Effect of isometric handgrip training on heart rate variability and blood pressure in frail older adults: a randomized controlled trial

Abstract Objective This study assessed the effect of isometric handgrip training (IHT) on heart rate variability (HRV) and blood pressure (BP) in frail older adults. Methods In this double-blind randomized controlled clinical trial, 33 frail older adults were selected. HRV was recorded using a Polar V800 device, and BP was measured using the auscultatory method. HRV analysis was performed in the time domain using the indices MNN, SDNN, RMSSD, and pNN5, and in the frequency domain using the indices LF (low-frequency band), HF (high-frequency band), and the LF/HF ratio to represent the sympathetic-vagal balance. Participants were divided into two groups: the IHT group (n=18), that participated in a 30-day program performing 32 repetitions of handgrip exercises with a 5-second pause, maintaining maximum contraction for 5 seconds using a rubberized grip device; and the control group (n=15), which performed a series of 12-second stretches of the dominant upper limb. The Wilcoxon test was used to assess statistical significance (p<0.05). Results Of the 509 older adults screened at the Integrated Health Center of São Paulo, 33 completed the study. After the intervention, the IHT group showed a significant decrease in sympathetic modulation (LF index; p<0.001), an increase in parasympathetic modulation (HF index; p<0.002), a reduction in the LF HF ratio (p<0.002), and a trend toward lower systolic BP (p=0.053). No significant changes were observed in the control group. Conclusion Isometric handgrip training was associated with increased HRV in frail older adults, and there was a notable trend toward lower systolic BP in this population.