Effects of Isometric Handgrip Training on Home Blood Pressure Measurements in Hypertensive Patients: A Randomized Crossover Study

Abstract

Objective We aimed to examine the effects of isometric handgrip (IHG) training on home blood pressure (BP) levels in hypertensive Japanese patients undergoing treatment. Methods Fifty-three hypertensive patients (mean age, 61.7 years; 56.6% men) with a home systolic BP ≥135 mmHg and/or a home diastolic BP ≥85 mmHg were randomly assigned to either group A or B. As per the crossover design, group A performed 8 weeks of IHG training, followed by an equivalent training-free, control period, while the reverse protocol was performed by group B. The baseline characteristics were similar between both groups. The individualized daily IHG training comprised four sets of 2-min isometric contractions at 30% of the individual's maximum voluntary contraction capacity, including 1 min of rest between sets, for ≥3 days/week. The outcome measure was morning and evening home BP readings taken over the last 2 weeks of the training and control periods. Results A combined data analysis for both groups showed that IHG training was significantly associated with the lowering of both systolic and diastolic BP in the morning (137.9±9.3 vs. 135.3±9.5 mmHg, p=0.007 and 83.0±9.5 vs. 81.2±9.3 mmHg, p<0.001, respectively) and evening (130.0±10.7 vs. 127.6±10.1 mmHg, p=0.003 and 75.8±10.4 vs. 73.8±9.2 mmHg, p<0.001, respectively), while no significant change was observed after the control period. A larger increase in the maximum grip strength due to IHG training was associated with greater BP reductions. Conclusion An 8-week period of IHG training significantly lowered both the morning and evening home BP in hypertensive Japanese patients undergoing treatment.

Keywords: grip strength; home blood pressure; hypertension; isometric handgrip training; non-pharmacological treatment.

Figure 1.

Flowchart of the study. All participants duly completed the study protocol. IHG training: isometric handgrip training

Figure 2.

Changes in the home blood pressure values before and after the control and IHG training periods. Each Figure shows (a) morning HSBP, (b) morning HDBP, (c) evening HSBP, (d) evening HDBP. IHG training: isometric handgrip training, HSBP: home systolic blood pressure, HDBP: home diastolic blood pressure. **p<0.01 vs. before.

Figure 3.

Changes in the maximum grip strength before and after the control and IHG training periods. IHG training: isometric handgrip training. *p<0.05 vs. before.

Figure 4.

Changes in the home blood pressure values according to the lower or upper half increase in maximum grip strength during the control or IHG training period. Grip (L) and grip (U) indicate lower and upper half increase in grip strength during a given period. (a), (b), (c), and (d) represent morning HSBP, morning HDBP, evening HSBP, and evening HDBP, respectively. CON: control period of group B, IHG: isometric handgrip training period, HSBP: home systolic blood pressure, HDBP: home diastolic blood pressure. *p<0.05 vs. before, **p<0.01 vs. before.