Exercise training and heart rate variability in older adult female subjects.
BACKGROUND
Prior investigations in post-myocardial infarction and healthy elderly subjects have established that heart rate variability (HRV) predicts mortality. Predominantly cross-sectional studies have shown an association between endurance training and measures of HRV. In a randomized trial, this study sought to prospectively compare the effects of endurance and strength training on HRV in 45 healthy elderly females (average age 69.9 +/- 0.9 years).


METHODS
All subjects were rigorously screened to be normal by history, physical, blood tests, ECG, ETT and echocardiogram. All subjects were monitored for 24 hours by a 2-channel Holter before and after training. Artifacts and arrhythmias were manually removed. Tapes were examined for standard measures of HRV.


METHODS
15 subjects were randomized to endurance trained (ET), 15 subjects to strength training (ST), and 15 subjects to no training (NT) for six months.


RESULTS
Training resulted in a significant increase in VO2max in the ET (+7.4%, p = 0.005) group only. There was a small but not significant decrease in HR with both the ET and ST groups. ET resulted in a significant increase in most time domain and all frequency domain measures of HRV. ST resulted in no significant change in HRV measures.


CONCLUSIONS
Strength training, as opposed to endurance training has no significant impact on HRV. This suggests that exercise interventions designed to improve strength (such as weight-lifting) will have little to no impact on HRV, suggesting that aerobic and strength training operate through different mechanisms to reduce cardiac risk.
Madden
Kenneth M
KM
Division of Cardiology, Department of Medicine, Seattle Veterans Affairs Medical Center, Seattle, Washington, USA. kmmadden@interchange.ubc.ca
Levy
Wayne C
WC
Stratton
John K
JK
D000368:Aged; D015992:Body Mass Index; D015444:Exercise; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010101:Oxygen Consumption; D010807:Physical Endurance; D010809:Physical Fitness