Call for Advanced Training and Diet Programs Due to High Metabolic Demands of Firefighting

Firefighters (FF) require high levels of muscular strength and cardiovascular fitness in order to meet the demands of firefighting. The National Fire Protection Association reported FF in the US are not meeting health and fitness recommendations, which results in poor simulated and on-duty occupational performance. PURPOSE: to examine the demands and stress placed on FF during a series of simulated FF specific physical tasks and identify potential strategies to improve FF specific performance variables. METHODS: Twenty apparently healthy male professional structural FF completed a battery of nine FF specific exercises/movements during a simulated fire ground test (FGT). The exercise included the following: dry hose carry, charged hose carry, low-room search, chainsaw roof walk, forced entry task, ladder carry, stair climb with hose pack, 10 full extension, and victim carry. A familiarization trial was completed prior to testing. Lactate, time to completion, air tank depletion (measured in PSI) and heart rate were recorded. RESULTS: Lactate levels were significantly higher during post-testing compared to resting levels (p \u3c 0.001). Lactate levels were taken before and two-, four-, six, and eight-minutes after the FGT (1.4 ±0.5 mmol/L, 13.2 ±1.7 mmol/L, 13.3 ±2.2 mmol/L, 12.8 ±1.6 mmol/L, 12.2 ±1.9 mmol/L, respectively). Additionally, heart rate (bpm) at timepoints two and three were significantly higher compared to timepoint one (p \u3c 0.001). Heart rate increased significantly from pre FGT 91.2 ±12.4 bpm to 179.2 ±9.5 bpm during the FGT, which was higher than 95% age-predicted max heart rate. In terms of air tank depletion, the FGT resulted in a significant depletion in tank (p \u3c 0.001). A 45-minute air tank depleted approximately 51% within seven minutes. The average FGT time-to-completion was 7.5-minutes. CONCLUSION: Firefighting requires high levels of physical fitness to carry out the job specific tasks. Standardized resistance training programs and dietary interventions are warranted to identify optimal strategies to improve FF specific performance during simulated testing and on-duty tasks. Tactical resistance programming and diet interventions may reduce the impact of physiological and psychological stressors while improving FF ability to meet metabolic and job-specific demands

Aerobic fitness impacts sympathoadrenal axis responses to concurrent challenges

The combination of mental and physical challenges can elicit exacerbated cardiorespiratory (CR) and catecholamine responses above that of a single challenge alone. Purpose This study examined the effects of a combination of acute mental challenges and physical stress on cardiorespiratory and catecholamine responses. Method Eight below-average fitness (LF VO2max = 36.58 +/- 3.36 ml(-1) kg(-1) min(-1)) and eight above-average fitness (HF VO2max = 51.18 +/- 2.09 ml(-1) kg(-1) min(-1)) participants completed an exercise-alone condition (EAC) session consisting of moderate-intensity cycling at 60% VO2max for 37 min, and a dual-challenge condition (DCC) that included concurrent participation in mental challenges while cycling. Result The DCC resulted in increases in perceived workload, CR, epinephrine, and norepinephrine responses overall. HF participants had greater absolute CR and catecholamine responses compared to LF participants and quicker HR recovery after the dual challenge. Conclusion These findings demonstrate that cardiorespiratory fitness does impact the effect of concurrent stressors on CR and catecholamine responses

Slow Breathing Reduces Markers of Stress in Response to a Virtual-Reality Active Shooter Training Drill

Law enforcement officers are expected to respond to potential life-threatening scenarios in high stress environments. Acute participation in virtual reality (VR) active shooter scenarios has been shown to increase markers of stress. Tactical occupations (i.e., military, law enforcement personnel) are trained to use slow breathing methods to aid in stress reduction, but there is no known evidence supporting the effectiveness of slow breathing in relation to a VR-active shooter training drill (VR-ASD). PURPOSE: To determine the effects of slow breathing on markers of stress in response to a VR-ASD. METHODS: A parallel between subjects design was used, during which, eighty-one (n=81) subjects performed five minutes of either slow breathing method 1 (SB1), slow breathing method 2 (SB2), or no modified breathing [normal breathing (NB)] immediately pre and post VR-ASD. SB1 (i.e., box breathing) involved a four second inhalation, two second pause, four second exhalation, and a two second pause. SB2 involved a four second inhalation, followed by a two second exhalation. The VR-ASD (~1 minute) included a single gunman and simulated victims. Subjects were fitted with a VR headset and equipped with a Glock 17 training pistol. Salivary samples and heart rate (HR) were collected thirty minutes pre, five minutes pre, five minutes post, and thirty minutes post VR-ASD. Saliva was analyzed for stress markers: α-amylase (AA) and secretory immunoglobulin-A (Sig-A). AA and SIgA were analyzed via 3x4 (treatment x timepoint) factorial ANOVAs. HR was analyzed via 2x4 factorial ANOVA. RESULTS: Both methods of slow breathing (SB1 and SB2) resulted in significantly lower AA concentrations at five (p \u3c 0.001), and thirty-minutes post VR-ASD (SB1: p= 0.008; SB2: p \u3c 0.001) compared to NB. In the NB condition, AA concentrations were significantly elevated five minutes post VR-ASD (p \u3c 0.001) compared to all other timepoints but did not change across time in SB1 or SB2 (p \u3e .05). A significant increase in SIgA concentrations was noted five minutes post VR-ASD compared to all the other time points (p \u3c 0.001), and significantly higher SIgA concentrations were found in the NB compared to SB1 and SB2 (p\u3c0.001). Finally, slow breathing resulted in a significant decrease in HR from pre to post VR-ASD (p \u3c 0.05). CONCLUSION: The VR-ASD resulted in a significant increase in stress markers AA and SIgA. Slow breathing (both SB1 and SB2) prevented a significant increase in AA concentrations and resulted in lower concentrations post VR-ASD. Future studies should investigate the effects of longitudinal participation in slow breathing methods on markers of stress in response to a VR-ASD

Astaxanthin Reduces Heart Rate and Carbohydrate Oxidation Rates During Exercise in Overweight Individuals

International Journal of Exercise Science 16(2): 252-266, 2023. Astaxanthin (AX) is an antioxidant which may spare endogenous carbohydrates and improve fat oxidation rates, thus improving metabolic flexibility. To date, no studies have attempted to examine the impact of AX in an overweight cohort, whom often suffer from metabolic inflexibility. Nineteen subjects (mean ± SD: age: 27.5 ± 6.3 years; height: 169.7 ± 9.0 cm; body mass: 96.4 ± 17.9 kg; BF%: 37.9 ± 7.0%; BMI: 33.4 ± 5.6 kg/m2; VO2peak: 25.9 ± 6.7 ml·kg−1·min−1) were recruited and supplemented with either 12 mg of AX or placebo (PLA) for 4 weeks. Subjects completed a graded exercise test on a cycling ergometer to examine changes in substrate oxidation rates. A total of 5 stages, each lasting 5 min and resistance increased 15 W each stage, were completed to examine changes in levels of glucose and lactate, fat and carbohydrate (CHO) oxidation rates, heart rate, and rating of perceived exertion (RPE). Although there were no changes found in rates of fat oxidation, blood lactate or glucose, or RPE (all p \u3e 0.05), a significant decrease was observed in CHO oxidation from pre to post supplementation in the AX group only. Further, the AX group demonstrated a 7% decrease in heart rate across the graded exercise test. These findings suggest that 4 weeks of AX supplementation may offer some cardiometabolic benefits to overweight individuals, and be a favorable supplement for these individuals beginning an exercise program

Predictors of Cardiometabolic Disease Risk Factors in Professional Firefighters

The leading cause of mortality (~50% of deaths) among on-duty firefighters is sudden cardiac death. Firefighters with adequate cardiorespiratory fitness levels (among other muscular fitness metrics) and lower body fat percentage (BF%) are likely to better combat on-duty cardiac events and cardiovascular disease (CVD) risk. Individuals with higher VO2max values may be at lower risk noted by lower oxidative stress and inflammatory biomarkers, which may be more ideal predictors of CVD risk compared to traditional biomarkers (i.e., blood glucose and lipids) among the fire community; however, more research is needed to elucidate. PURPOSE: This study examined the relationship between fitness metrics, body fat percentage, and traditional and non-traditional biomarkers among professional firefighters. METHODS: Ninety-eight professional, male firefighters (age = 36.26 ± 9.08 yrs; height = 179.53 ± 7.06 cm; waist circumference = 37.99 ± 4.13 cm; BF% = 24.39 ± 5.21; years of experience = 11.81 ± 8.00 yrs) from a local fire department were studied VO2max was estimated from total treadmill exercise time using the Foster equation.. Fitness metrics including muscular strength, endurance, and power variables were also measured. Fasted blood samples were analyzed for concentrations of lipids, glucose, insulin resistance (HOMA-IR), advanced oxidation protein products (AOPP), and ultra-sensitive C-reactive protein (CRP). To assess the relationship between fitness metrics and AOPP, CRP, and HOMA-IR, ordinary least square regression analyses were used. RESULTS: VO2max values were inversely (p \u3c 0.05) related to AOPP, HOMA-IR, and CRP. Waist circumference was positively correlated to AOPP concentrations and HOMA-IR, while increased BF% was significantly related to increased CRP concentrations. CONCLUSION: High VO2max values were significantly related to lower AOPP, CRP, and HOMA-IR. Additionally, high waist circumference and BF% values were related to increases in oxidative stress, inflammation, and insulin resistance. Firefighters are encouraged to maintain high cardiorespiratory fitness (VO2max) and lower BF% to reduce CVD and, ultimately, on-duty sudden cardiac death risk

Physiological Stress Responses to a Live-Fire Training Evolution in Career Firefighters

Firefighters have a physically demanding job that exposes them to many specific and unique stressors, which contribute to cardiovascular disease (CVD) risk (i.e., cardiovascular strain, inflammation, and oxidative stress) or even mortality. At present, the literature lacks data evaluating these physiological stress responses amongst firefighters in any realistic or simulated scenarios, such as a live-fire training evolution (LFTE). Given the elevated risk of premature mortality, there is a critical need to better understand the physiological stress responses to an LFTE. This information could aid in developing nutritional, training, and other various interventions to mitigate stress load and reduce the incidence of CVD among this population. PURPOSE: To assess the physiological stress response to an LFTE among firefighters. METHODS: Seventy-six (n = 76) career firefighters completed an LFTE. Salivary samples were collected pre, immediately post, and 30-min post the LFTE, and analyzed the following stress markers: α-amylase (AA), secretory immunoglobulin-A (SIgA), and cortisol. One-way repeated measures analysis of variance was used to assess changes over time. Fisher’s LSD and Cohen’s d effect size calculations were used for Post hoc analysis. RESULTS: Significant main effects for time were found for AA, SIgA, and cortisol (p\u3c0.001). Fisher’s LSD post hoc analysis found AA, SIgA, and cortisol concentrations were all significantly elevated immediately post LFTE compared to pre (p\u3c0.0001) and 30-min post (p\u3c0.0001). Medium to large effect sizes were noted for AA, SIgA, and cortisol with respect to changes pre to immediately post-LFTE (d = 0.84, 0.61, and 0.78, respectively). CONCLUSION: While many studies have shown increased inflammation and oxidative stress, as well as adverse cardiovascular and metabolic responses to firefighting activities, these data provide insight into the physiological stress placed upon a firefighter engaging in fire-suppressive evolutions