Time Onset Sweat Sodium (TOSS) Study

Prior to each trial, you will be provided with urine jugs and food/fluid logs to record food and drink intake for 24hr. You will be asked to log food/fluid intake 24hr leading into trials. We ask that you match your diet for both trials, as much as possible. Also, we ask that you match caffeine consumption prior to trials. Lastly, we ask that you refrain from strenuous exercise and alcohol consumption for at least 12hrs leading into trials. Either of these exclude your participation in the study for safety reasons. You will be asked to provide a small urine sample upon arrival to the lab before trials. The purpose of this is to verify hydration prior to exercise in the heat. If you are not hydrated upon arrival, you will be provided and asked to drink 16oz (a bottle) of water prior to the trial. Just prior to, and following each long trial, you will be asked to provide a small saliva sample. To do this, you will be asked to actively produce saliva and guide it into a small container. This process takes \<5min. Next, you will have your nude body mass measured and you will be instrumented with a labbased sweat collection patch (large band-aid on the forearm), and the Hdrop sweat detection device on your left upper arm. The Hdrop will be synced with electronic applications (phone apps) to assure data collection. You will then self-insert a rectal thermistor \~15 cm past the anal sphincter to monitor core temperature throughout exercise (for safety purposes). You will also be fitted with a heart rate strap that goes around your chest. You will then be asked to enter the environmental chamber and exercise for 30min. This will serve as the short exercise trial aiming to assure comfort with the 120min exercise trials. Data will be collected during the short trial and comparisons will be made for the longer, 120min trials. The environmental chamber will maintain a consistent temperature (80-100 degrees F) and humidity (40 to 60 % relative humidity). You will be monitored fo