Blood pressure and cardiac autonomic adaptations to isometric exercise training: A randomized sham-controlled study

Isometric exercise training (IET) is increasingly cited for its role in reducing resting blood pressure (BP). Despite this, few studies have investigated a potential sham effect attributing to the success of IET, thus dictating the aim of the present study. Thirty physically inactive males (n=15) and females (n=15) were randomly assigned into 3 groups. The IET group completed a wall-squat intervention at 95% peak heart rate (HR) using a prescribed knee joint angle. The sham group performed a parallel intervention, but at an intensity (<75% peak HR) previously identified to be inefficacious over a 4-week training period. No-intervention controls maintained their normal daily activities. Pre- and post-measures were taken for resting and continuous blood pressure and cardiac autonomic modulation. Resting clinic and continuous beat to beat systolic (-15.2±9.2 and -7.3±5.6 mmHg), diastolic (-4.6±5 and -4.5±5.1) and mean (-7±4.2 and -7.5±5.3) BP, respectively, all significantly decreased in the IET group compared to sham and no-intervention control. The IET group observed a significant decrease in low frequency normalised units of heart rate variability concurrent with a significant increase in high frequency normalised units of heart rate variability compared to both the sham and no-intervention control groups. The findings of the present study reject a non-specific effect and further support the role of IET as an effective anti-hypertensive intervention.