Systems and methods to determine a risk factor related to dehydration and thermal stress of a subject

A method to determine a risk factor related to dehydration and thermal stress of a subject, the method comprising:

• generating output signals, by a sensor group of sensors worn on a body of a subject, conveying information related to one or more of:
• location of the subject, motion of the subject, temperature of the subject, cardiovascular parameters of the subject;
• storing, in electronic storage, the information related to the subject;
• obtaining, using one or more processors, the output signals;
• determining in an ongoing manner, using the one or more processors, from the output signals, values of a water loss metric that quantify an estimated percentage of bodyweight of the subject lost in water;
• obtaining heat index information, using the one or more processors, for a contextual environment surrounding the subject;
• determining in an ongoing manner, using the one or more processors, from the output signals, values of an exertion metric that quantifies exertion of the subject due to work, wherein the exertion metric is separate and discrete from the water loss metric;
• and
• determining in an ongoing manner, using the one or more processors, individual values for an aggregated risk factor of the subject that indicates risk of thermal stress and dehydration of the subject at a given point in time, wherein the values of the aggregated risk factor are determined by aggregating values of the water loss metric, the heat index information, and the exertion metric for the subject.