Background: Evaluation of non-pharmacological therapies that improve the autonomic control of heart rate of older subjects has a clinical significance, since reduced heart rate variability (HRV) can be associated with higher cardiovascular morbidity and mortality rates.
Objective: To investigate if strength training (ST) improves cardiac autonomic control in healthy older men. Methods: The HRV of 9 older healthy men (62±2.0 years) was evaluated before and after 12 weeks of isokinetic eccentric ST (2 days/week, 2-4 sets of 8-12 repetitions at 75-80% peak torque (PT), involving knee flexion and extension. Electrocardiogram was continuously recorded for 15 min. at rest, in the supine and seated position, before and after the ST period. To estimate strength gains, the eccentric PT of the dominant leg was measured at 60°/sec. by the same isokinetic dynamometer.
Results: Systolic blood pressure decreased (123.78±8.3 to 117.67±10.2 mmHg, P<0.05) and PT increased (extension: 210.02±38.5 to 252.71±60.9 N.m; flexion: 117.56±25.1 to 132.96±27.3 N.m, P<0.05) after the ST. The frequency domain indices showed a significant training effect (P<0.05), since low frequency in normalized units and low frequency/high frequency ratio increased (supine: 57±14 to 68±14, 1.56±.85 to 2.35±1.48; seated: 65±15 to 74±8.0, 2.48±1.09 to 3.19±1.31, respectively), and high frequency in normalized units decreased (supine: 43±14 to 32±14; seated: 35±15 to 26±8) after the training period.
Conclusion: The results of the present investigation suggest that high eccentric strength training performed by older healthy men, increases PT and reduces systolic blood pressure. However, an autonomic imbalance towards sympathetic modulation predominance was induced by an unknown mechanism.
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