Relationships between strength and endurance parameters and air depletion rates in professional firefighters

Abstract

The aim of this study was to quantify the physical demands of a simulated firefighting circuit and to establish the relationship between job performance and endurance and strength fitness measurements. On four separate days 41 professional firefighters (39 ± 9 yr, 179.6 ± 2.3 cm, 84.4 ± 9.2 kg, BMI 26.1 ± 2.8 kg/m²) performed treadmill testing, fitness testing (strength, balance and flexibility) and a simulated firefighting exercise. The firefighting exercise included ladder climbing (20 m), treadmill walking (200 m), pulling a wire rope hoist (15 times) and crawling an orientation section (50 m). Firefighting performance during the simulated exercise was evaluated by a simple time-strain-air depletion model (TSA) taking the sum of z-transformed parameters of time to finish the exercise, strain in terms of mean heart rate, and air depletion from the breathing apparatus. Multiple regression analysis based on the TSA-model served for the identification of the physiological determinants most relevant for professional firefighting. Three main factors with great influence on firefighting performance were identified (70.1% of total explained variance): VO_2peak, the time firefighter exercised below their individual ventilatory threshold and mean breathing frequency. Based on the identified main factors influencing firefighting performance we recommend a periodic preventive health screening for incumbents to monitor peak VO₂ and individual ventilatory threshold.

Figure 1. Physiological responses during the REPE: Heart rate (HR), peak oxygen uptake absolute (VO_2peak absolute) and relative (VO_2peak relative), minute ventilation (VE), breathing volume (BV) and breathing frequency (BF) during ladder climb, treadmill walk, hoist, orientation section and the overall exercise.

Data are shown as means ± standard deviations (SD). *Significant difference between tasks (P < 0.05).

Figure 2. Individual TSA-Scores of all 41 subjects classified into Outstanding, Above Average, Average, Below Average and Poor.

Figure 3. Relationship between the three main performance predictors and TSA-scores identified by multiple regression: relative VO_2peak (left), time in Zone 1 (middle) and breathing frequency (right).