Photo by Michael Rauschendorfer


Most of us have been there. You’re in the middle of a race and feeling great. Suddenly, and seemingly without notice, you hit the wall. You go from hero to zero in seconds. If the source of your bonk is a nutrition deficit, you can usually recover with time and patience. You slow down, relax, take in some calories, drink plenty of fluid and continue once the veil of darkness has lifted.

If your bonk is an electrolyte and hydration shortage, however, you may be in more serious trouble. Meredith Terranova, a Registered Dietician in Austin, Texas, cautions: “If you are severely dehydrated and lacking electrolytes, you may suffer extreme consequences including heat-related issues, seizures and even kidney failure.” She refers to a severe hydration and electrolyte deficit as “the showstopper” since it can quickly put an end to your race.

We’re in the thick of summer racing and training, and if you still have a race coming up (Ironman Louisville, for example) hopefully you’ve been practicing your hydration plan. This includes knowing your sweat ratio and how much water and electrolytes you should be consuming on an hourly basis in extreme temperatures. Below are a few tips for racing in the heat in order to avoid the cramping, bloating, elevated heart rate and other signs of dehydration that can not only slow you down, but blow your race.

1. Do a Sweat Test

Weigh yourself before a workout with minimal clothing and minimal fuel. Run for one to two hours. While doing this, drink from a 16-ounce bottle for ease of measurement and keep track of how much you consume. After your run, dry off and weigh yourself again with minimal clothing.

If you ran for one hour, drank 16 ounces of water and didn’t lose any weight, then your sweat rate is 16 ounces/hour. If you lost a pound, your sweat rate is 32 ounces/hour. While your sweat ratio will vary with training and temperature, it still gives you a solid baseline from which to determine how much you should be drinking per hour in an endurance event.

As a general rule, you should consume approximately 25-30 ounces of water per hour in hot and humid conditions. Electrolyte consumption can range from about 250-600 milligrams per 25-30 ounces of water. Again, these numbers vary from person to person and with each race condition, and should be practiced during training. If you are a light sweater, you may need less. Heavy sweaters may need over 1000mg of sodium during extreme conditions.

2. Always Have Plain Water

You may use liquid nutrition on the bike, but because of the concentration, you don’t necessarily need to consume an entire bottle each hour to properly hydrate. Therefore, you still need to supplement with a hydration source. Plus, if you find yourself dehydrated and thirsty, it’s good to know that you always have plain water with you in an emergency.


A selection of electrolyte products for training and racing

3. Use a Complete Source of Electrolytes

An electrolyte is any salt mineral that carries signals between cells allowing them to react properly. These signal carriers help regulate blood pressure, heart rate, water levels and muscle movement. If we don’t have enough electrolytes, our bodies won’t perform as well. The most common minerals are potassium, calcium, magnesium and sodium. Terranova suggests finding an electrolyte source with all of the above minerals, but much like reading labels at the grocery store, finding balanced electrolyte source can be tricky and may involve some mixing and matching. Popular brands of electrolytes include Endurolytes, Salt Stick, Thermolytes, and Nuun, but consult with your local triathlon store for assistance on determining which source is best for you.

4. Electrolyte Load Prior to the Event.

If you’ll be racing in hot and humid conditions, hydrate and increase your electrolyte intake a week prior to the event. Plain water will create a diuretic effect, so get and stay hydrated, being careful not to over-hydrate. Terrnanova suggests 80-100 ounces of non-caffeinated fluid at a maximum, mixed with electrolytes throughout the day. This is where products like Nuun tablets come in handy as you can conveniently drop them into plain water. During race week, you can also add a little more salt to your food and supplement sodium intake with tomato juice, chicken broth and other sources.

5. Know Your Aid Stations

Many Ironman races are using the new PowerBar Perform drink. Sample it prior to the race to see how your body reacts. While you may not have intentions of using what they provide, it’s always best to be on the safe side with a back-up plan. The same is true for the food and gels provided. Make sure your body can process them appropriately.

6. Acclimate

This is especially important if you are coming from a cold dry climate. Terranova suggests sitting in saunas, keeping the air conditioner turned off in the car, and training during the hotter times of the day. Some athletes practice hot yoga to simulate race conditions. If you practice heat acclimation, it’s also vital to practice proper hydration and electrolyte replacement as well. If you don’t hydrate properly for these acclimation workouts, your body will eventually pay for it in terms of fatigue, illness or lack of stamina during subsequent training sessions.  

7. Practice Your Race-Day Plan

As your heart rate increases, your body’s ability to absorb nutrients and hydration decreases. During a hot and humid race, your heart rate will be higher than normal. Know this going into the event and adjust your effort levels accordingly. You may have to slow down in order to ingest the proper ratio of nutrition, hydration, and electrolytes. This one tip can save your race. You simply cannot run as fast in 90 degree heat as you can in 45 degree weather. During extreme situations, you may also be tempted to skip nutrition breaks. Don’t. Your goal is to come off the bike with a full tank of gas, ready to run.

8. Keep Your Core Temperature Cool

With Ironman, the biking and running will be done in the heat of the day and, therefore, it is vital to keep your core temperature cool. Put ice in your caps and jersey, keep a bandana or sponges around your wrist or neck with cold water or ice, and carry your own water bottle so that you can drink frequently. You may also have to adjust your pacing strategy to keep your heart rate and breathing at a level that will allow you to absorb food and hydration.

9. Damage Control

If you do find yourself overheated or dehydrated during the race, first adjust your pace so that your body will be able to absorb the water and electrolytes. Also, begin cooling your core temperature with ice. If you are bloated and covered in salt, chances are you are not taking in enough water to absorb the electrolytes and nutrition. If your muscles start to cramp, take salt tablets and drink plenty of water until the cramps subside. In extreme cases of dehydration and electrolyte imbalance, seek medical attention immediately.

While race day always proves unpredictable, these tips go a long way to keep your body’s gas tank topped off so that you’ll be a showstopping success and not a victim of a showstopper like heat.


Carrie Barrett is a USAT Level 1 Certified Coach and freelance writer based in Austin, Texas. Her articles have appeared on, Runner Triathlete News, Inside Texas Running, and the recent triathlon anthology, The Meaning of Tri. Barrett is also a member of Erin Baker’s National Triathlon Team. For more information on her coaching, speaking and writing, visit