I can’t count how many times I hear that someone has had a good workout since they “worked up a good sweat”. Well, we can sweat in a hot tub or sauna too! Sweat does not equal a workout – good or otherwise.
Sweat is a response to increased body heat. Sweat is produced to then cover the skin surface and subsequently be evaporated. In the evaporation process, cooling takes place. Levels of humidity as well as a slight breeze can greatly affect the rate of evaporation. The goal of sweat is to cool the body. Once body temperatures reach 106, cell damage is taking place; not a good thing.
Often, we are fooled by the fact that down here in the southwest it appears that we aren’t sweating as much as in other parts of the country. Well, that happens to be completely untrue. In fact a recent survey found that “the average Phoenix resident produced 26 ounces (0.77 liter) of sweat per hour during a typical summer day last year.” This Procter & Gamble Co. survey studied 100 cities to determine estimates of the amount of sweat a person of average weight and height would produce walking around for an hour in the average high temperatures of a particular city during June, July and August. Phoenix ended up #1 on the sweatiest cities list for 2006. We sweat more than Miami! The main difference is that due to our dry atmospheric conditions (10-22% humidity) it evaporates faster on us than it will in a place like Miami where it drips off you in 70% humidity!
Now a really bad situation is when in fact you actually stop sweating. You are on the verge of heat related conditions that can culminate in heat stroke, coma and death. Actually stopping sweating is a medical emergency! So, be careful of course, but don’t be fooled that because your skin is not dripping wet that you aren’t sweating.
The amount of sweat lost during exertion is very individual. Even the chemical make up of the sweat differs from person to person. Perhaps you have notice how after some runs you see runners covered in “salt” residue and others not. That is one of the reasons each of us need to experiment with fluid replacement strategies before race situations. But, do not jump to the conclusion that you have somehow lost more electrolytes than someone else and arbitrarily start adding them to your drinks or diet!
Since sweat loss is individual, here’s how to determine the amount of sweat you lose in a given condition. Weigh yourself naked. (Don’t worry, nobody will look.) Go for a one-hour run. A shorter run could be used but this is what is most often used. Do not take fluids during the run. Then, once again after the run and before you take in any fluids, weigh yourself naked (We’re still not looking). Take the difference in weight and divide those pounds by 2.1. That will give you the number of quarts of fluids you need to replace. So, a body weight loss of six pounds is just less than three quarts (6/2.1=2.85) of fluid loss. (1 kilogram equals 1 liter of fluid for the metric minded.) And here is the importance of this assessment: performance is impacted with as little as a 3% loss of fluids and a 5% body weight loss will equal about a 10% decrease in performance. That is only 4.5-7.5 pounds in a 150 pound runner.
You then need to add that amount of fluid to your recommended daily amount of intake. The rule of thumb is nine eight-ounce glasses for women and 13 eight-ounce glasses of fluids for men.
By the way, those figures above aren’t unusual weight losses at all. And for dieters, that may seem like a good thing. It isn’t. You’ll gain it all back once you re-hydrate. And, if you do not re-hydrate appropriately and completely, you will workout less (less frequency, shorter duration and less intensity), which means you will lose less real weight over time not more. So, never be fooled that sweating and not replacing fluids helps you with weight issues. So stop running around in the heat with warm-ups on!
As another little acknowledged point, well acclimated athletes sweat earlier than those not acclimated. Yes. You sweat earlier because your body “knows” it needs to be cooled earlier and gets it going! Unfit, non-heat acclimated individuals have a slightly delayed sweat response. Therefore, their body temperatures rise faster and they suffer more.
And finally, here are ways to improve your ability to cope with warm conditions. This means that you’re body will sweat earlier to prevent your body temperatures from skyrocketing.
– Train in the heat several times a week
– Train in the heat of day the week before a race
– Stay hydrated all week long
– Improve running economy
– Increase intensity of training
– And know that endurance running does not acclimate you to heat as efficiently or effectively as shorter quality runs.
So, just like heart rate, sweat rates just do not correlate to effort well. Drink up and workout, weather (yes that’s a pun) you get sweaty or not!