Hypohydration Does Not Alter Standing Balance

We examined the effect of body water deficits on standing balance and sought to determine if plasma hyperosmolality (P-osm) and/or volume reduction (%Delta V-plasma) exerted independent effects. Nine healthy volunteers completed three experimental trials which consisted of a euhydration (EUH) balance test, a water deficit session and a hypohydration (HYP) balance test. Hypohydration was achieved both by exercise-heat stress to 3% and 5% body mass loss (BML), and by a diuretic to 3% BML. Standing balance was assessed during quiet standing on a force platform with eyes open and closed. With eyes closed, hypohydration significantly decreased medial-lateral sway path and velocity by 13% (both p < .040). However, 95% confidence intervals for the mean difference between EUH and HYP were all within the coefficient of variation of EUH measures, indicating limited practical importance. Neither V-plasma loss nor P-osm increases were associated with changes in balance. We concluded that standing balance was not altered by hypohydration.