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.

Questionnaire-Based Prevalence of Physical Activity Level on Adults According to Different International Guidelines: Impact on Surveillance and Policies.

BACKGROUND: The World Health Organization recommends 150 minutes of moderate to vigorous physical activity (PA) throughout the week. However, the weekly frequency of PA and how to combine moderate and vigorous PA to define who reaches the recommended PA are controversial. PA level might be highly different based on the recommendation and/or the criteria employed. METHODS: Demographic data and PA level evaluated by International Physical Activity Questionnaire from 3 random and representative samples from 1 state, 1 city, and 1 local organization in Brazil were analyzed (n = 2961). Nine criteria from different recommendations were used to define PA level. Prevalence estimates and 95% confidence intervals of sufficient PA were calculated for each criterion and compared with the referent (World Health Organization guideline). Total agreement, sensitivity, and specificity were also calculated with 95% confidence interval. RESULTS: When a weekly frequency of PA was required, the prevalence of sufficient PA decreased by 11% (P < .05). For all criteria, doubling the vigorous PA minutes was similar to simply adding them to moderate PA. These findings are consistent regardless of sex, age, and educational level. CONCLUSION: Prevalence estimates and agreement between different PA recommendations were significantly affected when a minimum frequency was required but did not change when vigorous PA minutes were doubled.

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.

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.