The effects of a 6-month mandatory military police academy training on recruits' physical fitness.

BACKGROUND: Physical fitness for health and professional performance play important roles in police workforce considering that policing is a dangerous job, associated with high physical demands. OBJECTIVES: (1) To evaluate the effects of a 6-month course of police academy training on health-related physical fitness (HRPF) of military police recruits. (2) To investigate whether recruits' HRPF still met the academy entry standards after an unsupervised 7-month period prior to academy. METHODS: We conducted an observational and longitudinal study with 219 male police recruits (aged 25.5±3.6 years; BMI of 24.4±2.5 kg/m2). HRPF parameters included the Cooper 12-min running test for cardiorespiratory fitness (CRF), curl-ups, pull-ups and push-ups for muscle strength/endurance which were evaluated 3 times: 7 months prior to academy course and pre- and post-academy training period. RESULTS: Participants maintained optimal age-related HRPF during the unsupervised period prior to academy. After academy training upon graduation, all HRPF parameters further increased an average of 7.7 to 69.0% (p < 0.001; calculated Cohen's d effect size ≥0.95). CRF was the only HRPF that improved less than 10% after the academy course. CONCLUSIONS: Police recruits that had passed the application fitness standards maintained their HRPF prior to academy, and all their HRPF parameters increased after a 6-month academy training period which was not primarily focused on exercise training. Among all components of HRPF, CRF appears to be the most challenging one to improve among police recruits. Our findings suggest that regular training with minimum physical standards could be potentially beneficial to police officers' health and career longevity.

Post-exercise heart rate recovery and its speed are associated with cardiac autonomic responsiveness following orthostatic stress test in men.

Objective: The present study sought to expand upon prior investigations of the relationship between the post-exercise heart rate recovery (HRR) and the cardiac autonomic responsiveness after orthostatic stress test.Method: HRR at the 1st, 3rd, and 5th min after maximal exercise test were correlated with relative change (Δ%) of time-domain (CV, pNN50, and rMSSD) and frequency-domain (TP, LF, HF, and LF/HF ratio) indices of heart rate variability (HRV) after active orthostatic test in 46 healthy men. Statistical analysis employed non-parametric tests with a p-value set at 5%.Results: HRR at 1st min correlated with Δ%pNN50 (rs:0.36 - p = .02). In the 3rd and 5th min, these measures correlated with Δ%pNN50, Δ%rMSSD, Δ%CV, Δ%TP, and Δ%HF indices (rs:0.33, 0.59 - p ≤ .05). Coefficient of HRR at the 1st min correlated with Δ%pNN50, Δ%rMSSD, and Δ%HF (rs:0.28, 0.45 - p ≤ .05). The 3rd and 5th min showed correlation with Δ%pNN50, Δ%rMSSD, Δ%HF, Δ%CV, and Δ%TP (rs:0.37, 0.64 - p ≤ .05). No correlation was found with indices combined sympathetic-parasympathetic modulation and HRR. After the sample was divided into high and low parasympathetic responsiveness subgroups after the orthostatic test, faster HRR was associated with the degree of parasympathetic responsiveness (reduction) following postural change (p ≤ .05).Conclusion: HRR throughout the 1st to 5th min is positively correlated with parasympathetic responsiveness and overall cardiac autonomic modulation of HRV after the orthostatic stress test, and faster HRR is positively correlated with the relative degree of parasympathetic responsiveness after the active postural change at rest in healthy men.

Cardiac Autonomic Function in the First Hours of Postnatal Life: An Observational Cross-Sectional Study in Term Neonates.

The aim of this study was to evaluate heart rate variability (HRV) within the first hours of extrauterine life in term neonates. HRV at 2-h and 14-h postpartum were compared by means of time domains (iRR, SDNN, and rMSSD); frequency domains (TP, LF, HF, and LF/HF ratio); and Poincare's Plot (SD1 and SD2) indices of HRV in 27 healthy, male, term newborns (NBs) born of elective cesarean delivery. Within 14 h after birth, the mean of the iRRs increased (Δ% = 4.4, p < 0.001) as well as parasympathetic indices (rMSSD: Δ% = 32.6; p < 0.03; HF: Δ% = 43.6; p < 0.00; SD1: Δ% = 32.6, p < 0.03). Respiratory rate (RR) decreased (RR: 2 h = 48 (43-55) cycle/min vs. 14 h = 45 (40-48) cycle/min p < 0.01). We concluded that within the first 14 h of birth, cardiac autonomic adjustments are characterized by an increase in parasympathetic activity. Concurrently, there were no significant changes observed in all other HRV indices in healthy, male, term neonates, and born of elective cesarean delivery.

Firefighters' basal cardiac autonomic function and its associations with cardiorespiratory fitness.

BACKGROUND: Firefighters' activities require constant adjustments of the cardiovascular system with cardiac autonomic function (CAF) playing an important role. Despite the crucial role of CAF in regulating stress response, little is known about firefighters' CAF. OBJECTIVE: We aimed to characterize the resting on-duty and off-duty CAF of male firefighters, in association with cardiorespiratory fitness (CRF). METHODS: We evaluated 38 firefighters in an on-duty rest condition and 26 firefighters in an off-duty laboratory-controlled condition. CAF was addressed by means of heart rate variability (HRV). We compared HRV measurements between CRF categories (<12METs vs ≥12METs). Wilcoxon, Mann-Whitney texts and Spearman correlation were used and General Linear Model was applied for age and BMI adjustments. RESULTS: Firefighters' resting CAF is characterized by a predominant sympathetic modulation and a large inter-individual dispersion in all HRV indices, in both groups. We found a positive correlation between a higher CRF, the overall CAF and the higher parasympathetic activity (p <  0,03). Firefighters with CRF ≥12 METs showed a higher parasympathetic modulation. CONCLUSIONS: Firefighters' resting CAF is characterized by a predominant sympathetic modulation and a large inter-individual dispersion in all HRV indices, in both groups. Our results support mandatory physical training focused in improving firefighters' CAF as a cardiopretective effect.

Agreement between BMI and body fat obesity definitions in a physically active population.

OBJECTIVES: Body mass index (BMI) is a widely used proxy of body composition (BC). Concerns exist regarding possible BMI misclassification among active populations. We compared the prevalence of obesity as categorized by BMI or by skinfold estimates of body fat percentage (BF%) in a physically active population. SUBJECTS AND METHODS: 3,822 military firefighters underwent a physical fitness evaluation including cardiorespiratory fitness (CRF) by the 12 min-Cooper test, abdominal strength by sit-up test (SUT) and body composition (BC) by BF% (as the reference), as well as BMI. Obesity was defined by BF% > 25% and BMI ≥ 30 kg/m2. Agreement was evaluated by sensitivity and specificity of BMI, positive and negative predictive values (PPV/NPV), positive and negative likelihood (LR+/LR-), receiver operating characteristic (ROC) curves and also across age, CRF and SUT subgroups. RESULTS: The prevalence of obesity estimated by BMI (13.3%) was similar to BF% (15.9%). Overall agreement was high (85.8%) and varied in different subgroups (75.3-94.5%). BMI underestimated the prevalence of obesity in all categories with high specificity (≥ 81.2%) and low sensitivity (≤ 67.0). All indices were affected by CRF, age and SUT, with better sensitivity, NPV and LR- in the less fit and older groups; and higher specificity, PPV and LR+ among the fittest and youngest groups. ROC curves showed high area under the curve (≥ 0.77) except for subjects with CRF ≥ 14 METs (= 0.46). CONCLUSION: Both measures yielded similar obesity prevalences, with high agreement. BMI did not overestimate obesity prevalence. BMI ≥ 30 was highly specific to exclude obesity. Because of systematic under estimation, a lower BMI cut-off point might be considered in this population.

Agreement between BMI and body fat obesity definitions in a physically active population

ABSTRACT Objectives Body mass index (BMI) is a widely used proxy of body composition (BC). Concerns exist regarding possible BMI misclassification among active populations. We compared the prevalence of obesity as categorized by BMI or by skinfold estimates of body fat percentage (BF%) in a physically active population. Subjects and methods 3,822 military firefighters underwent a physical fitness evaluation including cardiorespiratory fitness (CRF) by the 12 min-Cooper test, abdominal strength by sit-up test (SUT) and body composition (BC) by BF% (as the reference), as well as BMI. Obesity was defined by BF% > 25% and BMI ≥ 30 kg/m2. Agreement was evaluated by sensitivity and specificity of BMI, positive and negative predictive values (PPV/NPV), positive and negative likelihood (LR+/LR-), receiver operating characteristic (ROC) curves and also across age, CRF and SUT subgroups. Results The prevalence of obesity estimated by BMI (13.3%) was similar to BF% (15.9%). Overall agreement was high (85.8%) and varied in different subgroups (75.3-94.5%). BMI underestimated the prevalence of obesity in all categories with high specificity (≥ 81.2%) and low sensitivity (≤ 67.0). All indices were affected by CRF, age and SUT, with better sensitivity, NPV and LR- in the less fit and older groups; and higher specificity, PPV and LR+ among the fittest and youngest groups. ROC curves showed high area under the curve (≥ 0.77) except for subjects with CRF ≥ 14 METs (= 0.46). Conclusion Both measures yielded similar obesity prevalences, with high agreement. BMI did not overestimate obesity prevalence. BMI ≥ 30 was highly specific to exclude obesity. Because of systematic under estimation, a lower BMI cut-off point might be considered in this population.

Effect of Body Mass Index on Left Ventricular Mass in Career Male Firefighters.

Left ventricular (LV) mass is a strong predictor of cardiovascular disease (CVD) events; increased LV mass is common among US firefighters and plays a major role in firefighter sudden cardiac death. We aim to identify significant predictors of LV mass among firefighters. Cross-sectional study of 400 career male firefighters selected by an enriched randomization strategy. Weighted analyses were performed based on the total number of risk factors per subject with inverse probability weighting. LV mass was assessed by echocardiography (ECHO) and cardiac magnetic resonance, and normalized (indexed) for height. CVD risk parameters included vital signs at rest, body mass index (BMI)-defined obesity, obstructive sleep apnea risk, low cardiorespiratory fitness, and physical activity. Linear regression models were performed. In multivariate analyses, BMI was the only consistent significant independent predictor of LV mass indexes (all, p <0.001). A 1-unit decrease in BMI was associated with 1-unit (g/m1.7) reduction of LV mass/height1.7 after adjustment for age, obstructive sleep apnea risk, and cardiorespiratory fitness. In conclusion, after height-indexing ECHO-measured and cardiac magnetic resonance-measured LV mass, BMI was found to be a major driver of LV mass among firefighters. Our findings taken together with previous research suggest that reducing obesity will improve CVD risk profiles and decrease on-duty CVD and sudden cardiac death events in the fire service. Our results may also support targeted noninvasive screening for LV hypertrophy with ECHO among obese firefighters.

Body Composition is Strongly Associated With Cardiorespiratory Fitness in a Large Brazilian Military Firefighter Cohort: The Brazilian Firefighters Study.

Firefighting is associated with high-level physical demands and requires appropriate physical fitness. Considering that obesity has been correlated with decreased cardiorespiratory fitness (CRF) and that the prevalence of obesity may also be elevated within firefighters (FF), we analyzed the association between CRF and body composition (BC) in Brazilian military FF. We assessed 4,237 male FF (18-49 years) who performed a physical fitness test that included BC and CRF. Body composition was assessed by body mass index (BMI), body adiposity index (BAI), body fat percentage (BF%), and waist circumference (WC). CRF was assessed by the 12-minute Cooper test. Comparisons of VO2max between the BC categories were analyzed using the Mann-Whitney test, and the analysis was adjusted for age using the General Linear Model. The Spearman test was used for correlation analysis and the odds ratio (OR) was calculated to assess the odds of the unfit group (≤ 12 metabolic equivalents [METs]) for poor BC. Statistically significant differences were considered when p ≤ 0.05. Considering the BMI categories, 8 volunteers (0.2%) were underweight, 1,306 (30.8%) were normal weight, 2,301 (54.3%) were overweight, and 622 (14.7%) were obese. The VO2max was negatively correlated with age (rs = -0.21), BMI (rs = -0.45), WC (rs = -0.50), and BAI (rs = -0.35) (p < 0.001). Cardiorespiratory fitness was lower in the obese compared with the nonobese for all age categories (-3.8 ml · kg(-1) · min(-1); p < 0.001) and for all BC indices (-4.5 ml · kg(-1) · min(-1); p < 0.001). The OR of the unfit group having poor BC in all indices varied from 2.9 to 8.1 (p < 0.001). Despite the metabolically healthy obesity phenomenon, we found a strong association between CRF and BC irrespective of age and the BC method (BMI, BAI, WC, or BF%). These findings may aid in improving FF training programs with a focus on health and performance.

Unaltered R-R interval variability and bradycardia in cyclists as compared with non-athletes.

PURPOSE: To test whether elite mountain bikers display a cardiac autonomic modulation pattern that is distinctive from that of active non-athletes. BACKGROUND: The relationship between autonomic adaptation and bradycardia during physical exercise, including high-performance sports such as the mountain biking, remains to be elucidated. METHODS: Twelve elite mountain bikers and 11 matched non-athletes controls were evaluated for time- and frequency-domain heart rate variability based on a 5-min ECG R-R intervals series obtained in both the supine and the orthostatic positions. Oxygen uptake and pulse rate were obtained at ventilatory thresholds and peak effort during an incremental cardiopulmonary exercise test. Significance of differences between medians (25th, 75th percentiles) from the two groups was evaluated by the Mann-Whitney test at p ≤ 0.05. RESULTS: Athletes had lower heart rate [50 (47, 59) versus 63 (60, 69) bpm; p = 0.0004] and higher cardiopulmonary performance than controls [70.9 (64.6, 74.4) versus 47.7 (41.0, 51.9) mL (kg min)(-1); p = 0.01]. No statistical difference was found in heart rate variability in the group of athletes (p = 0.17-0.97), except for trend toward having lower coefficient of variation and low-frequency absolute power indices both in supine position (p = 0.06). CONCLUSIONS: Bradycardia and higher oxygen uptake were found in association with unaltered cardiac autonomic modulation in elite mountain bikers athletes in supine and orthostatic positions, compared to active non-athletes. This bradycardia was not dependent on distinctive resting autonomic modulation. Intrinsic adaptation of sinus node and/or a peculiar state of autonomic adaptation to this exercise can be possible mechanisms.