Supplementary information files for "At least 10 minutes of seated rest is required for stabilisation of blood-based hydration biomarkers"

At 0 and 5 min, blood (0 min: -3.3%; P < 0.001; 5 min: -1.2%; P = 0.034) and plasma (0 min: -5.9%; P < 0.001; 5 min: -1.7%; P = 0.035) volume were lower than 40 min values. Conversely, plasma osmolality was higher at 0 min (+ 0.61%; P = 0.005) and 5 min (+ 0.55%; P = 0.007), whilst blood/plasma volume and plasma osmolality were not different from 10 min onwards. Plasma sodium, potassium and chloride concentrations were not different from 40 min throughout the sitting period ( P ≥ 0.056).

These data demonstrate that blood/plasma volume, as well as plasma osmolality were affected by posture and/or walking, but all are not significantly different from 40 min within 10 min of seated rest. Therefore, studies involving blood-based hydration measures taken in an upright seated position should allow at least 10 min of postural control prior to sampling.<br><br>© The Author(s), CC BY 4.0</p>