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

OBJECTIVE: This study assessed firefighters' physiological stress response to a live fire training evolution (LFTE). METHODS: Seventy-six ( n = 76) firefighters completed an LFTE. Salivary samples were collected pre-, immediately post, and 30-min post-LFTE and analyzed for α-amylase (AA), cortisol (CORT), and secretory immunoglobulin-A (SIgA). RESULTS: Concentrations of AA, CORT, and SIgA were elevated immediately post LFTE versus pre (P<0.001) and 30-min post (P<0.001). Cohen's d effect size comparing pre and immediately-post means were 0.83, 0.77, and 0.61 for AA, CORT, and SIgA and were 0.54, 0.44, and 0.69 for AA, CORT, and SIgA, comparing immediately-post and 30-min post, respectively. CONCLUSIONS: These data demonstrate the stress response and activation of the hypothalamic-pituitary-adrenal/sympathetic-adreno-medullar axis and immune system immediately after real-world firefighting operations. Future work is needed to understand the impact of elevated stress biomarkers on firefighter performance and disease risk.

Stress response to virtual reality based active shooter training: Impact of caffeine consumption.

Participation in a virtual reality based active shooter training drill (VR-ASD) has been shown to increase biomarkers of stress; however, the impact of caffeine consumption on this response has not been studied. Caffeine ingestion has been shown to have favorable effects on physical and cognitive performance among athletic and tactical occupations alike. This study examined the impact of caffeine ingestion on subjective and physiological markers of stress in response to a mental stress task (MST) which involved participation in a VR-ASD and cognitive challenge consisting of mental arithmetic and a Stroop challenge. Fifty-three subjects were randomly assigned either caffeine (n = 26) or placebo (n = 27) prior to being exposed to the MST. Saliva samples, heart rate (HR), and state-anxiety inventory (SAI) scales, were collected before and after exposure to the MST. Saliva was analyzed for α-amylase (sAA), secretory IgA (SIgA), and cortisol (sCORT) concentrations. The MST resulted in significant increases in sAA, SIgA, HR, and SAI. Immediately post MST, sAA concentrations were significantly higher following the caffeine treatment compared to placebo. These data demonstrate that caffeine consumption results in significantly greater sAA concentrations post MST. This study was pre-registered as a clinical trial ("Impact of supplements on stress markers": NCT05592561).

Slow Breathing Reduces Biomarkers of Stress in Response to a Virtual Reality Active Shooter Training Drill.

Tactical occupations regularly encounter life-threatening situations while on duty. Although these occupations are often trained to utilize slow breathing (SB) during intense stress, there is no evidence supporting the effects on markers of stress in response to a virtual reality active shooter training drill (VR-ASD). The purpose of the study was to determine the impact of acute SB on biomarkers of stress in response to a VR-ASD. Seventy-nine (n = 79) subjects performed either slow breathing method 1 (SB1), slow breathing method 2 (SB2), or normal breathing (control) for five minutes, both pre- and post-VR-ASD. Saliva samples were analyzed for stress markers, including α-amylase (sAA) and secretory immunoglobulin-A (SIgA). Both methods of SB resulted in significantly lower sAA concentrations at 5 (p < 0.001) and 30 min post-VR-ASD (SB1: p = 0.008; SB2: p < 0.001) compared to the control. In the control condition, the sAA concentrations were significantly elevated 5 min post-VR-ASD (p < 0.001) but did not change across time in SB1 or SB2 (p > 0.05). Thus, both SB1 and SB2 reduced the sAA response and resulted in lower concentrations post-VR-ASD. This study was pre-registered as a clinical trial ("Impact of Breathing Interventions on Stress Markers"; NCT05825846).

A self-selected 16:8 time-restricted eating quasi-experimental intervention improves various markers of cardiovascular health in middle-age male cyclists.

OBJECTIVES: Time-restricted eating (TRE) is a dietary intervention that may offer some protection against cardiovascular disease (CVD), while also preserving performance in athletes. To date however, research on TRE in an active population has only been conducted in college-age cohorts and the effects of TRE in an older, trained population are less understood. Therefore, the aim of this study was to compare the effects of a 4-wk, 16:8 TRE intervention on markers of CVD risk in middle-age, male cyclists. METHODS: Participants (N = 12; age, 51.9 ± 8.6 y; training duration/wk, 375 ± 140 min; peak aerobic capacity, 41.8 ± 5.6 mL/kg/min) reported to the laboratory for two sessions (i.e., at baseline and post-TRE) where blood was drawn from an antecubital vein after an 8-h overnight fast. Dependent variables measured at baseline and post-TRE included insulin, cortisol, brain-derived neurotropic factor, free testosterone, thyroxine, triiodothyronine, C-reactive protein, advanced oxidative protein products, glutathione, tumor necrosis factor (TNF)-α, glucose, and a full lipid profile. RESULTS: Compared with baseline, TRE significantly lowered TNF-α (12.3 ± 3.4 versus 9.2 ± 2.4 pg/mL; P = 0.02) and glucose concentrations (93.4 ± 9.7 versus 87.5 ± 7.9 mg/dL; P = 0.01), as well as significantly elevated high-density lipoprotein cholesterol levels (45.7 ± 13.7 versus 49.2 ± 12.3 mg/dL; P = 0.04), respectively. No further significant changes were observed between the remaining variables (all P > 0.05). CONCLUSION: Overall, these data suggest that incorporating a 4-wk TRE intervention with habitual endurance training can significantly improve some markers of CVD risk and may compliment the robust health benefits derived from a regular exercise regimen.

The Metabolic and Physiological Demands of a Simulated Fire Ground Test Versus a Live-Fire Training Evolution in Professional Firefighters.

Objective: This study examined the similarities in metabolic and physiological demands of a fire ground test (FGT) and a live fire training evolution. Methods: Twenty-seven firefighters completed either a FGT (n = 13) or a live fire training evolution (n = 14). Salivary samples were collected pre, immediately post, and 30-minutes post FGT and live fire training evolution, and analyzed for cortisol, uric acid, and interleukin-1ß (IL-1ß). Heart rate (HR) was measured pre- and post-task. Results: Both tasks resulted in significant elevations in cortisol, IL-1ß, and HR. Conclusions: Both the FGT and live fire training evolution appear to result in similar metabolic and physiological demands. Further work may expand upon the additional elements (i.e., added heat) of the live fire training evolution. Fire departments may consider incorporating a variety of high intensity training to prepare personnel for these occupational demands.

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

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 > 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.

Astaxanthin Supplementation Does Not Affect Markers of Muscle Damage or Inflammation After an Exercise-Induced Muscle Damage Protocol in Resistance-Trained Males.

ABSTRACT: Waldman, HS, Bryant, AR, Parten, AL, Grozier, CD, and McAllister, MJ. Astaxanthin supplementation does not affect markers of muscle damage or inflammation after an exercise-induced muscle damage protocol in resistance-trained males. J Strength Cond Res 37(7): e413-e421, 2023-It is well documented that exercise-induced muscle damage (EIMD) decreases exercise performance by elevated inflammation and subjective discomfort. Due to its potent antioxidative properties, astaxanthin (AX) may serve as a potential dietary supplement strategy for mitigating delayed-onset muscle soreness (DOMS) and enhancing recovery and performance. This study aimed to investigate the effects of AX on markers of muscle damage, inflammation, DOMS, and anaerobic performance and substrate metabolism. Thirteen resistance-trained men (mean ± SD , age, 23.4 ± 2.1 years) completed a double-blind, counterbalanced, and crossover design with a 1-week washout period between 2, 4-week supplementation periods at 12 mg·d -1 of AX or placebo. After each supplementation period, subjects completed 2 trials, with trial 1 including a graded exercise test (GXT) and a 30-second Wingate and trial 2 including an EIMD protocol followed by the collection of fasting blood samples (pre-post) to measure creatine kinase, advanced oxidative protein products, C-reactive protein, interleukin-6, insulin, and cortisol. Astaxanthin supplementation had no statistical effects on markers of substrate metabolism during the GXT, Wingate variables, or markers of muscle damage, inflammation, or DOMS when compared with placebo (all p > 0.05). However, 4 weeks of AX supplementation did significantly lower oxygen consumption during the final stage of the GXT (12%, p = 0.02), as well as lowered systolic blood pressure (∼7%, p = 0.04), and significantly lowered baseline insulin values (∼24%, p = 0.05) when compared with placebo. Collectively, these data suggest that 4 weeks of AX supplementation at 12 mg·d -1 did not affect markers of muscle damage, inflammation, or DOMS after an EIMD protocol in a resistance-trained male cohort.

Effects of Betaine Supplementation on Markers of Metabolic Flexibility, Body Composition, and Anaerobic Performance in Active College-Age Females.

Betaine (BET) has shown to be effective in improving body composition and performance, although research in women is lacking. This study investigated the effects of BET supplementation on markers of metabolic flexibility, body composition, and anaerobic performance in college females. Twenty-three active subjects with 21.8 ± 3.0 years of age, 66.6 ± 8.8 kg body mass, 1.6 ± 0.1 m height, and 23.2 ± 5.3% body fat performed a graded exercise test on a cycle ergometer consisting of 4 incremental, 3 min stages for collection of fat and carbohydrate oxidation rates. Three 10 s sprint tests were then completed against a resistance of 7.5% of body mass, separated by 2.5 min of recovery. The study comprised 3 phases: (a) pre-supplementation, (b) randomization to supplement for 2-weeks with either 2.4 g/day BET or placebo (parallel design), and (c) post-supplementation. Repeated-measures analysis of variance were conducted to determine interactions or main effects. There were no group differences for substrate oxidation rates (p > 0.05). Although body composition improved pre-post for both groups (p < 0.05), only the BET group experienced a significant increase in fat free mass (p < 0.01; ∼3%). Further, only the BET group experienced improvements to performance such as a higher mean power output during the final sprint (p = 0.02; ∼3%) and a lower RPE during the final stage of the graded exercise test (p = 0.02). Results from this study suggest BET supplementation may improve body composition and some markers of performance during exercise in collegiate women.

Device-guided slow breathing alters postprandial oxidative stress in young adult males: A randomized sham-controlled crossover trial.

BACKGROUND AND AIMS: Slow, deep breathing (SDB) lowers blood pressure (BP) though the underlying mechanisms are unknown. Redox improvements could facilitate hemodynamic adjustments with SDB though this has not been investigated. The purpose of this randomized, sham-controlled trial was to examine the acute effects of SDB on oxidative stress and endothelial function during a physiological perturbation (high-fat meal) known to induce oxidative stress. METHODS AND RESULTS: Seventeen males (ages 18-35 years) were enrolled, and anthropometric measurements and 7-day physical activity monitoring were completed. Testing sessions consisted of 24-h diet recalls (ASA24), blood sample collection for superoxide dismutase (SOD) and thiobarbituric acid reactive substances (TBARS) analysis, and flow-mediated dilation (FMD). High-fat meals were ingested and 2-min breathing exercises (SDB or sham control breathing) were completed every 15 min during the 4-h postprandial phase. Blood sample collection and FMD were repeated 1-, 2-, and 4-h post meal consumption. Mean body mass index and step counts were 25.6 ± 4.3 kg/m2 and 8165 ± 4405 steps per day, respectively. Systolic and diastolic BP and nutrient intake 24 h prior were similar between conditions. No time or time by condition interaction effects were observed for FMD. The total area under the curve (AUC) for SOD was significantly lower during SDB compared to the sham breathing condition (p < 0.01). No differences were observed in TBARS AUC (p = 0.538). CONCLUSIONS: Findings from the current investigation suggest that SDB alters postprandial redox in the absence of changes in endothelial function in young, healthy males. CLINICAL TRIAL REGISTRATION NUMBER: NCT04864184. CLINICAL TRIALS IDENTIFIER: NCT04864184.

Risk Factors for Cardiometabolic Disease in Professional Firefighters.

OBJECTIVE: Firefighters are plagued with cardiometabolic disease (CMD). Obesity, poor cardiorespiratory and muscular fitness, and blood lipids (low-density lipoprotein cholesterol, triglycerides, low high-density lipoprotein cholesterol) are risk factors for CMD. However, markers of oxidative stress, inflammation, and insulin resistance can provide further insight regarding CMD risk. METHODS: This study investigated the relationships between fitness metrics (cardiorespiratory and muscular fitness, percent body fat, waist circumference), blood lipids, blood pressure, and years of experience as a firefighter to blood markers of insulin resistance: Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), oxidative stress: advanced oxidation protein products (AOPPs), and inflammation: C-reactive protein. RESULTS: Waist circumference and blood concentrations of triglycerides were significantly related to AOPPs and HOMA-IR. Cardiorespiratory fitness was inversely related to AOPPs, HOMA-IR and C-reactive protein. CONCLUSION: These findings demonstrate the importance of high cardiorespiratory fitness and low waist circumference to reduce markers of CMD.

International society of sports nutrition position stand: tactical athlete nutrition.

This position stand aims to provide an evidence-based summary of the energy and nutritional demands of tactical athletes to promote optimal health and performance while keeping in mind the unique challenges faced due to work schedules, job demands, and austere environments. After a critical analysis of the literature, the following nutritional guidelines represent the position of the International Society of Sports Nutrition (ISSN). General Recommendations: Nutritional considerations should include the provision and timing of adequate calories, macronutrients, and fluid to meet daily needs as well as strategic nutritional supplementation to improve physical, cognitive, and occupational performance outcomes; reduce risk of injury, obesity, and cardiometabolic disease; reduce the potential for a fatal mistake; and promote occupational readiness. Military Recommendations: Energy demands should be met by utilizing the Military Dietary Reference Intakes (MDRIs) established and codified in Army Regulation 40-25. Although research is somewhat limited, military personnel may also benefit from caffeine, creatine monohydrate, essential amino acids, protein, omega-3-fatty acids, beta-alanine, and L-tyrosine supplementation, especially during high-stress conditions. First Responder Recommendations: Specific energy needs are unknown and may vary depending on occupation-specific tasks. It is likely the general caloric intake and macronutrient guidelines for recreational athletes or the Acceptable Macronutrient Distribution Ranges for the general healthy adult population may benefit first responders. Strategies such as implementing wellness policies, setting up supportive food environments, encouraging healthier food systems, and using community resources to offer evidence-based nutrition classes are inexpensive and potentially meaningful ways to improve physical activity and diet habits. The following provides a more detailed overview of the literature and recommendations for these populations.

Firefighters With Higher Cardiorespiratory Fitness Demonstrate Lower Markers of Cardiovascular Disease Risk.

OBJECTIVE: High cardiorespiratory fitness (CRF) is associated with reduced markers of oxidative stress and cardiovascular disease (CVD) risk factors; however, this relationship has not been elucidated in firefighters. The purpose of this study was to examine differences in markers of CVD risk between firefighters who have either high or low levels of CRF. METHODS: Forty-six firefighters participated in a maximal graded exercise test and a dual-energy x-ray absorptiometry scan and provided a fasted blood sample. V˙O 2max values were categorized based on American College of Sports Medicine guidelines to establish high- and low-fitness groups. RESULTS: High fitness firefighters demonstrated significantly higher high-density lipoprotein cholesterol and lower markers of CVD risk: cholesterol, triglycerides, low-density lipoprotein cholesterol, insulin, homeostatic model assessment for insulin resistance, C-reactive protein, and advanced oxidation protein products concentrations. CONCLUSION: Firefighters are encouraged to maintain high CRF to reduce risk of CVD.

Virtual Reality Based Active Shooter Training Drill Increases Salivary and Subjective Markers of Stress.

Law enforcement personnel are required to respond to a variety of dangerous, potentially life-threatening high stress scenarios. Virtual reality (VR)-based training has been shown to attenuate stress responses; however, little is known about the acute stress response from VR exposure. This study examined the impact of participating in a VR-based active shooter training drill (ASD) on markers of physiological stress as well as potential differences in men and women. To examine the impact of participation in a ~50 sec VR-based ASD, 29 subjects (n = 29; 17 males, 12 females) participated in a quasi-experimental single group design. Saliva samples were collected and analyzed from 27 of the 29 subjects a total of four times 1) 30-min prior to, 2) 5-min prior to, 3) 5-min after, and 4) 30-min after the ASD and analyzed for α-amylase (AA) activity and concentrations of secretory immunoglobulin-A (SIgA), cortisol (CORT), and uric acid (UA). Participation in the ASD resulted in a significant (p < 0.05) increase in salivary stress markers AA and SIgA. In addition, lower concentrations of CORT and UA were found in women compared to men. These findings have implications for law enforcement and/or military personnel that may seek to implement a VR-based training into their training regimen. Future studies should investigate the impact of longitudinal participation in ASD interventions to determine if this is an effective training method to reduce stress responses to real life active shooter training drills.

No Effect of a Ketone Monoester on Markers of Stress and Performance in a Live-Burn Search and Rescue in Firefighters.

ABSTRACT: Waldman, HS, Bryant, AR, Shepherd, BD, Egan, B, and McAllister, MJ. No effect of a ketone monoester on markers of stress and performance in a live-burn search and rescue in firefighters. J Strength Cond Res 36(3): 763-771, 2022-Firefighters experience a range of stressors that impair performance and elevate the risk for developing cardiometabolic diseases. ß-Hydroxybutyrate (ßHB) has been shown to mitigate markers of oxidative stress and inflammation and serve as an alternative fuel with implications to physical performance. On 2 occasions in a double-blind, counterbalanced, and crossover design, 14 professional firefighters performed a live-burn, search and rescue (S&R) 30 minutes after ingestion of a ketone monoester (KME; 0.5 g·kg-1) or a placebo (PLA). Dependent variables collected before and after the S&R included salivary markers of stress and inflammation (cortisol, α-amylase, interleukin-1 beta, uric acid), perceptual markers (profile of mood state [POMS]), gastrointestinal distress (GI), rating of perceived exertion [RPE]), time to completion, and capillary blood measurement of ßHB and glucose. KME resulted in capillary ßHB concentrations of approximately 2.1-3.2 mM throughout the protocol. Capillary glucose concentrations were lower for the KME compared with PLA (∼7%) (interaction effect, p < 0.001). Salivary markers of stress, GI, and time to complete the S&R (∼10 minutes) did not differ between trials, although KME ingestion resulted in significantly higher RPE after the live-burn S&R (KME,6 ± 1; PLA, 4 ± 1). However, POMS data showed the KME also lowered subjective states of nervousness (KME, 0.0 ± 0.0; PLA, 0.6 ± 0.8) and anxiety (KME, 0.0 ± 0.0; PLA, 0.6 ± 0.7) before the S&R (all p < 0.05; large effect sizes). Compared with PLA, ingestion of a KME by firefighters did not mitigate the rise in various markers of salivary stress or impact physical performance during a live-burn S&R. However, differences in RPE and POMS variables were observed, suggesting a possible cognitive role for ßHB.

Impact of Time Restricted Feeding on Markers of Cardiometabolic Health and Oxidative Stress in Resistance-Trained Firefighters.

ABSTRACT: McAllister, MJ, Gonzalez, AE, and Waldman, HS. Impact of time restricted feeding on markers of cardiometabolic health and oxidative stress in resistance-trained firefighters. J Strength Cond Res 36(9): 2515-2522, 2022-Firefighters are often exposed to numerous occupational stressors that cause inflammation, oxidative stress (OS), and elevated risk for developing cardiometabolic disease. Time-restricted feeding (TRF) has been shown to result in favorable changes in markers of inflammation and cardiometabolic health. This study investigated the impact of a 6-week TRF intervention (14:10; fasting:feeding) in resistance-trained firefighters. Blood was analyzed for several markers of inflammation, OS, and cardiometabolic health: insulin, ghrelin, leptin, glucagon, adiponectin, resistin, advanced glycated end products (AGE), advanced oxidation protein products, total nitrite-nitrate levels, tumor necrosis factor-α, interleukin (IL)-6, IL-8, IL-10, as well as glucose and lipid levels. A graded exercise test was also conducted before and after the TRF intervention, and substrate oxidation rates were calculated and compared before and after the intervention. Comparisons pre and post TRF were determined with dependent t -tests. Time-restricted feeding resulted in significant reductions in advanced oxidation protein products (∼31%) and AGEs (∼25%); however, no other changes were found. These findings suggest that TRF may be a nutrition intervention aimed at improving some select markers of cardiometabolic health in firefighters, namely, by the reductions in advanced oxidation protein products and AGEs.

Acute Resistance Exercise Reduces Postprandial Lipemia and Oxidative Stress in Resistance-Trained Men.

ABSTRACT: McAllister, MJ, Steadman, KS, Renteria, LI, Case, MJ, Butawan, MB, Bloomer, RJ, and McCurdy, KW. Acute resistance exercise reduces postprandial lipemia and oxidative stress in resistance-trained men. J Strength Cond Res 36(8): 2139-2146, 2022-Acute ingestion of a high-fat meal (HFM) results in significant increases in postprandial triacylglycerols (TAG) and markers of oxidative stress (OS). Combined aerobic and resistance exercise can attenuate postprandial lipemia; however, it is not clear if acute resistance exercise alone can reduce postprandial OS. The purpose of this study was to determine if acute resistance exercise can attenuate postprandial OS and to compare the effects of moderate versus high-intensity resistance exercise in this regard. Nine ( n = 9) moderately resistance-trained individuals completed 3 testing conditions in a randomized order as follows: (a) rest (no exercise), (b) moderate intensity (3 sets of 10 repetitions at 68% 1 repetition maximum [RM]), and (c) high-intensity resistance exercise (4 sets of 6 repetitions at 85% 1RM). Exercises included barbell back squat, bench press, straight leg deadlift, lat pull-down, upright row, and sit-ups. A HFM was ingested 12 hours after each condition. Blood samples were collected immediately before as well as 2 and 4 hours after ingestion and analyzed for TAG, cholesterol (CHOL), insulin, malondialdehyde (MDA), total nitrate/nitrite (NOx), glutathione (GSH), and advanced oxidation protein products (AOPP). When comparing 4 hour area under curve (AUC) data between conditions, AOPP demonstrated a significantly lower AUC after the moderate-intensity condition compared with resting condition. In addition, resistance exercise resulted in significantly higher plasma NOx concentrations as well as lower TAG and CHOL concentrations after HFM ingestion. Resistance exercise also prevented a decline in GSH that was induced by the HFM. These results demonstrate that acute resistance exercise can attenuate postprandial OS.

Astaxanthin Supplementation Increases Glutathione Concentrations but Does Not Impact Fat Oxidation During Exercise in Active Young Men.

This study investigated the effects of 6 mg/day of astaxanthin supplementation on markers of oxidative stress and substrate metabolism during a graded exercise test in active young men. A double-blind, randomized, counterbalanced, cross-over design was used. Fourteen men (age = 23 ± 2 years) supplemented with 6 mg/day of astaxanthin and a placebo for 4 weeks, with a 1 week washout period between treatments. Following each supplementation period, a fasting blood sample was obtained to measure markers of oxidative stress: glutathione, hydrogen peroxide, advanced oxidation protein products, and malondialdehyde. Participants also completed a graded exercise test after each treatment to determine substrate utilization during exercise at increasing levels of intensity. Glutathione was ∼7% higher following astaxanthin compared with placebo (1,233 ± 133 vs. 1,156 ± 185 µM, respectively; p = .02, d = 0.48). Plasma hydrogen peroxide and malondialdehyde were not different between treatments (p > .05). Although not statistically significant (p = .45), advanced oxidation protein products were reduced by ∼28%. During the graded exercise test, mean fat oxidation rates were not different between treatments (p > .05); however, fat oxidation decreased from 50 to 120 W (p < .001) and from 85 to 120 W (p = .004) in both conditions. Astaxanthin supplementation of 6 mg/day for 4 weeks increased whole blood levels of the antioxidant glutathione in active young men but did not affect oxidative stress markers or substrate utilization during exercise. Astaxanthin appears to be an effective agent to increase endogenous antioxidant status.

Time Restricted Feeding Reduces Inflammation and Cortisol Response to a Firegrounds Test in Professional Firefighters.

OBJECTIVE: Firefighters are at a heightened risk for developing cardiovascular disease. The purpose of this study was to determine if time restricted feeding (TRF) can improve the stress/inflammatory response to a simulated firegrounds test (FGT) in professional firefighters. METHODS: Thirteen firefighters participated in an 8-week TRF intervention (14:10 [fasting:feeding]) protocol and completed a FGT before and after the intervention. Blood lactate, heart rate, salivary C-reactive protein (CRP), interleukin-6 (IL-6), interleukin 1-ß (IL-1ß), and cortisol were measured pre and post FGT. RESULTS: Following TRF, the salivary cortisol response to the FGT was significantly (P < 0.05) reduced. Salivary IL-6 and IL-1ß were also significantly lower, and CRP was higher following the intervention. CONCLUSIONS: These findings demonstrate lower inflammation and reduced stress response to FGT following TRF and may suggest implications in terms of cardiometabolic benefits for firefighters.

Impact of Time Restricted Feeding on Fitness Variables in Professional Resistance Trained Firefighters.

Firefighters are at an elevated risk for cardiometabolic disease and sudden cardiac death due to physiological and psychological stressors. Research suggests time restricted feeding (TRF) may improve health and performance variables. OBJECTIVE: This study investigated the effects of a 7-week TRF (14-hour fasting:10-hour eating window) on fitness variables related to physical health and performance among professional, resistance-trained firefighters. METHODS: Several fitness variables were assessed pre- and post-TRF intervention. RESULTS: Relative and absolute ventilatory threshold (VT) increased (P < 0.05), relative and absolute , decreased (P < 0.05), and muscular strength, endurance, and power were not affected pre- versus post-intervention. CONCLUSION: Although , decreased, all other performance variables were not negatively impacted by TRF. Improvements in VT may be associated with improvements to markers of endurance exercise performance in firefighters, but more data are needed to confirm this hypothesis.

Women demonstrate lower markers of stress and oxidative stress during active shooter training drill.

It has been well documented that police officers are frequently engaged in a variety of high stress situations during their normal daily tasks, such as civilian encounters where force is needed or domestic violence situations, that cause significant increases in a variety of physiological and psychological stress markers. Chronic exposure to stressors increases risk for cardiovascular disease (CVD) progression. The purpose of this study was to compare male and female salivary and blood markers of stress in response to an active shooter training drill (ASD) to determine if acute stress differentially impacts men and women to better understand if interventions should be targeted. Thirty-one participants (males â€‹= â€‹15 [mean age: 23], females â€‹= â€‹16 [mean age: 21]) participated in an ASD involving professional actors playing the role of one active gunman, as well as four victims. The ASD lasted approximately 50 seconds. Blood samples were collected 15 â€‹min prior as well as after the ASD and analyzed for epinephrine (EPI), norepinephrine (NE), and hydrogen peroxide (H2O2) levels. Saliva samples were collected 30 and 5 â€‹min prior to the ASD and 5 and 30 â€‹min after the ASD, and were analyzed for cortisol, α-amylase, uric acid, and secretory immunoglobulin-A (SIgA). Our analysis revealed that acute (~50 â€‹sec) psychological stress in the form of an ASD resulted in significant increases in blood and salivary stress and oxidative stress markers in both men and women. However, four of the seven markers were lower in female participants (cortisol, uric acid, H2O2, and α-amylase presented significant main effects for sex). In addition, SIgA was significantly lower in women compared to men 30 â€‹min prior to, and five min post ASD. These findings suggest females may be at a lower risk to stress induced oxidative stress and CVD.