The Mechanisms of Sweating
Most of us sweat on a hot day just working around the house or taking a walk. And most of us sweat during fitness class — some more than others. In hot weather, we may sweat even more. It's not uncommon for participants in a fitness class to make it clear that they either want a fan on them, or they do not want a fan on them. As the instructor, it's difficult to make sure that everyone is satisfied with the situation.
Let's begin with an obvious discussion — here's what you need to know about sweating:
- Sweating is a natural process and a vital tool for good health.
- An increase in body temperature will cause us to sweat — the body loses heat when sweat evaporates from the skin, thus allowing our bodies to retain a safe temperature while exercising.
- During physical activity, sweating is the most effective way for the body to get rid of heat and maintain a safe internal temperature.
- The amount people sweat varies a great deal — everyone is different.
- As physical fitness improves, sweat loss increases..
- Sweat is over 99% water, but it also contains minerals, amino acids, and metabolites. However, the most common mineral is sodium — that’s why sweat tastes salty.
- The risk of heat illness is greater in unfit, unacclimated people, partly because their bodies heat up more before sweating begins. If you stop sweating, you may be headed for heat exhaustion or heat stroke (the more serious of the two). See also Heat Injuries: Learn to Recognize the Signs.
- There are medical conditions and medications that will affect your perspiration rate. If you are finding that you are suddenly sweating more, or less, or if you are uncomfortable with the volume of sweat that you produce, then you may wish to seek medical advice.
The Benefits of Sweating
There are many benefits to sweating, but here are four very important ones:
- Sweat is your body’s natural way of providing a high-tech cooling system: it’s a good thing!
- On a small scale it can burn calories in conjunction with traditional training. Sweating is a form of exercise, as the actual sweating process takes energy (around 300 calories per hour for a typical sweat). Therefore, sweating can help with weight loss and will increase metabolic rate.
- It's believed that sweat will improve circulation and boost the body’s immune system.
- Exercise associated with sweat releases endorphins into the body, making you feel less stressed.
You Should Avoid overheating
There is a big difference between a healthy sweat and a body that's overheated.
- Training and sweating until the body overheats is extremely dangerous.
- If your body reaches too high a temperature you can experience cramping, nausea and lose consciousness.
- If you STOP sweating, you may be overheating and heading for heat stroke, a very serious condition.
See also: Heat Injuries: Learn to Recognize the Signs
So remember these three simple rules about exercising in hot weather:
- Wear light, comfortable clothing.
- Always have a bottle of water for hydration. 2
- Let sweat regulate your body's temperature, but if you get overheated, stop exercising, drink water, and rest for a time.
Do fans really cool you down?
The fan controversy comes up every year, particularly in the summer, of course, and so it's time once again to remind everyone of how much we need to respect each other's needs in the fitness class. 3
No one knows for sure if fans are an effective way to cool you down while exercising or during a heat wave.
Research has been done, but unfortunately has proven little. Here are some points from an article from Health Day News, Thursday, July 12, 2012, discussing the results of a meta-study from The Chochrane Library of July 11th where researchers looked at all the research about fans and their usefulness that they could find:
- There's no reliable evidence to show whether electric fans keep people cool during extreme heat waves.
- While some of the studies suggested that indoor fans might reduce heat-related health problems, others suggested that fans might actually make things worse.
- "A fan might help to increase heat loss if the temperature is below [35 degrees Celsius] and the fan is not directly aimed at the person, but when temperatures are above , the fan might actually contribute to heat gain." [My italics]
- "The evidence is not already out there on the benefits and harms of electric fans. We need [a large research study] to resolve this long-standing and on-going uncertainty, and to help people make well-informed choices about their use."
- "It is important to know about the potential benefits and harms of electric fans when choosing whether to use one. This is true if you are simply making a decision about your own use of a fan, but it also applies to broader public health decisions, such as whether to give electric fans to groups of people during a heat wave.”
This comes from an article "Why Fans Don't Always Make Things Cooler" in Wired dated August 20, 2015:
"There is one other key ingredient for a fan to do its job — liquid water. This is all about evaporation. When liquid water turns into gas water (water vapor), this takes energy and the energy comes from the rest of the liquid water. The result is that the remaining liquid water gets colder. Evaporation cools off water. Here is a more complete explanation from a previous post on evaporation.
"For humans, we call this liquid water “sweat”. Fans need sweat to cool off a human. When air moves quickly over liquid water, it increases the evaporation rate. More evaporation means cooler liquid sweat and a cooler human."
So what about fans in fitness class?
What’s a fitness instructor to do? Personally, I dislike the fans in fitness class. I prefer to cool my body with natural sweat. I find the fans too loud — and since I do not use a mike, I have to raise my voice more than usual. People have complained, as well, that they can't hear the music when the fans are on. But I have no desire to turn up the music as that isn't good for us either. (See Music and Fitness Class: The Good, the Bad, and the Ugly) As well, for me, the fans irritate my allergies by spreading pollen and dust throughout the room. Indeed, just the air blowing in my face will irritate my eyes.
Two facts we can all agree on are:
- Sweat is good. You should hydrate often.
- Overheating is bad. If you get too warm, stop exercising, drink water, take a break.
This is clearly a subjective decision. If you feel hot, you want to find a way to cool down. If you find the fans noisy or too cool on your skin, you want the fans off or, at minimum, turned away from you. Compromise is the only way for everyone to enjoy fitness class on a warm day:
- Research doesn't give us a definitive answer as to the cooling value of a fan, but we do know that if you are not sweating, the fan will most likely not help.
- Respect the boundaries of those who want a fan as well as those who don't.
FOR THOSE WHO DON'T WANT A FAN NEAR THEM:
- Try to move to another spot in the room.
- Ask that the fan be re-directed away from you or up towards the ceiling.
FOR THOSE WHO WANT TO USE A FAN:
- Arrive early and determine where the fans are in the room.
- Move a fan closer to you if you know you will want it.
- Talk to the instructor about your requirements, but remember that compromises will probably have to be made.
- Respect those who do not want a fan directly on them by making sure it is not pointing at them.
- Aim the fan (1) at yourself, (2) towards others who have told you that they don’t mind it, or (3) upwards to the ceiling.
- Please turn off the fan as soon as you feel that you have cooled down.
- Please use the fans only during the cardio portion of the class.
- Please do NOT use the large fan (usually at the back of the room); it is much too loud (covers up my voice and the music) and moves too much air.
I am a BCRPA-certified fitness instructor in Vancouver, BC. I teach four classes at the West End Community Centre in Vancouver, BC, mostly designed for the older adult. The Inevitable Disclaimer: Everything published here expresses only my opinion, based on my training and research. What you do with the information is entirely your own responsibility. I am not liable for any injury you suffer that seems to be related to anything you read here. Always consult your doctor before beginning an exercise program. For other articles, return to the table of contents.
Source for this section: A web page by Dr. Bob Murray, Ph.D. ↩︎
Please bring your water bottle to class every single time — and use it whenever you have a moment. Even if you don't feel thirsty, your body needs hydration — especially if you're sweating. ↩︎
As the instructor, I also want things to be safe. I am concerned about heat and cold, noise, too much breeze, and someone overheating. ↩︎