AUTHOR=Bjerre-Bastos Jonathan J. , Sejersen Casper , Bihlet Asger R. , Secher Niels H. , Mackey Abigail L. , Kitchen Carl-Christian , Drobinski Patryk , Thudium Christian S. , Nielsen Henning Bay 

TITLE=An Estimate of Plasma Volume Changes Following Moderate-High Intensity Running and Cycling Exercise and Adrenaline Infusion

JOURNAL=Frontiers in Physiology

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2022.948087

DOI=10.3389/fphys.2022.948087

ISSN=1664-042X

ABSTRACT=Introduction: Plasma volume (PV) changes in response to physical activity, possibly as a consequence of adrenergic activation. We estimated changes in PV in response to common exercise modalities; cycling and running as well as adrenaline infusion and a control at rest. 
Methods: On separate days, forty circulatory healthy subjects (aged 60 years (range: 42-75)) with knee osteoarthritis underwent moderate-high intensity cycling, running and intravenous adrenaline infusion to mimic the circulatory response to exercise. Blood samples were obtained from peripheral vein taken at several pre-defined time-points before, during, and after the interventions. PV changes were estimated using venous hemoglobin and the derived hematocrit. The temporal associations between PV and selected biomarkers were explored.
Results: Changes in PV was observed during all four interventions and the response to cycling and running was similar. Compared to rest, PV decreased by -14.3% (95%CI: -10.0 to -18.7) after cycling, -13.9% (95%CI: -10.9 to -17.0) after running, and -7.8% (95%CI: -4.2 to -11.5) after adrenalin infusion. 
Conclusion: PV decreased in response to moderate-high intensity running and cycling. Adrenaline infusion mimicked the PV change observed during exercise suggesting separate influence of autonomic control on blood volume homeostasis. In perspective, a temporal association between PV and biomarker dynamics suggests that consideration of PV changes could be relevant when reporting plasma/serum constituents measured during exercise, but more research is needed to confirm this.