The Impact of Body Composition and Physical Fitness on Parasympathetic Reactivation in Firefighters

Objective: Firefighting involves aerobic and anaerobic physical activities that cause heart rates to rise from submaximal to above maximal levels. These varying demands can occur with each call firefighters respond to during their shift, imposing both acute and cumulative cardiovascular loads. Heart rate is commonly used to measure cardiovascular responses during disasters, emergencies, firefighting, and firefighting simulations. There is substantial evidence suggesting that heart rate recovery (HRR) parameters are associated with body composition and aerobic fitness. Therefore, the primary aim of this study is to determine the relationship between body composition, physical fitness, and HRR parameters in firefighters. Method: This cross-sectional descriptive study was conducted among firefighters working in a metropolitan municipality. Using the G-Power 3.1 program, seventy-four firefighters (age = 32.61 ± 8.9 years, height = 1.76 ± 0.6 cm, weight = 83.9 ± 13 kg) volunteered to participate in this study. Body mass index (BMI), waist circumference (WC), and body fat percentage (BFP) were recorded for each subject. To determine aerobic fitness (VO2max), each participant performed a submaximal exercise test on a treadmill. HRR was calculated as the difference between peak heart rates post-exercise (HRmax) and heart rates at the first and second minutes of the recovery phase, recorded as HRR1 and HRR2, respectively. Results: The mean VO2max and BMI of the participants were 48.32 ± 9.18 ml/kg/min and 27.10 ± 3.49 kg/m², respectively. No significant relationship was found between the HRR1 and HRR2 parameters and the variables of BMI, WC, and BFP in firefighters (p>0.05). However, positive significant relationships were detected between HRR1 and HRR2 and VO2max (p<0.05). A statistically significant negative relationship was found between VO2max and the variables of BMI, WC, BFP, and weight (p<0.05). These findings indicate that higher aerobic capacity is associated with better heart rate recovery and lower body fat percentage. Conclusion: The results of this study demonstrate that cardiovascular autonomic function is significantly related to maximum aerobic fitness. However, no measure of body composition appears to affect the overall HRR response of the firefighters. This research provides important insights into how the aerobic capacity of firefighters affects their heart rate recovery responses. These findings offer a crucial foundation for improving the physical fitness levels and maintaining the cardiovascular health of firefighters.