Variabilidade da frequencia cardiaca : estudo das influencias autonomicas sobre suas caracteristicas temporal e espectral em halterofilistas e sedentarios

AUTOR(ES)
DATA DE PUBLICAÇÃO

1999

RESUMO

The aim of this study was to investigate the heart rate variability (HRV) in Time (TD) and Frequency (FD) domain in anaerobic, static and isometric exercises, trained individuaIs (weight lifters (WL), n=ll; mean age = 23 ±1,9 years) and healthy untrained subjects (sedentaries (S); n=ll, mean age = 25,5 ± 4,5 years). Volunteers were submitted to: 1) clinical and anthropometric evaluations; 2) continuous exercise protocol in cycle ergometer (15 W/min. increasing, ramp workload until exhaustion) with ECG and ventilatory parameters: ventilation (V), oxygen consumption (V02) and carbon dioxide production (VC02), to determine ventilatory parameters at anaerobic threshold (AT) and peak workload, and 3) 24 hours dynamic electrocardiography (Holter). In dynamic electrocardiography, three or four epochs of 256 seconds each, with signal stability (stationary series), were chosen for analysis, during the following four functional conditions: a) supine rest position in vigil state - one hour, b) vertical static position - 15 minutes, c) habitual sleep and, d) twenty minutes of continuous dynamic exercise in cycle ergometer with workload at 30% below that of anaerobic threshold (AT).Mean and standard deviation (SD) of RR intervals were used for TD analysis, and very low (VLF; 0,003 to 0,04 Hz), low (LF; 0,04 to 0,15 Hz) and high(HF; 0,15 to 0,4 Hz) frequency bands of the spectral decomposition made by fast Fourier transform were used for FD analysis. AIso, LF and HF in normalized units (LFnorm and HFnorm, respectively), LFIHF ratio and total power spectral density (PSD) were computed. The results of anthropometric measures showed only significant (p<0,05) higher values in forearms for WL (median = 30 cm) when compared with S (median = 27 cm). Rest heart rates were similar for both groups while systolic (SAP) and diastolic (DAP) arterial pressure were higher (p<0,05) for WL group than for S group, respectively (median values): SAP = 140 and 120 mmHg; DAP = 100 and 85 mmHg.Ventilatory variables at A T were equal for both groups exeept for the medians of workload (WL = 91,5 W and S = 75,5 W) and VC02 (WL = 1,4 L/min, and S = 0,9 L/min) with p<0,05. In peak workload exercise the median values of V02 (L/min), VC02 and V of the WL group, were significantly (p<0,05) higher than those of the S group.The WL showed greater RR intervals mean values than S (median values) in all functional conditions, but only during supine position (WL = 952,2 ms; S = 829,1 ms) and sleep epochs (WL=1154,0 ms; S=980,0 ms) they were statistically (p<0,05) different. The same significance was obtained for the SD (WL=60,2 ms; S=46,7 ms) during sleep. The FD analysis also showed statistical differences (p<0,05) between the groups, during sleep epochs, with greater HF (absolute values) median values of spectral density (WL=1820,0 ms21Hz; S=898,4 ms21Hz) and total PSD (WL=3542,0 ms21Hz; S=2072,0 ms21Hz) for WL. These results obtained by WL on TD and FD, during habitual sleep, suggest a greater cardiac parasympathetic autonomic activity than SED in this condition.

ASSUNTO(S)

adaptação (fisiologia) sistema cardiovascular educação fisica sistema nervoso autonomo

ACESSO AO ARTIGO

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