Changes of white blood cell count during prolonged exercise.

Area of Science:

• Exercise Physiology
• Immunology
• Sports Medicine

Background:

• Leukocytosis, an increase in white blood cells (WBCs), is typically associated with short- to medium-duration exercise.
• The response of WBC counts during and after prolonged, strenuous physical activity remains less understood.

Purpose of the Study:

• To investigate changes in leukocyte counts during and after prolonged endurance exercise.
• To explore the relationship between WBC counts, exercise duration, and muscle damage markers.

Main Methods:

• White blood cell (WBC) counts were measured in 15 endurance-trained athletes before, during (at 16 and 24 hours), and after a 24-hour, 120 km march.
• Plasma creatine phosphokinase (CPK) activity was assessed as an indicator of muscle damage.
• Data were corroborated with findings from three separate marches (40, 70, and 120 km) involving a second group of subjects.

Main Results:

• WBC counts significantly increased after 16 hours of marching (from 8.5 to 11.3 x 10^9/L) but returned to baseline levels (7.1 x 10^9/L) by 24 hours.
• Plasma CPK activity showed a significant parallel increase after 16 hours (from 127 to 539 U/L), indicating muscle cell damage.
• WBC counts remained near baseline during 64 hours of recovery post-exercise.

Conclusions:

• In extremely long marches, WBC counts may return to pre-exercise levels before the activity concludes.
• The observed decrease in WBC counts during prolonged exercise might be attributed to their infiltration into damaged muscle tissue.
• This suggests a distinct immune response to ultralong endurance events compared to shorter exercise bouts.