INTRODUCTION: Control of oxygen uptake (VO2) during the rest-to-exercise transition is thought to be dominated by intracellular processes rather than oxygen delivery. However, large changes in arterial pressure (i.e., supraphysiologic) have been shown to alter VO2 and its kinetics. Importantly, no studies have investigated the consequence of physiologic alterations in blood pressure on VO2 and its kinetics during exercise in humans. PURPOSE: The aim of this preliminary study was to assess the effect of modest reductions in MAP achieved via neck suction upon Vo2 across the rest-exercise transition, to test the hypothesis that physiologic reductions in arterial pressure during moderate intensity, steady-state exercise will not alter VO2. METHODS: Five subjects completed four exercise trials of 6 minute leg cycling at the workloads 50% of VO2max. Each workload was completed with and without carotid baroreceptor loading (i.e., Neck Suction: blood pressure lowering stimulation) with a 20 minute resting period between trials. Heart rate, mean arterial pressure (MAP), and VO2 at the mouth, were continuously measured while upper arm blood pressure was taken every minute. RESULTS: MAP tended to be reduced during the Neck Suction condition (delta MAP: Control 13.0±8.7 vs Neck Suction 6.3±6.3 mm Hg, P=0.079). However, there was no main effect for exercise condition on VO2 (Control 13.25±1.70 vs Neck Suction 13.17±1.72 ml/kg/min, P=0.61). In addition, the on-transient mean response time was not different between groups (Control 46.7±27.2 vs Neck Suction 40.9±16.2 s). CONCLUSIONS: These preliminary findings indicate that oxygen uptake or its kinetics during moderate intensity leg cycling are not affected by modest reductions in blood pressure.
Butts, Cory L.; McDonough, Paul; Keller, David; Samels, Mitchel; and Krnjajic, Davor
"The Impact of Physiologic Reductions In Blood Pressure Upon Oxygen Uptake During Moderate Intensity Leg Cycling,"
International Journal of Exercise Science: Conference Proceedings: Vol. 2
, Article 64.
Available at: http://digitalcommons.wku.edu/ijesab/vol2/iss4/64