21st min (p ≤ 0.001) of the exercise test. The blood lactate increased in a nonlinear manner (slowly at lower intensities and rapidly at higher intensities). During the 30 min recovery period, both the ammonia and lactate levels decreased linearly. However, in the sprinters, the peak values were maintained in the first stage of recovery (5 min post-exercise).

Conclusions: The study showed that the blood ammonia concentration may be a useful marker of exercise-related metabolic responses in sprint-trained as well as in endurance-trained competitive athletes. Blood ammonia levels were more intensity-sensitive across the whole intensity range during the incremental exercise when compared to the blood lactate levels.