Towards the measurement of sweat rate via wearable sensors

The sweat rate is the flow of water vapour emitted by the skin, i.e. the amount of water emitted per unit area during a defined period of time. Its measurement is challenging due to the low flow of water involved, literature reports for adults whole body averages ranging from 0.2 g/m2 min in mild climate conditions to 40 g/m2 min in extreme conditions. A number of pathologies (hyperhidrosis, anhidrosis, diabetes, hyperthyroidism etc) as well as physiological conditions (stress, physical effort, menopause etc) may result in increased or decreased sweat rates, but the indirect calculation of a whole body average value from the weight loss is the only reference method. Being able to continuously measure this parameter may find important applications in medicine and in sports, but a wearable system would be needed for this purpose.