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Continuous Cardiac Autonomic and Haemodynamic Responses to Isometric Exercise.
Medicine and Science in Sports and Exercise 2017 March 28
PURPOSE: Elevated 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.
METHODS: Twenty-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.
RESULTS: During IE there were significant reductions in HRV (p<0.05) and BRS (p<0.05) and significant increases in HR (p<0.001), systolic, diastolic, and mean BP (all p<0.001). In recovery from IE, HRV (p<0.001) HFnu (p<0.001) and BRS (p<0.001) significantly increased with a significant decrease in LFnu (p<0.001) and LF:HF ratio (p<0.001), indicative of predominant parasympathetic over sympathetic activity. This autonomic response was associated with a significant reduction in systolic (23.2±18.1 mmHg, p<0.001), diastolic (18.7 ± 16.9 mmHg, p<0.001) and mean (15.8±15.5 mmHg, p<0.001) BP, below baseline and a significant reduction in TPR (p<0.001).
CONCLUSIONS: A single IE session is associated with improved cardiac autonomic modulation and haemodynamic cardiovascular control in pre-hypertensive males. These acute responses may be mechanistically linked to the chronic reductions in resting BP reported following IE training interventions.
METHODS: Twenty-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.
RESULTS: During IE there were significant reductions in HRV (p<0.05) and BRS (p<0.05) and significant increases in HR (p<0.001), systolic, diastolic, and mean BP (all p<0.001). In recovery from IE, HRV (p<0.001) HFnu (p<0.001) and BRS (p<0.001) significantly increased with a significant decrease in LFnu (p<0.001) and LF:HF ratio (p<0.001), indicative of predominant parasympathetic over sympathetic activity. This autonomic response was associated with a significant reduction in systolic (23.2±18.1 mmHg, p<0.001), diastolic (18.7 ± 16.9 mmHg, p<0.001) and mean (15.8±15.5 mmHg, p<0.001) BP, below baseline and a significant reduction in TPR (p<0.001).
CONCLUSIONS: A single IE session is associated with improved cardiac autonomic modulation and haemodynamic cardiovascular control in pre-hypertensive males. These acute responses may be mechanistically linked to the chronic reductions in resting BP reported following IE training interventions.
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