Systolic Blood Pressure Response to Exercise in Relation to Oxygen Uptake in Endurance Athletes

Sammanfattning: Background: During incremental exercise, systolic blood pressure (SBP) increases due to increasing cardiac output. However, the impact of workload on SBP has often been overlooked. Indexing the increase in SBP to the increase in workload could provide a way of accounting for this. Athletes often reach higher maximal SBP (SBPmax) than untrained subjects, which has been attributed to their superior cardiac capacity. How this affects the relation between SBP and workload is not established. Aim: We sought to characterise the novel metrics SBP/VO2-slope and SBP/Watt-slope in endurance athletes and to analyse possible correlations between these metrics and maximal oxygen uptake (VO2max) in a population of endurance athletes and healthy, non-athletic subjects. We also sought to compare the SBP response of athletes to values predicted by newly published reference equations accounting for workload. Methods: In 24 endurance athletes and 5 healthy non-athletes we assessed the workload-indexed blood pressure response during a graded bicycle ergometer test. SBPmax was defined as the last SBP during exercise, VO2max as the mean of the two highest consecutive VO2 measurements at end of exercise. Results: The mean SBP/VO2-slope was 31.1 ± 9.7 mmHg/l/min and the mean SBP/Watt-slope was 0.28 ± 0.08 mmHg/Watt. We found no significant correlation between VO2max and the SBP/VO2-slope or the SBP/Watt-slope, nor with SBP at 50 W or at 200 W. In males there was a significant correlation between VO2max and SBPmax. The endurance athletes had less steep SBP/Watt-slopes and higher SBPmax than predicted by reference equations.  Conclusion: The SBP/VO2-slope offers a precise way of indexing blood pressure to workload and could provide a valuable tool in future studies investigating the SBP response to exercise. Our results suggest that different reference equations than in the general population might be needed when evaluating the SBP response in athletes.