Continuous Cardiac Autonomic and Haemodynamic Responses to Isometric Exercise

PURPOSEElevated arterial blood pressure (BP) is associated with autonomic dysfunction and impaired haemodynamic control mechanisms. Isometric exercise (IE) training has been demonstrated effective at reducing BP; however, the continuous cardiovascular responses during IE are underinvestigated. We hypothesized that reflex autonomic cardiovascular control is an important mediator in reducing BP. To test our hypothesis, we investigated continuous cardiac autonomic modulation and baroreceptor reflex sensitivity (BRS) in response to IE. METHODSTwenty-five pre-hypertensive participants performed a single IE wall squat training session. Total power spectral density of heart rate variability (HRV) and associated low frequency (LF) and high-frequency (HF) power spectral components, were recorded in absolute (ms) and normalised units (nu) pre, during and post an IE session. Heart rate (HR) was recorded via electrocardiography and BRS via the sequence method. Continuous blood pressure was recorded via the vascular unloading technique and stroke volume via impedance cardiography. Total peripheral resistance (TPR) was calculated according to Ohm’s Law. RESULTSDuring IE there were significant reductions in HRV (p