Is the Magnitude of Post-Exercise Hypotension Mediated by Exercise Intensity or Total Work Done?

Abstract

It is unclear whether exercise intensity per se or the total work done is the most important factor that influences the magnitude of post-exercise hypotension (PEH). As well as being important for prescribing exercise to hypertensive patients, such knowledge might help unravel the mechanisms of PEH. PURPOSE: To compare post-exercise hemodynamic changes between bouts of exercise which differ in intensity and total work completed. METHODS: Seven normotensive males, aged 28±6 years (mean±SD), completed four trials, which began at 08:00 hours; (i) Control – resting for 30 min on a semi-recumbent cycle ergometer, (ii) Intense – 30-min of semi-recumbent cycling at 70% VO2peak, (iii) Moderate-short; cycling at 40% VO2 ± for 30 min and (iv) Moderate-long; cycling at 40% VO2peak for a time (mean±SD =50±8 min) that corresponded to the same total work done as in the Intense trial. Blood pressure (Portapres, Holland), heart rate, stroke volume, cardiac output, total peripheral resistance, core body temperature and forearm blood flow were measured every min for 5 min before, and for 20 min after, exercise. Data were analysed using repeated measures analysis of summary statistics and are described as mean±SD. RESULTS: Post-exercise hypotension relative to Control was observed in all three exercise trials with the minimum SBP occurring approximately 8 min after cessation of exercise in all trials. The mean reduction in SBP was different to control after Intense (−19± 11 mmHg, P=0.014) and Moderate-long (−15±15 mmHg. P=0.032) but not after Mo derate-short (−9±15 mmHg, P=0.123). Mean arterial pressure followed the same pattern, with Intense (−7±6 mmHg, P=0.057) and Moderate-long (−8±10 mmHg, P=0.048) mediating lower post-exercise MAP than Moderate-short (−5±8 mmHg, P=0.122). No significant differences were observed between the Intense and Moderate-long trials in terms of SBP (P=0.529) and MAP (P=0.727). Increases in HR, CO and FBF were greatest after the Intense trial (35±7 beat.min−1, 1.7±0.8 l.min−1 and 13.6±8.7 PU respectively, p<0.0005). Reductions in SV and TPR were also greatest after Intense (−21.7±16.1 ml and-4.2±2.2mmHg.L−1 min−1, respectively, p<0.001). Core temperature increased by 0.5–0.7 °C, but this change did not differ between the three exercise trials. CONCLUSION: Exercise bouts that differed in intensity but not total work completed induced similar post-exercise responses in SBP and MAP. These similar blood pressure responses were evident despite the changes in HR, CO, SV, TPR and FBF being greatest after the more intense but shorter bout of exercise.