Effect of postural control position and blood- sampling arm position on change in plasma volume from supine rest through a cycling bout

The objective of this study was to determine any interaction between a postural control period and bloodsampling arm position on change in plasma volume (ΔPV) from supine rest through a bout of cycling. The subjects underwent two different testing protocols. During the control test, each subject lay supine and then sat upright, each for 30 min before cycling for 20 min at ~70% of age-predicted maximal heart rate (HR max). During the non-control test, each subject cycled immediately after 30 min of supine rest. During seated rest and exercise, one arm was supported at heart level (Horizontal), the other was in a position typically used in cycling (Pendent). A multifactorial ANOVA was performed to identify any interaction between the independent variables on ΔPV. There was no interaction between the test protocol and the arm position (F _1,9 = 0.005, P = 0.947, η _p ² = 0.001) on ΔPV from supine rest through exercise. Mean ΔPV was -12.2 ± 6.5, -13.6 ± 6.7, -10.7 ± 6.8, and -12.3 ± 4.2 % for the control Horizontal, control Pendent, non-control Horizontal, and non-control Pendent arm, respectively. There was no main effect of test protocol (F _1,9 = 0.738, P = 0.413, η _p ² = 0.076) or arm position (F _1,9 = 1.692, P = 0.226, η _p ² = 0.158) on ΔPV from supine rest through exercise. Mean ΔPV was -12.9 ± 6.4 and -11.5 ± 5.5 % for the control versus noncontrol test, and -11.4 ± 6.5 and -13.0 ± 5.5 % for the Horizontal and Pendent arm position, respectively. Thus, neither the postural control period nor the arm position affected ΔPV.