The influence of vigorous physical exertion on cardiac demand under conditions of daily living among firefighters with elevated blood pressure.

BACKGROUND: Firefighters have a high prevalence of cardiovascular disease. The poor heart health of firefighters is implicated in their increased risk of sudden cardiac death (SCD). Exercise may be protective against SCD partially due to the immediate blood pressure (BP) reductions of 5-8 mmHg following exercise, termed postexercise hypotension (PEH) OBJECTIVES: To examine PEH under ambulatory conditions after a maximal cardiopulmonary exercise test (CPET) among career firefighters METHODS: Firefighters (n = 19) completed a maximal CPET and non-exercise control (CONTROL) in random order on separate non-workdays and left the laboratory instrumented to an ambulatory BP (ABP) monitor. Ambulatory systolic BP (ASBP), diastolic BP (ADBP), and heart rate (AHR) were recorded at hourly intervals over 19hr. The ambulatory rate pressure product (ARPP) was calculated as ASBPxAHRx10-3 at each hourly interval. Repeated measures ANCOVA tested if the ABP, AHR, and ARPP responses differed after CPET vs CONTROL over 19hr RESULTS: Firefighters were middle-aged (39.5 ± 8.9 yr), overweight (29.2 ± 4.0 kg/m2) men with elevated BP (123.1 ± 9.6/79.8 ± 10.4 mmHg), while resting HR (67.7 ± 11.3 bpm) and RPP (8.4 ± 1.7mmHg*bpm*10-3) were in normal ranges. ASBP (16.6 ± 5.7 mmHg) and ADBP (3.1 ± 4.6 mmHg) increased after the CPET vs CONTROL over 19hr (ps<0.01), as did AHR (9.4 ± 7.9 bpm, p = 0.02) and ARPP (2.5 ± 1.1mmHg*bpm*10-3, p < 0.01). CONCLUSIONS: Unexpectedly, the firefighters exhibited postexercise hypertension rather than PEH. The increases in ABP and AHR we observed indicated a sustained increase in cardiac demand. Further investigation is needed to confirm our findings and determine whether the adverse hemodynamic responses we observed contribute to the high prevalence of SCD that firefighters experience on the job.

Reliability and Time Course of Postexercise Hypotension during Exercise Training among Adults with Hypertension.

Postexercise hypotension (PEH), or the immediate decrease in blood pressure (BP) lasting for 24 h following an exercise bout, is well-established; however, the influence of exercise training on PEH dynamics is unknown. This study investigated the reliability and time course of change of PEH during exercise training among adults with hypertension. PEH responders (n = 10) underwent 12 weeks of aerobic exercise training, 40 min/session at moderate-to-vigorous intensity for 3 d/weeks. Self-measured BP was used to calculate PEH before and for 10 min after each session. The intraclass correlation coefficient (ICC) and Akaike Information Criterion (AIC) determined PEH reliability and goodness-of-fit for each week, respectively. Participants were obese (30.6 ± 4.3 kg∙m-2), middle-aged (57.2 ± 10.5 years), and mostly men (60%) with stage I hypertension (136.5 ± 12.1/83.4 ± 6.7 mmHg). Exercise training adherence was 90.6 ± 11.8% with 32.6 ± 4.2 sessions completed. PEH occurred in 89.7 ± 8.3% of these sessions with BP reductions of 9.3 ± 13.1/3.2 ± 6.8 mmHg. PEH reliability was moderate (ICC ~0.6). AIC analysis revealed a stabilization of maximal systolic and diastolic BP reductions at 3 weeks and 10 weeks, respectively. PEH persisted throughout exercise training at clinically meaningful levels, suggesting that the antihypertensive effects of exercise training may be largely due to PEH. Further studies in larger samples and under ambulatory conditions are needed to confirm these novel findings.