Guess How Much Weight I Lost
PrintTemperatures are climbing! Yesterday the high in the Midwest was well over 100 degrees. More out of curiosity than anything I took my sweat rate from my easy morning run on the trails.
I jumped on the scale nearly nude before heading out the door for my run. I stuck to the cooler trails for most of the run and stopped twice for fluids over the hour and ten minutes. In total I drank about 16-17 ounces from the park water fountains. I know this because I counted my swallows based on how I know a fluid ounce feels in my mouth. By the end of my run the temperature was pushing the mid 80′s with reasonable humidity. When I returned home I fought off the urge to bloat myself with guzzled fluids. Instead I headed straight to the scale for another weigh-in. I stripped off my sweaty clothes to weigh myself nearly nude once again.
I subtracted my nearly nude pre-run weight from my post-run weight. This came to 3 pounds in just over an hour of running! I didn’t even run in the peak heat of this very hot day. I then took the 3 pound loss and multiplied it by 16, as in 16 ounces of fluid. This translates to 48 ounces. I then add the fluids I consumed on the run. If I add the 48 ounces to the 16 ounces I drank this translates to a sweat rate of 54.8 ounces per hour for the 1:10 run in about 85 degree weather and running an easy effort. This number would easily increase had I been running at a harder effort or at a hotter point in the day.
I didn’t really need to do all of the calculations. My clothes were clearly drenched with sweat and it’s hot outside, right? Not to mention, there is no way for me to keep up with a sweat rate of nearly 55 ounces per hour, not that I would try to match this sweat rate anyway. This is a nice example of how dehydration is inevitable because my sweat loss exceeds the rate at which I can absorb fluids.
We have to understand as athletes to train with caution during this very warm weather running.
7 Comments
Thanks for the reminder on calculating sweat rate. It sounds like you had a hot run! Would it have been more accurate to weigh in your workout clothes before and after the run? This would account for any sweat absorbed by your workout clothes. I guess if you’re wearing dry wicking, technical fabric it might not make much of a difference. Just wondering…
Today was much worse humidity wise. I didn’t weigh, but I’m sure I lost much more! Great question – It’s actually more accurate to weigh nearly nude/without clothes. If you weighed with clothes on you would still be carrying fluid weight; this would not reflect how much you sweat according to the scale because you are still carrying your sweat. Without clothes is a more clear picture of total fluid loss.
Thanks for the tip! David and I are in South Bend, IN this weekend for David’s nephew’s wedding so we’re not too far from you! It was very humid when we flew in to Chicago on Thursday evening.
Oh, I see what you’re saying…I don’t know why I didn’t realize that in the beginning!
You ARE so close! Have a wonderful trip and time at the wedding!
What % of sweat rate loss should an athlete strive to match? In other words, if an athlete loses 50 fl oz of sweat per hour, should he aim to replace 60% (i.e. consume 30 fl oz per hour during exercise)?
Crystal, I will shoot you an email on this.