The purpose of this study was to compare heart rate recovery (HRR) after a maximal treadmill (MAX-TM) and three-minute all-out (3MT) test between firefighters (FF) and a control (CON) group. Nine male CON and nine male FF participants completed height (m), weight (kg), body fat percent (BF%), normalized handgrip (GRIP_NORM, kg/kg), and MAX-TM with direct gas analysis to capture aerobic capacity (VO_2PEAK, mL/kg/min). A shuttle-sprint 3MT was used to measure critical velocity (CV, m/s) and D′ (m). Non-linear models determined HR decay (HRR_τ), HR asymptote (HR_∞), and HR amplitude (HR_amp). Two-way GROUP (FF vs. CON) by TEST (MAX-TM vs. 3MT) repeated measures ANOVAs indicated a significant TEST (F = 7.004, p = 0.018) effect on HR_amp. When divided by VO_2PEAK classification (FITNESS), a significant TEST effect was observed (F = 7.661, p = 0.014) on HR_amp. VO_2PEAK was significantly related to CV (r = 0.583, p = 0.011), GRIP_NORM (r = 0.668, p = 0.002), and BF% (r = −0.890, p < 0.001). Complete autonomic nervous system recovery may depend on the intensity of task demands and cardiorespiratory fitness.

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 (VO_2PEAK, mL·kg⁻¹·min⁻¹), average minute ventilation (V_E, L·min⁻¹), and respiratory exchange ratio (RER) in each zone was measured via indirect calorimetry. Linear mixed models determined significant differences in V_E, RER, and time in zone (min). Results: Significant relationships emerged between VO_2PEAK 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 V_E (F = 516.01, p < 0.001) indicating that V_E increased as zone intensity increased. After controlling for VO_2PEAK, 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 VO_2PEAK. 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.

Recruitment of firefighters is, in part, hindered due to attrition from fire academies. This study explored initial fitness differences between those who graduated (GRAD) or were released (REL) from the academy. During the first week of the academy, recruits (N = 407; GRAD = 354, REL = 53; 26.6 ± 7.2 yrs; 177.6 ± 8.6 cm; 87.9 ± 17.2 kg) completed an assessment battery including: body composition using skinfold calipers to estimate percent body fat (BF) and fat-free mass (FFM); shoulder mobility via Apley’s scratch test (APLEY); aerobic fitness (VO_2peak) and heart rate recovery (HRR_1min) estimated from the five-minute Forestry step test; muscular strength via the sum of right and left handgrip (SHG); and muscular endurance via a paced two-minute push-up test (PU). A t-test identified age differences between GRAD and REL, followed by separate ANCOVAs for each fitness measure, and logistic regression to identify the ability of fitness measures to predict academy outcome. GRAD had a lower age and BF and a higher FFM, VO_2peak, SHG, and PU, but did not differ in APLEY or HRR_1min. The full model predicting release was significant; age, BF, and FFM were significant predictors. These results provide pre-fire academy preparation guidance for optimizing the potential for successful academy completion.

This longitudinal study explored entry route- and age-related fitness differences between cadet (CR) and general population (GR) firefighter recruits. Fitness data were collected from eight separate firefighter recruit academy cohorts (N = 317; 122 CR, 195 GR; 27.17 ± 7.58 yrs, 177.30 ± 8.72 cm, 88.65 ± 17.78 kg). In the first week of the academy, recruits completed an assessment battery including: body composition via skinfold measures to estimate body fat (BF, %) and fat-free mass (FFM, kg); aerobic fitness (VO2peak, mL· kg-1· min-1) and heart rate recovery (HRR1min, %) estimated from the five-minute Forestry Step Test; movement quality via a squat-based movement screen (MES, 0-100); muscular strength via the sum of right and left handgrip (SHG, kg); and muscular endurance via a two-minute push-up test. Due to non-normally distributed data, non-parametric statistical tests were used. Wilcoxon rank-sum tests (α < 0.05) evaluated fitness differences between entry routes. Kruskal-Wallis tests evaluated differences between four age groups: A1 (19-21 yrs), A2 (22-29 yrs), A3 (30-39 yrs), and A4 (40+ yrs). CR had significantly (p < 0.05) lower age, BM, BF, and FFM, but greater MES, VO2peak, HRR1min, and PU. A1 had lower BM, BF, and FFM; and greater VO2peak, HRR1min, and PU (p < 0.01) than all other ages. The range of fitness in recruits upon academy entry necessitates careful programming to support optimization of fitness in all recruits, regardless of age. The fitness elements of an academy may present opportunities to build health and fitness literacy, necessary for career longevity.