Markers of isometric training intensity and reductions in resting blood pressure

In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torque(peak)) and peak heart rate peak (HR(peak)) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HR(peak)), heart rate (HR(train)), torque (Torque(train)), and changes in EMG amplitude (ΔEMG(amp)) and frequency (ΔEMG(freq)) were determined. The markers of training intensity were: Torque(train) relative to the 2min-torque(peak) (%2min-torque(peak)), EMG relative to EMG(peak) (%EMG(peak)), HR(train) ΔEMG(amp), ΔEMG(freq), and %MVC. Mean systolic (-4.9 mmHg) and arterial blood pressure (-2.7mmHg) reductions correlated with %2min-torque(peak) (r = -0.65, P = 0.02 and r = -0.59, P = 0.03), ΔEMG(amp) (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMG(freq) (r = -0.67, P = 0.01 and r = -0.64, P = 0.02), and %EMG(peak) (systolic blood pressure only; r = -0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.