Brief exercise induces an immediate and a delayed leucocytosis

Area of Science:

• Exercise physiology
• Immunology
• Endocrinology

Background:

• Understanding the transient immune system response to acute physical exertion is crucial for sports science and clinical practice.
• Previous research suggests exercise impacts leukocyte counts, but the hormonal mechanisms behind these changes require further elucidation.

Purpose of the Study:

• To investigate the immediate and delayed haematological responses to different types of brief exercise.
• To explore the hormonal (catecholamines and cortisol) influence on exercise-induced changes in white blood cell counts.

Main Methods:

• Haematological profiles were assessed before, during, and up to 5.5 hours after various 30-minute exercise protocols (squash, swimming, jogging, cycle ergometry).
• Cycle ergometry involved workloads eliciting 48%-84% of maximal oxygen consumption.
• Plasma catecholamine and cortisol levels were measured during and after cycle ergometry.

Main Results:

• All exercise types induced an immediate leucocytosis, characterized by increased neutrophils and lymphocytes, which rapidly resolved post-exercise.
• A delayed neutrophilia, significantly larger than the initial rise, peaked approximately 3 hours after exercise onset.
• Elevated plasma catecholamines correlated with the immediate leucocytosis, while increased cortisol levels were associated with the delayed neutrophilia.

Conclusions:

• Brief exercise triggers a biphasic white blood cell response: an immediate, catecholamine-mediated leucocytosis and a delayed, cortisol-mediated neutrophilia.
• These findings provide insight into the neuroendocrine regulation of immune cell mobilization during and after acute physical stress.
• The study highlights the distinct hormonal pathways influencing immune system dynamics in response to short-term exercise.