This review provides evidence that PRT is an effective intervention for improving physical functioning in older people, including improving strength and the performance of some simple and complex activities. However, some caution is needed with transferring these exercises for use with clinical populations because adverse events are not adequately reported.
Exercise training and heart rate variability in older adult female subjects.
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).
                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.
                15 subjects were randomized to endurance trained (ET), 15 subjects to strength training (ST), and 15 subjects to no training (NT) for six months.
                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.
                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.