Preload to the heart may be limited during rowing because both blood pressure and central venous pressure increase when force is applied to the oar. Considering that only the recovery phase of the rowing stroke allows for unhindered venous return, rowing may induce large fluctuations in stroke volume (SV). Thus, the purpose of this study was to evaluate SV continuously during the rowing stroke. Eight nationally competitive oarsmen (mean ± standard deviation: age 21 ± 2 years, height 190 ± 9 cm, and weight 90 ± 10 kg) rowed on an ergometer at a targeted heart rate of 130 and 160 beats per minute. SV was derived from arterial pressure waveform by pulse contour analysis, while ventilation and force on the handle were measured. Mean arterial pressure was elevated during the stroke at both work rates (to 133 ± 10 [P < .001] and 145 ± 11 mm Hg [P = .024], respectively). Also, SV fluctuated markedly during the stroke with deviations being largest at the higher work rate. Thus, SV decreased by 27 ± 10% (31 ± 11 mL) at the beginning of the stroke and increased by 25 ± 9% (28 ± 10 mL) in the recovery (P = .013), while breathing was entrained with one breath during the drive of the stroke and one prior to the next stroke. These observations indicate that during rowing cardiac output depends critically on SV surges during the recovery phase of the stroke.

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 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 veins 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 were 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 adrenaline infusion.Conclusion: PV decreased in response to moderate-high intensity running and cycling. Adrenaline infusion mimicked the PV change observed during exercise, suggesting a 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.

Volume responsiveness can be evaluated by tilting maneuvers such as head-down tilt (HDT) and passive leg raising (PLR), but the two procedures use different references (HDT the supine position; PLR the semi-recumbent position). We tested whether the two procedures identify "normovolemia" by evaluating the stroke volume (SV) and cardiac output (CO) responses and whether the peripheral perfusion index (PPI) derived from pulse oximetry provides similar information.In randomized order, 10 healthy men were exposed to both HDT and PLR, and evaluations were made also when the subjects fasted. Central cardiovascular variables were derived by pulse contour analysis and changes in central blood volume assessed by thoracic electrical admittance (TEA). During HDT, SV remained stable (fasted 110 ± 16 vs. 109 ± 16 ml; control 113 ± 16 vs. 111 ± 16 ml, p > 0.05) with no change in CO, TEA, PPI, or SV variation (SVV). In contrast during PLR, SV increased (fasted 108 ± 17 vs. 117 ± 17 ml; control 108 ± 18 vs. 117 ± 18 ml, p < 0.05) followed by an increase in TEA (p < 0.05) and CO increased when subjects fasted (6.7 ± 1.5 vs. 7.1 ± 1.5, p = 0.007) with no change in PPI or SVV. In conclusion, SV has a maximal value for rest in supine men, while PLR restores SV as CBV is reduced in a semi-recumbent position and the procedure thereby makes healthy volunteers seem fluid responsive.