Efeito do treinamento de força excêntrica no controle autonômico da freqüência cardíaca de idosos durante o repouso e contrações isométricas
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Data
2007-02-26Autor
Takahashi, Anielle Cristhine de Medeiros
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The purpose of the present study was to investigate the effect of eccentric strength training
(ST) on autonomic control of heart rate (HR) evaluated at rest and during isometric exercise.
Nine healthy men (62 ±2 years old) were submitted to 12 weeks of ST for knee extensors and
flexors muscles (2x/week, 2-4 series of 8-12 repetitions, 70-80% of eccentric peak torque).
Before and after the ST, the HR and its variability were evaluated at rest (supine and seated
conditions) and during the sub-maximal isometric contractions (SIC; 15, 30 and 40% of
maximal voluntary contraction) of knee extension wich were performed during 240s or until
exhaustion. The HR was obtained at pre- (60s), during and post SIC (120s). Then, the
variation (∆) between the resting HR and HR at 10, 30, 60s and end of contraction observed
during each SIC was analyzed. The HR variability was evaluated by the RMSSD index,
which was determined in resting condition and during SIC (i.e., two windows of 30s in
duration at the beginning and end of R-R interval data). The ANOVA two-way (repeated
measures) and t-test was utilized for statistical analysis (p < 0.05). The ST increased the
eccentric torque (extension: 210 ± 38 to 252.7 ± 61 N.m, flexion: 117.6 ± 25.1 to 133 ± 27.3
N.m) , but did not change the HR and HR variability at rest (HR supine: 62 ± 11 to 65 ± 9
bpm, HR seated: 62 ± 11 to 66 ± 9, RMSSD supine: 28.5 ± 18 to 21.5 ± 8.4, RMSSD seated:
30.4 ± 2 to 18.9 ± 6.2). The ST did not modify the isometric peak torque (177.6 ± 25 to 195.2
± 31,2 N.m) and the time of execution of each SIC (15%: 240 to 240s, 30%: 203.4 ± 55 to
218 ± 5s, 40%: 135.6 ± 56.7 to 144.6 ± 55.6s). During the SIC, the pattern of HR response
(significative increase in ∆HR from 30s to the end of contraction in 15 and 40%) and the
RMSSD index (significative decrease from the first 30s to the last 30s of contraction in all
levels of effort) was similar for the pre- and post training. Despite the ST increased the
eccentric torque, it did not generate changes in the autonomic control of heart rate at rest and
during the SIC.