Evaluation of Circuit Training Workout Intensity for Firefighters

Abstract

Firefighters are required to perform a variety of strenuous occupational tasks at the fire ground. Research suggests that these fire ground tasks produce heart rate values of approximately 79-88% of maximum heart rate (HR_max) and peak blood lactate values of 6–13 mMol. Thus, it is critical that firefighters train at an appropriate intensity to develop optimal levels of physical fitness to optimize the performance of these tasks. PURPOSE: To evaluate the objective and subjective intensity of a circuit-based strength and conditioning workout designed for firefighters. METHODS: Twenty career firefighters (mean ± SD; Height: 1.79 ± .05 m; Body mass: 95.4 ± 17.6 kg; BMI: 29.5 ± 4.7 kg/m²) participated in this study. The workout was composed of a circuit that included 8 externally resisted multi-joint exercises and 4 body weight exercises that stressed all major muscle groups and core musculature. Each participant utilized a self-selected load that allowed for 12 repetitions for the externally resisted exercises. The participants were allowed 30 seconds to perform each exercise and 30 seconds of rest before beginning the next exercise. One 3 min bout on a stair climber or treadmill was included in the circuit. Two rotations of the circuit were performed. Heart rate was evaluated using a heart rate monitor and was recorded at the completion of each exercise. The participants rated their perceived exertion (RPE) using a 0–10 category-ratio scale after each exercise and at the completion of the workout (i.e., global RPE). Blood lactate was measured before the workout while at rest and approximately 5 min after the completion of the workout. RESULTS: The participants' mean heart rate increased significantly from 80.3 ± 6.5% of HR_max during the first rotation of the circuit to 86.1 ± 6.0% of HR_max during the second rotation of the circuit (P < .001). The mean RPE of the individual exercises during the first rotation of the circuit increased significantly from 5.3 ± 1.5 (“Hard”) to 6.5 ± 1.5 (“Hard”-“Very hard”) during the second rotation of the circuit (P < .001). The global RPE was 7.3 ± 1.2 (“Very hard”). Pre-workout resting blood lactate was 1.5 ± 0.8 mMol, whereas post-exercise blood lactate increased to 11.8 ± 3.0 mMol (P < .001). CONCLUSIONS: These data indicate that a circuit-based strength and conditioning workout yields similar heart rate and blood lactate values compared to performing tasks on the fire ground. PRACTICAL APPLICATIONS: Firefighters are encouraged to maintain optimum levels of physical fitness to perform occupational tasks. Utilizing a circuit-based workout may be appropriate for firefighters working out on duty because it allows multiple firefighters to workout simultaneously, requires little equipment, and can be performed in a short period of time, while sufficiently stressing energy systems that are utilized on the fire ground. In addition, the 0-10 RPE scale provides a practical way to subjectively set exercise intensity without performing a 1 repetition maximum test. ACKNOWLEDGMENT: This investigation was supported by the Kentucky Fire Commission.