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==Introduction==[[File:Running In The Heat M.jpg|right|thumb|500px|Running in the heat is far more stressful and can be dangerous.]] __NOTOC__Running in the heat is much harder than running in cooler temperatures, reducing performance and creating serious health risks. Without preparation The simple guidelines are to slow up and avoid pushing the heat can be punishing or even dangerous. The most important step is pace, drink to thirst, and to realize that running in dress for the heat requires just as much care as running in extreme coldconditions. ==Guidelines for Running in the Heat can kill==* '''Don't die'''. Running is generally a pretty safe sport, but there are some serious hazards to running in hot conditions. ** '''Heat stroke. '''If your core temperature gets too high, you can suffer from heat stroke. Runners who get heat stroke typically ignore the heat can killwarning signs and push on until they collapse. Risk is higher with shorter distances and faster paces, such as 5K where the bodies protective mechanisms that normally cause us to slow down rise in core temperature can be ineffectiveextremely rapid but can happen at the marathon distance as well. The key to avoiding heat stroke is to take it easy and don't push hard (see below on "go slower"), especially if you're new to running. There are a number You should watch out for the warning signs of risk factors for serious heat injuryoverheated listed below. Note that some antidepressant medications have been linked to heatstroke.* Being overweight* '''Dehydration. '''Contrary to expectations, it's tough to die from dehydration unless you're running in a remote location. A runner died from dehydration in 2004, as fat but they were running in the Grand Canyon in July where the temperatures can act as an insulatorhit 120f in the sun. If you have access to drinks, dehydration is self-limiting. Contrary to popular belief, which has been promoted by the sports drink industry, the evidence is that mild dehydration (<=4%) doesn't impact performance<ref name="Goulet2012"/><ref name="Goulet2011"/>. See [[The Science Of Hydration]] for details.* Being untrained* '''Hyponatremia. ''' Unlike dehydration, drinking too much is far more likely to be fatal. This condition, called [[Hyponatremia]], as fitness gives some heat adaptation has killed several runners over the unfit, years. Drink to thirst and also teaches the mind some keep your salt intake high. Adding 1/4 teaspoon of salt to each quart/liter of drink helps offset the danger signs of heat problemselectrolyte loss (most sports drinks don't contain enough salt to be noticeable.) Be careful about drinking cold drinks to lower your body temperature, as this can lead to overdrinking. See [[Practical Hydration]] for details.* Lack of heat acclimatization* '''Sunburn. ''' Not only does sunburn cause long-term health issues, which both gives protection from it can also cause more immediate problems with your body's temperature control. Burned skin doesn't sweat so well in the heat , and also teaches in colder conditions burned skin can't contract the mind capillaries to adjust the intensity based on reduce heatloss. * Thinking '''Adapt'''. There are various changes you can run faster than you can in the conditionsmake to your running that will make summer running easier. * Having suffered from heat illness before* Ignoring warning signs, such as weakness, clumsiness, stumbling, nausea, dizziness, apathy or aggression'''Take your temperature'''. However, runners that suffer heat stroke may exhibit none, or only one The most accurate way of these warning signsmeasuring your core temperature is with an in-ear infrared sensor<ref name="EricksonKirklin1993"/><ref name=Staying Alive in the Heat="DevrimKara2007"/><ref name="NimahBshesh2006"/>. I use a Braun ThermoScan and I've been pleased with it. The best advice seems to be to take things cautiously if you are not used to running in the heat** '''Go slower. Pushing yourself harder than normal in familiar '''With increased heatstress, or attempting to run normally in heat you 'll be slower. In fact, the optimum temperature for performance is generally about 40f/5c, and temperatures above this are not used likely to is dangerousslow you down. Traveling With mild temperatures (40-70f/5-20c) you're more likely to feel tired rather than hot as your mind shuts down muscle recruitment to a warmer area for a race is especially riskyprevent overheating. At higher temperatures, the impact becomes steadily greater. If your core temperature goes above 38.5c/101. 3f you should ease off or stop exercising until you cool off<ref name="GarrettGoosens2009"/><ref name=Tips for Running in the Heat"GarrettCreasy2011"/><ref name="NealCorbett2016"/><ref name="PattersonStocks2004"/>. If your temperature goes above 39.7c/103.4f you should terminate your activity and cool off as soon as possible<ref name="GibsonTurner2015"/>. See [[Impact of Heat on Marathon Performance]] for some guidelines on how much heat changes pace.* Get used to running * '''Acclimate'''.''' '''With acclimation, you will do better in the heat slowly, though you'll never do as well as you will in cool conditions. Heat acclimation produces many benefits, including increased blood volume, more rapid onset of sweating, reduced electrolyte levels at moderate sweat rates, and more. See [[Heat Acclimation Training]] for more details* Check the temperature and humidity before * '''Take breaks'''.''' '''Taking [[Walking Breaks]] can provide time to cool off, allowing you runto maintain your training distance. Knowing what to expect Running a short route repeatedly can help give you adjust your paceaccess to drinks and ice, as well as providing a natural break. Remember that humidity has You can check for [[Blister Prevention| blisters]] which can be more of a big impact on your ability problem in hot conditions. If you're looking to do speedwork, [[Interval Training]] is far better than tempo runs as the rest period between intervals allows you to cool off. However, be cautious with faster paced intervals like [[Tabata High Intensity Interval Training| Tabata HIIT]], as the faster pace can cause your core temperature to spike dangerously high.* * '''Avoid the heat'''.''' '''Run in the cooler parts of the day. Early such as early morning and later in the evening work well, avoiding late afternoon is often . Also aim to avoid the sun both by running shady routes and choosing the worstright time of day. (Remember sunburn not only has long term health risks, it also reduces your ability to control your core temperature.) * Stay Hydrated'''Dress for the conditions'''. The entry on [[Practical Hydration]] covers hydration What you wear can make a big difference to your performance, comfort, and electrolyteseven safety. Remember that electrolytes are However, you must dress for the conditions, as important as water for staying hydratedthe humidity and sun change things. Running in high and low humidity conditions is rather different. [[Hyponatremia]] can kill!* Cold drinks can also Evaporation will help lower your body temperaturekeep you cool in low humidity, but donit't drink too much without electrolytes s quite ineffective when the humidity is higher. (see above tip In the notes below, low heat is roughly <85f/30c, moderate is 85-100f/30c-40c, extreme is >100f/40c, though details will depend on hydrationyour height and weight, as noted in [[Running Heat Model]].)* Wear white* '''Moderate heat with low humidity'''. It may not be your favorite color''' '''When the humidity is low, but it is the coolestevaporation will help keep you cool.* Thin, form fitting clothing like [[Under Armor Heat Gear Top| UA's heat gear]] in white can spread out sweat over a greater area and keep you cooler than bare skin. * Wear * '''Extreme heat with low humidity'''.''' '''When the heat becomes more extreme your sweat rate may not be enough to keep you cool. Under these conditions it becomes worthwhile to wear thicker clothing that will hold more water and spray yourself off. At [[2014 Badwater 135| Badwater]] I wore a loose long-sleeved shirt that I kept soaked, which made a huge difference. When the heat is above core body temperature, air movement over dry skin will heat rather than cool your body, so it's only when you're wet that wind will help. ** '''Low heat with high humidity'''.''' '''These conditions can be deceiving, as the overall heat stress is much higher than you might expect. When the humidity is close to 100%, even small changes of temperature have a big impact on the fastest pace you can maintain without overheating. Cooling in these conditions comes predominantly from air movement across your skin (whiteconvection), not evaporation. Your best option is to wear as little as possible in order to expose your skin to the air, and clothing can easily act as an insulator. If you need to cover up because of the sunlight, then wearing very loose-fitting clothes that don't interfere with air movement may be an option. Ideally this loose clothing may act as a radiator for the heat, though in practice this is hard to achieve. Consider thin, form fitting clothes as another approach, but it needs to be as thin as possible. Consider applying ice to provide direct cooling (see below) hat. Wind will help cool you off. ** '''Moderate heat with moderate humidity'''.''' '''The combination of the heat and humidity can be both brutal and intractable. The humidity limits the cooling from evaporation and the warm air limits the cooling from convection. In very hotthese conditions, applying ice is one of the few ways of cooling off, and without it running can become impractical. Clothing should be selected to spread out the meltwater from the ice, so thin, sunny form fitting clothing is ideal. ** '''Extreme heat with high humidity'''.''' '''These conditionsare relatively rare, but there comes a point where running becomes impractical and ill advised. ** '''Daytime'''.''' '''As you probably know, white clothing reflects heat where black absorbs heat. If you're in direct sunlight, then wearing white is critical, and even in partially shady conditions white clothing is an advantage. A white hat should be used and consider a 'legionaries cap' can to help protect your neck and face.* Adjust your pace for the heat. See [[Impact of Heat on Marathon PerformanceRunning Hats]] for some guidelinesmore details. * Protect yourself from * '''Nighttime'''.''' '''After dark it may be better to wear dark clothing to help radiate more heat. =Heat and Fatigue=It is generally accepted that exercise at a constant effort will be voluntarily terminated once the UVcore body temperature reaches about 40c/104f<ref name="Tucker-2008"/>. Either wear sunscreenHowever, if subjects are allowed to vary their pace freely, or cover upthey will preemptively reduce their exercise intensity to prevent their core temperature form reaching the critical point<ref name="Tucker-2008"/>. Remember One mechanism for this reduction is that skin cancer fewer [[Muscle|muscle fibers]] are recruited in hot conditions, even before the core body temperature starts to rise<ref name="Tucker-2004"/>. Elevated core temperature reduces the voluntary maximum force generated, though it is unimpaired when electrical stimulation is used, indicating the central nervous system is responsible<ref name="Nybo-2008"/> . When exercising at a nasty way to dieconstant [[Rating of Perceived Exertion]], subjects steadily reduced their power output at 59f/15c, 77f/25c or 95f/35c even though their perception of their temperature comfort remained constant<ref name="Tucker2006"/>. * Wear sunglasses with UV protection==Mechanisms==Exercise in the heat burns more carbohydrate than in cool conditions<ref name="Mündel-2008"/> . I love my Oakley Half Jackets ;}* Wearing However, it is not clear to me if this is because of a 'cool off bandanna' filled with ice works wondersdirect change in the use of carbohydrate, or if the hot conditions reduce [[VO2max|V̇O₂max]] and therefore the exercise intensity is effectively increased. Exercise in the heat also burns more muscle [[Protein]]<ref name="Snow-1993"/><ref name="Marino-2001"/>, and the waste products from this [[Protein]] metabolism could result in mental fatigue due to a rise in [http://wwwen.zombierunnerwikipedia.comorg/storewiki/product152Gamma-Aminobutyric_acid GABA]<ref name="Mündel-2008"/>.html* Pouring water over yourself =Heat Stroke=Running in the heat can help slightly* Watch out for [[Blister Prevention|blisters]] kill, as your feet are more likely the body's protective mechanisms that normally cause us to slow down can be wet than in cooler conditionsineffective. There are a number of risk factors for heat stroke. # Being overweight, as fat can act as an insulator. * Run in # Being untrained, as fitness gives some heat adaptation over the shade unfit. # Lack of possibleheat acclimatization, as this acclimatization gives some protection from the heat. * Plan ahead; carry more drink with # Thinking you can run faster than you expect to needcan in the conditions. # Having suffered from heat illness before.# Ignoring warning signs (see below). * For speed workBeing overweight, prefer shorter intervals unfit and attempting to run hard can be very cautiousa catastrophic combination. Intense exercise can spike your core temperature and this rise can continue even after collapse as the heat from the muscles warms the blood while the fat reduces the cooling effect. * Take walking breaks =The Warning Signs of Overheating=The best advice seems to be to cool off take things cautiously if you are having problems* Watch not used to running in the heat. Pushing yourself harder than normal in familiar heat, or attempting to run normally in heat you are not used to is dangerous. Traveling to a warmer area for a race is especially risky. Look out for the following warning signs listed above, and if you have any doubts, slow down or stop and cool off. * Nausea or vomiting. These symptoms can occur before true heatstroke, as running makes digestion harder.* Weakness. An unusual muscular weakness could be due to low blood sugar, but elevated core temperature also creates weakness.* Headache. This can also be caused by dehydration, or low blood sugar. I find nausea is Having had headaches from each of the first sign three causes, I have found the type of overheating and headache is my first sign of dehydrationdifferent. My limited experience is that a headache caused by heat is particularly painful and intense. * Carry a cell phone. If you get it wrong, you can call for helpDizziness or confusion. (This is true in many situationsa serious symptom that suggests either extremely low blood sugar or heatstroke.)* Changing your running route so Flushed/Hot Skin. I've found that you are doing several shorter loops or out-and-backs. You can then cache some drinks for each section rather than carrying enough for an early warning sign is the whole runfeeling that my skin is burning, especially my face.* Ice bandanas can also be used around Panting. Another symptom I've found of overheating is that my [[Breathing]] becomes labored beyond what is reasonable for the wristsexercise intensity. (Jim P)* Ice under the hatCore Temperature. The only sure test is to check your core temperature using something like an in-ear thermometer. Using a mouth thermometer may not be accurate if you've been [[Breathing]] hard. (Jim P)* If you are doing loopshave any doubts, keep a spare shirt stop and check your temperature. Avoid [[High Intensity Interval Training]] in the heat; the intense work can spike your core temperature too high too quickly for you to recover. It's possible that a cooler full runner that suffers heat stroke may exhibit none, or only one of icethese warning signs.=Using Ice=Ice can be a huge help in hot, and switch every loophumid conditions. I'd recommend trying a [[Jimbo Bandana]] while running (Jim Pas well as for [[Precooling]].)* You can also put ice under a hat, though this can be quite painful when the cold hits your scalp. Even holding some ice in your hand, or holding a cold water bottle can [http:help<ref name="Hsu-2005"/>. Pouring water over your head, neck and body is an alternative, but watch out for the shock of the temperature differential. It's important to '''never use gel packs''', only frozen water! Gel packs start off too cold, causing frostbite and skin damage, then warm up too quickly. If you use ice, it will start off just below freezing and then maintain that temperature until it's melted. =The effect of clothing color=A study<ref name="ShkolnikTaylor1980"/www> comparing clothing color in hot conditions (38C) and strong sun showed that black clothes result in 2.ncbi5x the gain heat from the sun compared with white clothes.nlmTan clothing of a military uniform gained 1.nih7x more than white clothes and just shorts (semi-nude) gained 2.gov/pubmed/15855685 help]2x more.* Some antidepressant medications have been linked Therefore, it's important to heatstrokewear white clothes in hot sunny conditions.=Tight or lose clothing?=The study<ref name="ShkolnikTaylor1980"/> of clothing color used black and white versions of the traditional Bedouin clothing, which has two layers of material and allows air to flow freely between them, creating a chimney like effect. This clothing mitigated most of the extra heat absorbed from the black clothing, as the hotter air was able to escape. This suggests that lose clothing may be an advantage, but only if the air can freely circulate. Also, the study used stationary people, so the benefit of loose clothing may not transfer to exercising athletes.=See Also==