Abstract

Objective: To evaluate the impact of high intensity ultraendurance (HIU) cycling, using it as a possible way to understand muscle injury kinetics and blood immune cells¡¦ release during high intensity prolonged exercises.

Design: Male amateur triathletes enrolled during a cycling race of the International Bike Championship 800 km cycling relay (~23 h). Each athlete alternately cycled 20-25 minutes until exhaustion and performed a total of approximately 200 km.

Results: Creatine kinase levels in blood reached a 300% rise in a sigmoidal pattern, while lactate dehydrogenase levels increased 30-40% following a hyperbolic pattern. Aspartate aminotransferase and alanine aminotransferase levels increased up to 250% and 140%, respectively. Liver injury markers such as alkaline phosphatase and ƒ×-glutamyltransferase remained stable. Platelets increased 20-30% from pre-exercise, and there was no change in hematocrit during the race. White blood cells rose nearly 200%. Leucocytes rose 210% during the race, with a major component coming from neutrophils, which increased more than 300%. Triacylglycerol levels were decreased at the finish and total cholesterol levels remained unchanged. Urate increased (up to 35%) during the first half of the race, and urea levels increased with a different pattern, increasing 45% in the second half.

Conclusions: Here we showed the blood appearance kinetics of muscle injury markers and some metabolites. We suggest that the increase in these enzymes came primarily from muscle damage instead of liver and that white blood cells are selectively mobilized independently of hemoconcentration.