Heat Training Hydration Protocols

by Terrence Mahon

Editor’s note: Our team has learned a lot of tricks to make heat training more comfortable. A big one involves not getting too dehydrated during the heat session. One way to avoid this is by hyperhydrating before you start. This is a strategy long known to elite runners, so we asked world-class running coach Terrence Mahon to explain how to do it.

There may be a fine line between heat training that leads to adaptation and heat training that leads to exhaustion. Knowing the difference will help you to maximize your heat adaptation without leaving you feeling fatigued and depleted leading into future training sessions. However, we sometimes forget both hydration and electrolytes when plotting out heat training. If your heat training protocol isn’t accounting for this important piece of the puzzle then you may be at risk of going too deep into the red zone.

Hyperhydration for heat training

Hyperhydration is taking a greater-than-needed-amount of fluids prior to exercise so that you start your workout with a tank that is beyond full. Most athletes, especially runners, find it nearly impossible to consume enough fluids to offset what they lose in a heat session. By taking in more fluids prior to your workout, you can push back when dehydration starts to impact performance. In this manner you would consume water along with sodium (or an electrolyte mix) with an option to add in a small amount of carbohydrates for taste. It is important to not hyperhydrate with just water alone as this can cause hyponatremia – which is a very dangerous condition.

The trick with hyper-hydration is figuring out how much fluids you can intake relative to your needs that will aid in your long-term hydration status without leaving you so bloated that it makes you feel lethargic or affects your performance. It all comes down to timing and practice.

*Note that the following protocols are merely suggestions and there will be a lot of testing and retesting that should be done to fine tune these plans to fit your individual needs. 

Pre heat training hydration:

1. Determine your sweat-loss rate while heat training (see below).
2. Fill a bottle with fluids that equals 50% of your sweat rate/ hour. This bottle will have water with some small amount of carbs and/or citric acid for taste. If you are engaging in a long heat training session at a moderate intensity then you can experiment with taking in a larger amount of fluid – up to 100% of your sweat rate/ hour.
3. Add in sodium or an electrolyte mix to the bottle. If you are a low to moderate salt sweater then experiment with adding in sodium in the ratio of 500–750mg per 32 oz (1 liter) of fluids. If you are a heavy salt sweater than you can up that ratio to 1000–1200mg per 32oz (1 liter) of fluids. ¼ tsp of table salt contains ~600 mg sodium, 1 gram of table salt contains ~400 mg of sodium.
4. Assuming you are already adequately hydrated, begin your hyperhydration fluid intake approximately 90min to 2 hours before your session and finish it about 30 minutes before you start.
5. Give yourself time to use the bathroom to free up your bladder prior to starting the heat session.

Hydration during heat training

1. If running for your heat training session, then fill a bottle with fluids that equals 50% of your sweat loss rate/ hour. This bottle will have water and the normal amount of carbs that you would use when doing a moderate or high intensity training session. If you are cycling, cross training, or engaging in a long heat training session at a moderate intensity then you can experiment with taking in a larger amount of fluid – up to 100% of your sweat rate/ hour.
2. Add in approximately 25–50% of your estimated sodium loss to the fluid mixture. Err on the lower end range if not a heavy salt sweater and the higher end of the sodium intake range if you are. Adding 1 tsp–1 tbs (4–20 grams) of citric acid can improve the taste.
3. Drink 4–6 oz (125–175ml) of fluid every 15–20 minutes of exercise during your heat training. Heavy sweaters can aim to drink a bit more and light sweaters can aim for a bit less. You will need to experiment with this as you don’t want to upset your stomach while drinking and training.

Post Heat Training Hydration

1. Add up how much fluid you took in both before and during your heat training session.
2. Calculate the difference between your sweat rate per hour and how much you consumed.
3. Aim to drink another 50% of your total sweat loss in fluids of the same solution content as used during the training session.
4. The goal of your post hydration plan is to not just hit a net neutral hydration status to account for all the fluid loss during exercise, but to also account for the fluid loss post exercise during the cooling down phase. Even if you are no longer training your core temperature will continue to be elevated and as such you will be losing water as your body works to return your core temperature to normal.
5. Over the next few hours continue to drink fluids at a normal rate to insure a proper recovery and allow you to start your next training session fully hydrated.

Final Reminders

1. Consult a doctor, registered nutritionist or dietician before adding excessive amounts of sodium to your diet if you have high blood pressure. 
2. Signs of dizziness, fatigue, lack of concentration or faintness can be signs of either hyponatremia or an overload of electrolytes in the bloodstream. Please consult a physician if you have any questions or concerns in this area or have experienced these symptoms in the past. 
3. Monitor your Heat Stress Index while engaging in heat training. Avoid going into the red zone by reducing your intensity, removing clothing, and maintaining proper hydration.
4. Give yourself time to adapt to both the hyperhydration and during hydration fluid volumes. Most athletes cannot tolerate high volumes of fluid intake right from the start, but with practice they are able to increase it considerably.

Determining sweat rates and sodium loss

Each athlete is unique when it comes to how much water and sodium they lose when training at various intensities and in various climates. Sorting out your individual needs can be a performance game changer whether it be with your next training sessions or the major competitions down the road. It is nice to know that whatever climate conditions get thrown at you on the day you will be ready to handle it.

Hydration

Determine if you are a heavy or moderate sweater when training/ racing in the heat.

1. Weigh yourself naked before you do a moderate intensity training session in typical climate conditions.
2. Complete your training and note how many oz (ml) of fluid you took in while training.
3. Towel off and weigh yourself again while naked.
4. Calculate the difference between your pre & post weight.
5. Convert how much you drank during training to weight and subtract that from the total above. 1 kg weight loss equals 1 liter of sweat lost. 1 pound of weight loss equals 16 ounces of sweat loss.
6. Calculate your dehydration rate per hour of training. For example, if you lost 1lb (.45kg) in a 30-minute training session then you would be at a sweat rate of 32 ounces (0.9 liters) per hour during normal training.
7. Repeat steps 1–7 above when doing a heat training session. Compare the results and determine how much more water you lose when doing the heat training session at a similar intensity.

Sweat rate can vary among athletes from very little fluid loss to over 135 ounces (4 liters) per hour. Knowing your numbers when in both cool and hot conditions can help you avoid dehydration by dialing in your pre-, during- and post-fluid intake. A sweat loss deficit of greater than 2% of body weight will increase heart rate and core temperature while also decreasing muscle power and affecting overall performance.

Sodium/ Electrolytes

Determine if you lose a lot of salt (sodium) when training/ racing in the heat.

1. Do you get salt marks on your skin or training/ racing apparel?
2. Does your sweat taste salty?
3. Does your sweat sting your eyes?
4. Do you feel faint or dizzy after training in the heat or after long/ hard sessions?
5. Do you often get muscle cramps during or after training in the heat or long sessions?
6. Do you have an insatiable desire to eat salty foods after you train?
7. Do you often feel much worse after training/ competing in hot conditions than on moderate temperature days?

If you answered yes to 3 or more of the above then you likely lose a lot of salt when you train. Multiple studies have shown that the average athlete loses just under 1000mg of sodium per 32oz (1 liter) of sweat loss. Salty sweaters could lose up to 2x this amount and others may lose much less. It depends a lot on the intensity and duration of the training session or race, what the weather is like when you are exercising, and how heat adapted you are. There are other genetic factors as well, but that is beyond the scope of this article. Any way you slice it, you may want to consider adding in some sodium into your next hydration plan, especially when heat training or when competing in adverse conditions.

About the Author – Terrence Mahon

Terrence Mahon is internationally recognized as one of the great minds in coaching. Having coached Olympians like Deena Kastor and Ryan Hall, he has stayed at the forefront of performance by bringing the latest innovations in thermoregulation to his runners.