The ambulatory blood pressure and heart rate variability responses following sudden vigorous physical exertion among firefighters with hypertension

Objective: To examine postexercise hypotension (PEH) after a maximal cardiopulmonary stress test (GEST) as well as heart rate variability (HRV), a surrogate marker of sympathovagal balance, as it relates to PEH among career firefighters with hypertension. Materials and Methods: Firefighters (n=5) who were middle-aged (40.6±6.2yr) and overweight (28.1±3.9kg.m-2) men with high BP (Systolic 126.4±9.5mmHg/Diastolic 85.6±5.9mmHg) and normal resting HR (71.1±11.2bpm) randomly performed a GEST and non-exercise control (CONTROL) session followed by attachment to ambulatory BP (ABP) and HR monitors for 19hr. Systolic (ASBP) and diastolic (ADBP) ABP, and HRV low (LF) and high (HF) frequency were recorded at hourly intervals over awake (11hr), sleep (8hr), and 19hr. Repeated measure analysis of variance (ANOVA) tested if BP and HRV differed over time and between experimental conditions. Multivariate regression tested the relationship between HRV and BP responses. Results: Compared to CONTROL, after the GEST ASBP significantly increased over awake (21.7±3.4mmHg, p=0.003) and 19hr (15.8±2.2mmHg, p=0.002), and exhibited a statistically trending increase over-sleep (7.9±2.9mmHg, p=0.055). Compared to CONTROL, after the GEST ADBP showed a statistically trending increase over awake (8.8±3.9 mmHg, p=0.091), sleep (8.2±4.3mmHg, p=0.134), and 19hr (8.6±3.5mmHg, p=0.072). Compared to CONTROL, after the GEST LF/HF significantly increased over awake (1.9±0.5, p=0.015), and displayed a statistically trending increase over 19hr (0.8±0.5 p=0.155). LF/HF statistically tended to explain up to 59.3% of the variance in the SBP response over 19hr (r:-0.77, p=0.068) and significantly explained 84.5% of the variance in the DBP response over awake (r:-0.92, p=0.014). Conclusion: Sudden vigorous exertion evoked postexercise hypertension as opposed to PEH among firefighters with elevated BP. Reasons for these unexpected findings are not clear but may reside in a compensatory baroreflex response to sympathetic predominance as reflected by higher LF/HF due to either increased sympathetic or decreased parasympathetic modulation