Objective: We hypothesized that different body composition and fitness of firefighters would affect immune and inflammatory activity after working in the heat.
Methods: Forty-two firefighters worked in the heat (100 ± 5 °C). Changes in leukocytes, platelets, tumor necrosis factor (TNF-α), and C-reactive protein (CRP) were analyzed based on body composition (DXA) and aerobic fitness (VO2max).
Results: Higher baseline leukocytes were observed for high body fat (P = 0.002) and low lean mass (P = 0.023) resulting in the highest peak values. Additionally, significantly lower values for TNF-α were observed with high lean mass at all time points. Platelets were unaffected by fitness or body composition. Furthermore, body mass index (BMI) and VO2max played no role.
Conclusions: Minimizing body fat and increasing lean mass may reduce immune and inflammatory activity of firefighters in the heat.