What question did this study set out to answer?

The study aims to evaluate the ventilatory and metabolic demands of firefighters during different heart rate zones.

March 2, 2026Open Access

Comparison of Ventilatory and Metabolic Demands Across Percentage-Based Heart Rate Zones in Firefighters

Key Result

Ventilation and respiratory exchange ratio significantly increase with higher heart rate zones, and higher aerobic capacity correlates with more time in high-intensity zones.

Key Points

The study aims to evaluate the ventilatory and metabolic demands of firefighters during different heart rate zones.
Conducted a maximal treadmill test with 48 male firefighters
Monitored physiological responses using chest strap devices
Assessed measures of aerobic capacity, minute ventilation, and respiratory exchange ratio in defined heart rate zones
Significant correlation between VO2PEAK and average RER in Zone 5
Average VE significantly increased with higher heart rate zones
No significant effect on time spent in zone after controlling for VO2PEAK

Structured PICO

Do percentage-based heart rate zones correspond to distinct ventilatory and metabolic demands in active-duty firefighters?

Population

48 male career active-duty firefighters, mean age 38.17 years.

Intervention

Maximal treadmill test measuring physiological responses across 5 percentage-based heart rate zones (50-100% of age-predicted maximal HR).

Outcome

Aerobic capacity (VO2PEAK), average minute ventilation (VE), and respiratory exchange ratio (RER) in each heart rate zone measured via indirect calorimetry.surrogate

Percentage-based heart rate zones correspond to distinct ventilatory and metabolic responses in firefighters, and higher aerobic capacity is associated with greater time spent working in higher heart rate zones.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

Background: The purpose was to determine the ventilatory and metabolic demands in percentage-based heart rate (HR) zones in active-duty firefighters. Methods: Male career firefighters (n = 48, 38.17 ± 9.02 years, 1.79 ± 0.05 m, 88.27 ± 12.50 kg) completed a maximal treadmill test while wearing chest strap monitors to measure physiological responses corresponding to Zone 1 (50–59%), Zone 2 (60–69%), Zone 3 (70–79%), Zone 4 (80–89%), and Zone 5 (90–100%) based on age-predicted maximal HR. Aerobic capacity (VO2PEAK, mL·kg−1·min−1), average minute ventilation (VE, L·min−1), and respiratory exchange ratio (RER) in each zone was measured via indirect calorimetry. Linear mixed models determined significant differences in VE, RER, and time in zone (min). Results: Significant relationships emerged between VO2PEAK and average RER in Zone 5 (r = −0.33) and time in Zone 3 (r = 0.45), Zone 4 (r = 0.41), and Zone 5 (r = 0.41). A significant HR zone effect emerged in VE (F = 516.01, p < 0.001) indicating that VE increased as zone intensity increased. After controlling for VO2PEAK, a significant HR zone effect emerged in RER (F = 11.90, p < 0.001), indicating that average RER increased as zone intensity increased. No HR zone effect was found for time in zone (F = 1.18 p = 0.332) after controlling for VO2PEAK. Conclusions: A practical cardiovascular workload measure, such as percentage-based HR zones determined from treadmill testing, have distinct ventilatory and metabolic responses. Higher aerobic capacity is related to greater time spent working in higher HR zones.