Real-time microwearable sensor for monitoring human hydration status

Fluid restriction followed by exercise-induced dehydration The first visit (less than one hour) will involve several measures of hydration status (including body weight, a small quantity of blood collected via venipuncture in the arm and urine samples). You will then go about your normal daily activities for the next 24 hours but will be requested to minimise fluid intake. The following dietitian guided information will be provided: In the 24 hours leading up to your exercise session, please minimise: - drinks & liquids e.g. water, coffee, tea, soft drink, sports drinks, milk, juice, alcohol - fluids that are part of a food e.g. soup, sauces, gravies, pudding, yoghurt, salad dressing - foods that will melt down to a liquid e.g. ice cream, frozen yoghurt, milkshakes/smoothies, ice blocks, ice cubes - juicy fruits or vegetables e.g. melons (watermelon, rockmelon,honeydew, etc.), berries (strawberries, blueberries, raspberries, blackberries, etc.), tomatoes, cucumbers To reduce thirst and alleviate dry mouth: - eat a low salt diet (salty foods will increase your thirst) - keep hard candies, mints and gum available. some people find sugar-freevarieties to be more thirst quenching - brush your teeth - chill mouthwash and gargle for a fresh feeling - rinse your mouth with water (no swallowing). - add lemon or cucumber to your water to help quench your thirst. - freeze or partially freeze pieces of fruit for a refreshing treat: like lemon wedges, orange sections, peaches, berries, or grapes - breathe through your nose and not your mouth - avoid mid-day heat The second and final visit (24 hours following the first) will involve exposure to a hot and dry environment (40 deg C and 20% relative humidity). You will walk at 5 km.h-1 and 1% gradient for 150 minutes. This will be conducted in five 30 minutes bouts, separated by 20 minutes rest. Before, during, and after this session several measures of hydration status (including changes in body weight, blood and urine samples) will be recorded during the rest periods. Nude body weight will be conducted alone in a lockable room. Blood samples (six by 6-ml collections) will be collected from a cannula inserted, by a trained phlebotomist, into the antecubital fossa of the elbow. The blood will be assessed for osmolality, a hydration marker, at each time point. Baseline urine samples will be assessed for specific gravity and colour. Heart rate, core and skin temperature will be recorded continuously. Heart rate will be measured with a chest strap and watch, core temperature via a rectal probe and skin temperature with four wireless sensors (approximately 1cm in diameter) placed on the surface of the skin. This session will be overseen by an exercise scientist and/or exercise physiologist accredited with Exercise and Sport Science Australia (ESSA). The hydration MicrowearableTM sensor will also be worn continuously throughout this second visit. The MicrowearableTM is a disposable single-use device, developed by WearOptimo, it comprises an array of microelectrode-projections that upon application to skin, will penetrate the upper most layer of the skin. The sensor may be placed on the following locations: shoulder, sternum, and hand. Bioimpedance spectroscopy (BIS), which has been developed as a measure of body composition and fluid volume status, is used to continuously measure skin tissue composition between the microelectrode-projections. The washout period prior to undertaking the alternative condition will be at least 7 days.