This is a question that many endurance athletes should know, but they generally don’t. As athletes, we are always looking to gain more watts on the bike, run faster miles, swim more yards/meters. However, we often neglect the facts that our body can only operate as trained if its being replenished correctly. When it comes down to sweat, we need to know how much fluid we are losing and how many electrolytes so we can properly hydrate and keep the body functioning at a high level. I hope this blog will open your mind to finding your own sweat rate and making better decisions on how to best manage racing or training in heat.
Why is a Sweat Test Important?
Depending on the literature you read, performance can start to suffer with up to 2% loss in body weight during exercise. For athletes that are training or racing for long periods of time, this can lead to high fluctuations in weigh due to fluid loss that could be hurting your performance. With the average athlete losing somewhere between 1-2.5 bottles (20-50 oz) of fluids per hour, its critical that we have a plan in place to replace this fluid to keep your body operating as planned. By knowing how much you sweat, you can start to develop the ideal plan for your performance and safety.
Risk of Not Knowing Your Sweat Rate
For those that are guessing, you are opening yourself up to possibilities of dehydration or hyponatremia. Both are dangerous and should be understood before performing any long duration activities. Dehydration is the lack of water in your body and can cause massive performance loss and possible death in extreme circumstances. Hyponatremia is the over abundance of water compared to sodium (salt) in your body which can cause massive performance loss and possible death as well. When in long distance/duration events, your body is in a constant flux of liquid and electrolytes that it needs. You are a moving chemistry lab that needs the right mixture to keep operating at its desired rate. By not knowing what your chemistry lab looks like, you are taking a shot in the dark and risking decreased performance or possible harm to your body. For all the hours that you have put into training, your day can be stopped quickly by dizziness, vomiting, nausea, lack of performance, etc, due to not knowing your sweat rate. This is one of the key pillars to any athletes performance.
One of the best articles I’ve read that is in context to triathlon can be found at slowtwitch.com (www.slowtwitch.com/Training/General_Physiology/The_Math_of_salt_loss_1093.html). This artlcle takes an in-depth look at salt loss and how it factors into performance. While salt supplementation may not be required for any activity 3 hours or less, as you start to go up in duration, its important that you keep your moving chemistry lab (body) in check. This will be different for everyone, but its important that you have the education in place to know what your body needs. Don’t take this information as a one size fits all. Whats important to know with this topic is that its different for everyone based on how their body operates in different settings.
Performing a Sweat Test
In order to check your own sweat rate, weigh yourself prior to your training for the day. Train at your desired intensity for 1 hour and then re-weigh yourself. Make note of any food or water you’ve taken in or if you’ve used the restroom. If you have taken in any water during that hour, note how much and factor that into your ending weight. Your sweat rate will be your starting weight minus your ending weight. If you took in any food or water, subtract that from your total.
starting workout at 180 lbs
ended workout at 177.5 lbs
- No water or food taken in for 1 hour moderate activity
- weight lost: 2.5 lbs
- 16 oz = 1lb
- 40 oz lost/hour
Things to make note of during your test are
#2 Weather Conditions
#3 Sweat Rate
As you go throughout the year, it would be wise to find your sweat rate in different conditions. Based on how your body responds to different environments, it will guide you in how to best replenish your fluids and electrolytes as needed. If you are using a sweat test from 65 degree weather and racing in 85 degree weather, you may suffer in performance due to imbalances.
We train all year for big events, and then go into them without a dialed in hydration plan. While many individuals focus on nutrition and getting in the calories they need, they forget about hydration and knowing exactly what they need in the race day environment (wind/humidity/temperature/intensity). This test can be done in 1 hour and is important for every athlete to know and understand. Your body is the most important part to you having a great performance. Without a dialed in hydration strategy, you are simply taking a shot in the dark at a strong performance.
Disclaimer: I am not a registered dietician and do not intend for any athletes to use this information without consulting with a dietician or doctor. The purpose of this article is to educate athletes on a general level, but not to prescribe any specifics to any individual. It is up to each athlete to consult with professionals as needed to develop their own strategies for dealing with sweat rate.
www.slowtwitch.com, ” The Math of salt loss”, Toker (2009)