Although numerous studies have reported the physiological strain associated with firefighting, cardiac responses during a large-scale fire operation have not been reported and cardiac responses have not been compared based on crew assignment. The aims of this study were (1) to characterize cardiac strain during simulated high-rise firefighting, and (2) to compare the cardiac strain associated with different work assignments (fire suppression vs. search and rescue) and different modes of vertical ascent (stairs vs. elevator). Firefighters (N = 42) completed one assignment (fire suppression, search and rescue, or material support) during one of two trials that differed by ascent mode. Assignments were divided into three phases: Ascent (ascend lobby to 8th floor), Staging (remain in holding area on 8th floor), and Work (perform primary responsibilities). When comparing assignments within the same ascent mode, mean heart rate (HRmean) was higher (p = 0.031) for fire suppression than for search and rescue during Work in the stair trial (170 ± 14 vs. 155 ± 11 beats/min). Search and rescue crews experienced greater cumulative cardiac strain (HRmean × duration) during Work than did fire suppression crews (stairs: 1978 ± 366 vs. 1502 ± 190 beats; elevator: 1755 ± 514 vs. 856 ± 232 beats; p<0.05). When comparing ascent mode, HRmean and peak heart rate (HRpeak) were higher (35-57 beats/min; p≤0.001) for both fire suppression and search and rescue during Ascent and Staging phases in the stairs vs. the elevator trial. During Work, HRmean was higher (p = 0.046) for search and rescue in the stairs vs. the elevator trial (155 ± 11 vs. 138 ± 19 beats/min). HRmean and HRpeak were 47 and 34 beats/min higher (p < 0.01), respectively, when materials were transported to the staging area using the stairs compared with the elevator. Study findings suggest that high-rise firefighting results in considerable cardiac strain and that search and rescue and material support crews experienced more cardiac strain than fire suppression crews due primarily to differences in assignment duration. Furthermore, using stairs to transport firefighters and equipment to upper floors results in significantly greater cardiac strain than using the elevator.
Keywords: cardiovascular strain; crew size; firefighter; heart rate; stairs.