Relationship between Heart Rate Variability vs. Occupational Performance, Physical Activity and Fitness Measures in Structural Firefighters

Abstract

Purpose: Occupational readiness of structural firefighters is critical for safety, health, and job performance. Therefore, the purpose of this study was to determine the relationship between heart rate variability (HRV) and firefighter (FF) occupational performance, fitness characteristics and physical activity measures.  Methods:  Twelve male structural firefighters (Age: 37.3 ± 7.6 yr; Height: 183.2 ± 7.1 cm; Body mass: 90.4 ± 13.7 kg) wore an accelerometer for 19.1 ± 5.8 days to quantify physical activity levels. HRV was assessed daily upon waking with a portable electric cardiogram device for 20.8 ± 4.6 days. HRV indices included SDNN, RMSSD, high frequency (HF) and low frequency (LF) components. FFs also completed a simulated fire ground test (SFGT) as well as a battery of fitness tests including estimated 1-repetition maximum (1-RM) shoulder press, deadlift, bench press, bent-over row, and kettlebell swing, and a submaximal prediction of aerobic capacity. HRV was assessed the day of the SFGT (acute HRV) and averaged over all days (chronic HRV). Results: Acute SDNN values were inversely correlated with SFGT time on 3 individual SFGT tasks (r=-.70 to -.75, p<.05) and the overall SFGT time (r=-.74, p=.016). Chronic HF was correlated with frequency of moderate-to-vigorous physical activity (r=.73, p=.011). Chronic RMSSD and SDNN were also correlated with shoulder press (r=.89, p<.01; and r=.88, p<.01 respectively) and bench press strength (r=.78, p=.008; and r=.76, p=.011 respectively). Conclusions: Acute HRV was correlated with SFGT performance, whereas chronic HRV was associated with physical activity and strength measures. These outcomes indicate that HRV parameters may reflect the physiological status of FFs and the complex interaction between HRV, physical activity and fitness outcomes.