R. S. Zuttin

Avaliação da modulação autonômica da freqüência cardíaca nas posturas supina e sentada de homens jovens sedentários

OBJECTIVE: To evaluate and compare the autonomic heart rate (HR) modulation, under resting conditions in relation to body posture, in sedentary young adults. METHODS: Twenty young healthy and sedentary men aged 22.6 ± 2.5 years participated in the study. The HR and R-R intervals (in ms) of the electrocardiogram (EKG) were obtained in real time using the modified DII derivation, with the volunteers at rest in the supine and seated positions, for 15 minutes. The R-R data were analyzed in the time domain, by means of the RMSSD, RMSM and pNN50 (%) indices; and in the frequency domain, by means of spectral analysis and fast Fourier transforms (FFT), using low frequency (LF) and high frequency (HF) bands expressed as normalized units and as the LF/HF ratio. The statistical analysis consisted of the Spearman test for correlation analyses and the Wilcoxon test for paired samples, with significance of a= 5%. RESULTS: In the time domain, the RMSSD and pNN50 indices demonstrated statistically significant differences between the supine and seated positions (p 0.05). In the frequency domain, the LF and HF bands and the LF/HF ratio demonstrated statistically significant differences between the supine and seated positions (p< 0.05). CONCLUSIONS: The results demonstrated that, by changing the posture, autonomic adjustments were produced to the parasympathetic and sympathetic nervous systems with regard to HR control. This can be attributed to the integrity of the neurocardiac system.

Analysis of heart rate variability in polycystic ovary syndrome

Objective. To compare the modulation of heart rate in a group of volunteers with polycystic ovary syndrome (PCOS) to that of a group of healthy ovulatory women on the basis of R-R interval variability and analyze the relationships between heart rate variability (HRV) and other cardiovascular risk factors. Methods. In a cross-sectional study, HRV and anthropometric, biochemical and hormonal parameters were measured in 23 women with PCOS and 23 age-matched controls. Mean outcomes measures: HRV indexes in the time (SDNN and rMSSD) and frequency domain (low frequency–LF and high frequency–HF). Differences between groups and correlation analysis were performed. Results. Intergroup analysis showed significant differences (p < 0.05) between groups, with lower SDNN, rMSSD, LF and HF indexes in PCOS women when compared to the control group. There was significant negative correlation between BMI and SDNN, LF and HF, indicating a decrease in the autonomic modulation of heart rate with increasing weight. A negative correlation was also found between the high-sensitivity C-reactive protein level and the rMSSD index. Conclusion. Our results show that PCOS is associated with alterations in the autonomic modulation of heart rate, possibly due to the influence of weight gain.

Influência do uso de contraceptivos orais nos níveis lipídicos e nas respostas cardiorrespiratórias de mulheres saudáveis e sedentárias

OBJECTIVE: To evaluate the influence of oral contraceptive use on lipid levels, heart rate (HR) variability and aerobic capacity among sedentary young women. METHODS: The subjects were 20 healthy women (23.55±1.88 years): ten used oral contraceptives (TG) and ten did not (CG). Ergospirometric test on a cycle ergometer was used to determine the aerobic capacity at the anaerobic threshold and at the exercise peak. In addition, recordings of HR and R-R (iRR) intervals in the supine and seated positions, for 15 minutes, and biochemical blood analysis were performed. The iRR (ms) indices were analyzed in the time domain (TD) for RMSSD, RMSM and pNN50 (%), and in the frequency domain (FD) using fast Fourier transforms from low (LF) and high (HF) frequency bands in normalized units, obtaining the LF/HF ratio. Mann-Whitney and Kruskal-Wallis, with α=5%, were used for statistical analyses. RESULTS: The triglyceride and cholesterol levels in the TG were greater than those in the CG (p<0.05). At the anaerobic threshold and at the exercise peak, the power (W), oxygen uptake (VO2), carbon dioxide production (VCO2), (VO2/VCO2) ratio, pulmonary ventilation and HR were not significantly different between the groups. The indices for HR variability in the TD and FD for the two groups in the supine and seated positions were also not different. CONCLUSIONS: The use of oral contraceptives did not influence the aerobic capacity or the autonomic modulation of the HR. However, it influenced the total cholesterol and triglyceride levels. These assessments are important for determining protocols for physical training for cardiovascular disease prevention.

Effect of low-dose combined oral contraceptive on aerobic capacity and anaerobic threshold level in active and sedentary young women

BACKGROUND The purpose of this study was to evaluate the effect of long-term use of oral contraceptives (OC) containing 0.20 mg of ethinylestradiol (EE) combined with 0.15 mg of gestodene (GEST) on the peak aerobic capacity and at the anaerobic threshold (AT) level in active and sedentary young women. STUDY DESIGN Eighty-eight women (23+/-2.1 years old) were divided into four groups - active-OC (G1), active-NOC (G2), sedentary-OC (G3) and sedentary-NOC (G4) - and were submitted to a continuous ergospirometric incremental test on a cycloergometer with 20 to 25 W min(-1) increments. Data were analyzed by two-way ANOVA with Tukey post hoc test. Level of significance was set at 5%. RESULTS The OC use effect for the variables relative and absolute oxygen uptake VO(2) mL kg-(1) min(-1); VO(2), L min(-1), respectively), carbon dioxide output (VCO(2), L min(-1)), ventilation (VE, L min(-1)), heart rate (HR, bpm), respiratory exchange ratio (RER) and power output (W) data, as well as the interaction between OC use and exercise effect on the peak of test and at the AT level did not differ significantly between the active groups (G1 and G2) and the sedentary groups (G3 and G4). As to the exercise effect, for all variables studied, it was noted that the active groups presented higher values for the variables VO(2), VCO(2), VE and power output (p<.05) than the sedentary groups. The RER and HR were similar (p>.05) at the peak and at the AT level between G1 vs. G3 and G2 vs. G4. CONCLUSIONS Long-term use of OC containing EE 0.20 mg plus GEST 0.15 mg does not affect aerobic capacity at the peak and at the AT level of exercise tests.

Efeito de um programa de treinamento de facilitação neuromuscular proprioceptiva sobre a mobilidade torácica

The purpose of this study was to analyse the effect of an upper limb training program based on proprioceptive neuromuscular facilitation (PNF) techniques on thoracic mobility. The study was carried out with 24 sedentary female volunteers, aged 22.9±2.9 years. Participants were divided into a control group (CG), who did not perform any exercise, and a trained group (TG), submitted to training. The physical training protocol consisted of a PNF exercise program, three times a week for four weeks. The two groups were assessed as to thoracic mobility by means of cirtometry before and after the training period. Data were statistically analysed and significance level set at α=5%. In CG, initial axillary and xiphoid cirtometry values showed no significant differences when compared to data obtained on the final evaluation (p>0.05). TG measures, in turn, were significantly higher after the training program (p<0.05). The PNF protocol here proposed seems hence to be an efficient exercise program to promote increase in cirtometry values within a short period of time, suggesting that the it may be used as a physical therapy resource for the development of thoracic mobility.

Adaptações do sistema respiratório referentes à função pulmonar em resposta a um programa de alongamento muscular pelo método de reeducação postural global

The aim of this study was to analyse the respiratory system adaptations concerning pulmonary function in response to stretching the respiratory muscle chain, by means of Global Posture Reeducation (GPR). Twenty sedentary young men with similar anthropometry and no history of musculoskeletal or cardiorespiratory disease were randomly divided into two groups of ten each: control group (CG), who did no stretching, and treated group (TG), submitted to GPR. Stretching was carried out twice a week for 8 weeks, in a total of 16 sessions. The two groups were submitted to pulmonary function tests to assess slow vital capacity, forced vital capacity and maximal voluntary ventilation, before and after the intervention period. The initial values of all spirometric variables measured in CG volunteers showed no statistically significant differences when compared to those of the final evaluation (p>0.05), whereas in TG all values increased after intervention (p<0.05). The GPR respiratory muscle chain stretching protocol thus proved efficient to promote an increase in spirometric variables, suggesting that it may be used as an auxiliary resource in respiratory physical therapy.

Spectral Analysis of Heart Rate Variability in Women

Heart activity is largely modulated by the autonomic nervous system (ANS), which promotes rapid adjustments in the cardiovascular system during different stimuli (i.e., physical exercise, mental stress and postural change) (Hainsworth, 1998). HRV is a noninvasive measure used to analyze the influence of the autonomic nervous system on the heart, providing information about both sympathetic and parasympathetic contributions to consecutive heart rate (HR) oscillations. It has been proposed that a decrease in HRV is a powerful predictor of morbidity and mortality resulting from arrhythmic complications. HRV decreases with age (Catai et al., 2002; Melo et al., 2005) as a consequence of parasympathetic reduction and predominance of sympathetic modulation (Lipsitz et al., 1990; Longo & Correia, 1995; Akselrod, 1995).

Associations between heart rate recovery dynamics with estradiol levels in 20 to 60 year-old sedentary women

It is hypothesized that estradiol levels, as well as aging, influence cardiac autonomic function in women. The main aim of this study was to test the correlations between heart rate recovery (HRR) dynamics, as a proxy of cardiac autonomic function, with estradiol levels and age in women. This cross-sectional study involved 44 healthy women. Heart rate (HR) data were obtained beat-by-beat during the entire experiment. Maximal incremental exercise testing (IET) on a cycle ergometer was performed followed by 6 min of recovery. During the IET recovery period, the overall HRR dynamics were evaluated by exponential data modeling (time constant “τ”) where shorter τ indicates faster HRR adjustment. Considering the cardiac autonomic complexity, HRR dynamics were also evaluated by delta (Δ) analysis considering different HR data intervals. The relationship between HRR dynamics, estradiol levels and age was tested by Pearson product-moment correlation. The overall HRR dynamics (i.e., τ) were statistically correlated with age (r = 0.58, p < 0.001) and estradiol levels (r = -0.37, p = 0.01). The Δ analysis showed that the slower overall HRR associated with aging was a consequence of slower dynamics occurring within the 45–210 s interval, indicating slower sympathetic withdrawal. In conclusion, aging effects on HRR in women seems to be correlated with a slower sympathetic withdrawal. In addition, the cardioprotective effect previously associated with estradiol seems not to influence the autonomic modulation during exercise recovery periods in women.