Bioelectrical Impedance Analysis and Self-ratings During Periods of Normal and Over Hydration

Abstract

The current recommendation for any professional voice user is to drink at least 64 oz of water per day, but the optimal amount is unknown and frequently more is recommended. Body response to fluid adjustment is not well defined. Bioelectrical impedance analysis (BIA) was used to measure body water changes of in young adults (15 males, 21 females) studying acting and communication sciences and disorders at a university. Half had habitually good hydration and half were poorly hydrated. A counter-balanced design was used for two 3-day periods of normal and over-hydration conditions, separated by 1 week. The time of the menstrual cycle was controlled for in one group of females. Participants drank 64 oz of water/day for normal hydration and 112 oz for over-hydration. BIA measurements of total body weight, total body water, and electrical impedance were collected during the first and third day of each hydration condition, and participants provided self-ratings of perceived hydration levels. Manipulating water intake did not change overall total body water levels. Results revealed no significant gains in total body water during the over-hydration condition, even among participants with poor baseline hydration. The homeostatic level may have been influenced by habitual hydration and require more time to change. Participants were inaccurate in their self-assessments of body water levels.