How To Prepare For And Manage High Temperatures


by Jimmy Dean Freeman 

We are on the cusp of summer and some of the hottest ultra races are coming up fast. Last year both the San Diego 100 and Western States 100 saw brutally high heat, which led to a record low 47% finishing rate at San Diego and presented some major physical carnage at Western States. I am going to review heat preparation and management strategies in this article, but the bottom line is you should try many things to determine what works best for you. You also need to know the red flag symptoms to avoid some disastrous consequences. Heat management skills are crucial for the success and safety of all endurance athletes.

Before we dig into this, please understand that these are my personal insights on heat running and are by no means a definitive set of guidelines. I am not an expert, nor a scientific authority. While I’ve had some success in hot weather races, I’ve also made some major mistakes and seen the dark side of hot weather racing. When the stomach goes south due to heat stress, it feels nearly as bad as having food poisoning and even worse, it almost inevitably leads to a dreaded DNF.

Part One – Heat Preparation

So you signed up for a race that is known for high temps and/or humidity? How do you get the body ready to perform, especially if you are coming from an area that isn’t traditionally hot or you are training through the winter for a spring/summer race? That’s a tough one, because the best way to heat train is to train in the heat.

Jamil Coury (Race Director of the Javelina 100 and numerous other hot races) has a lot of firsthand experience with hot weather. Living in the Phoenix/Scottsdale area of Arizona, he has ample opportunity to walk out his front door and experience 110+ degree temps. His routine includes a two-hour, 30-min acclimation run (in 100+ degrees) where he’ll carry four water bottles. He’ll try to drink about as much as he perspires (which is a lot) and use some of the water to pour on himself to assist in cooling his core temperature. Although I don’t think it accurately mimics true heat, many successful ultrarunners in less hot climates heat train by running with excess clothing. But be prepared for funny looks as you head out in 60 or 70 degree weather covered head to toe in fleece, gloves and a wool hat.

If that doesn’t appeal to you, many athletes who prepare for the Badwater Ultramarathon (a Death Valley run in the hottest week of July) are familiar with the benefits of dry sauna heat acclimation training. Dr. Lisa Bliss (a former medical director of Badwater, and the female champion in 2007) recommends sitting in a 160-180 degree dry sauna (steam rooms are not as effective for this type of heat acclimation), and drinking plenty of water. Starting the sauna session well hydrated is key as you are aiming to train the body to sweat more, and also to stimulate hormones that enable us to release fewer electrolytes in our sweat. Start with a 15-20 minute session and add a few minutes to each session, ideally every other day. End the sauna session if you feel dizzy or faint, as passing out in a sauna would be very dangerous. Aim to get that session up over 30 minutes, eventually up to as many as 45-60 minutes per session, and complete your sauna training no later than 7-10 days prior to your (hot) race. The key with heat training is to dramatically increase the body’s ability to efficiently process fluids and utilize them for evaporative cooling (through sweat).

Dehydration color chart at Michigan Bluff, mile 55 of Western States 100. Photo: Jason Headley

Dehydration color chart at Michigan Bluff, mile 55 of Western States 100. Photo: Jason Healey

Part Two – Race Day External Heat Mangement

Whether you maintained ample heat acclimation training or not, managing the heat on race day is still something that can make or break your race. During the hottest races, many athletes use a cloth bandanna to wrap around their neck. Wrap two handfuls of ice in it and roll it to tie around your neck. Having ice against the back of the neck cools the blood and helps cool your core temps tremendously. Wear a white cap (as opposed to a visor) and put a handful of ice in it atop your head. As this ice melts it trickles down your head and neck to aid in the evaporative cooling effect. Having an extra water bottle with ice water, and utilizing that to keep your head, neck and upper back wet, are also effective ways to aid in cooling you off. During my hottest races, I’ve also been known to wear fleece Moeben arm sleeves, soaking them with ice water and placing ice cubes in the pockets. At Western States last year, I observed Nikki Kimball and Meghan Arboghast placing ice in every area they could – in shirts, in shorts, on top of their head, on the back of their necks and apparently even in their bras. Sorry guys, but maybe you could wear one expressly for this purpose? It is obvious that if we can use externally applied water and ice for evaporative cooling, instead of 100% our own perspiration, it is more efficient and easier on the body. Although the goal is to keep the upper body as wet as possible, it’s best to keep the lower body dry since wet shoes can lead to blisters and wet shorts can lead to chafing (recommendation: use Body Glide, Trail Toes or your favorite friction combatant liberally on these hotter days when you’ll be trying to stay wet).

Part Three – Race Day Fluid/ Electrolyte Management

A key to successful racing in the heat is maintaining proper fluid hydration and electrolyte levels. Most ultrarunners have their own electrolyte replacement strategy, but nearly ubiquitous at all ultras and a part of most successful ultrarunner’s heat management arsenal is S Caps for electrolyte replacement. Regarding hydration there’s a chasm of divide between what people do, and what some experts recommend. There’s a lot of contrasting, even conflicting information out there. So you’ll need to experiment to find the best solution for you. How much one should drink will widely vary based on your personal sweat rate, how heat acclimated you are and how hot the race you’re running is on that day. Generally, 20-22 ounces per hour is thrown out there as a guideline for normal temps. That number could be double, or even more, on a hot day. But here’s the catch, if you overhydrate, you can put yourself into one of the most lethal states an ultrarunner can find themselves in: hyponatremia. Hyponatremia is defined as abnormally low concentration of sodium ions in the blood. (Editor’s note – see Dr. Marty Hoffman’s article elsewhere in this issue of UltraRunning).

Overhydration can be brought on by heat stress to the body and the over production of the hormone AVP (arginine vasopressin), which helps control the body’s water balance. High levels of this hormone direct the kidneys to reabsorb more water and produce less urine. When fluid intake is adequate, generally less of this hormone is released. But this can be difficult to determine for a non-heat acclimated athlete in a hot race. A great indicator of this is weight gain/loss during the event. If you’re gaining weight, it could be a sign you are overhydrating (consuming more fluid than you need, or at least more fluid than you are able to process). If your weight is up over 1%, it’s recommended that you cease drinking (and probably slow down) until it comes back down to normal or below levels. Dr. Timothy Noakes recommends in his book Waterlogged drinking to one’s thirst and being careful to not overconsume electrolyte supplements, since having more sodium present in the system will make you thirsty, whether you are appropriately hydrated or overhydrated.

Symptoms and signals of extreme water imbalance are: dizziness, lightheadedness, feeling faint, nausea, disorientation, feeling extremely weak or a headache. If ANY of these occurs during heat acclimation training or while running a hot race, it’s a sign you need to stop running (or get out of the sauna) immediately and seek medical attention, including a weight check.

Weight loss in an ultra is expected, in a 100-mile race, up to 4-5% could be considered typical over the duration of the race. Yes, weight loss is normal, to a point, as depicted by urine colors in the adjacent photo. Being severely dehydrated on top of sustained high running intensity on a hot day causes abnormal stress on the kidneys and could have you peeing Guinness colored urine (there is some medical speculation that taking NSAIDs in concert with this scenario might also contribute to this). If your urine becomes extremely dark, slow down the pace (or walk) and take in fluids. If your urine doesn’t get lighter in color and it stays coffee colored, or if you’re no longer able to urinate (and experience rapid weight gain), seek medical attention immediately. This could be a sign of renal injury (renal failure or Rhabdomyolysis), which could continue to develop after a race if the kidneys are clogged or shutting down, and while this is rare, it is something to be taken very seriously. If you don’t urinate for hours after you are done and feel/look like you’re swelling like a water balloon – go to the hospital immediately.

Part Four – The Danger Of Running Too Fast

One final parting shot on heat management: it is impossible to run your personal peak performance split times in the hottest conditions. One of the major factors in an athlete falling victim to the heat is an unwillingness to adjust pace projections (i.e., back off of your goal pace) in a hot race. Once the body temperature climbs over 100 degrees, the body shunts blood away from the gut and to the skin for cooling purposes – this is a primary cause of stomachs “shutting down” on hot days and is a precursor to heat stroke. The best solution for avoiding this is simply to slow down during the heat of the day. Realistically assess what you’re capable of on a perfect day, and combine that with an honest assessment of how heat acclimated you have become through training. A highly heat acclimated athlete might experience a 5% slowdown on race day, whereas a non-heat-trained runner might be slowed down 10-15% or more. Adjusting your pace to accommodate for this will help you avoid the dreaded DNF due to race mismanagement.

Ideally, all of the strategies reviewed above should be practiced in training so you can determine your own personal fluid loss and electrolyte replacement guidelines. Only through experimentation (and failure) can you find what’s right for you. If you’re like me, the moment you find the perfect balance of things, they change. So learning your body’s signals and symptoms for optimal heat management should be a primary goal of every ultrarunner.


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