A previous study demonstrated a higher proinflammatory response (MCP-1) following an anti-inflammatory response (IL-6) after the treadmill test in heat stress that could contribute to the understanding of the pronounced inflammatory response (leukocytosis) followed by anti-inflammatory response (lymphopenia) induced by the marathon and the lower levels of CRP in HE [36], in spite of half marathon not demonstrating inflammatory or immunological changes in hot and humid environment [41]. Here, IL6 is linked to Increased total leukocyte count.