==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. Without preparation the heat can be punishing or even dangerous, reducing performance and creating serious health risks. The most important step is simple guidelines are to realize that running in slow up and avoid pushing the heat requires just as much care as running in extreme coldpace, drink to thirst, and to dress for the conditions. ==Guidelines for Running in the Heat can kill==* '''Don't die'''. Running in the heat can killis generally a pretty safe sport, as the bodies protective mechanisms that normally cause us but there are some serious hazards to slow down can be ineffectiverunning in hot conditions. There are a number of risk factors for serious heat injury ** Being overweight'''Heat stroke. '''If your core temperature gets too high, as fat you can act as an insulatorsuffer from heat stroke.* Being untrained, as fitness gives some Runners who get heat adaptation over stroke typically ignore the unfit, warning signs and also teaches the mind some of push on until they collapse. Risk is higher with shorter distances and faster paces, such as 5K where the rise in core temperature can be extremely rapid but can happen at the danger signs of heat problemsmarathon distance as well.* Lack of The key to avoiding heat acclimatizationstroke is to take it easy and don't push hard (see below on "go slower"), which both gives protection from the heat and also teaches the mind especially if you're new to adjust the intensity based on heatrunning. * Thinking you can run faster than you can in You should watch out for the conditionswarning signs of overheated listed below. Note that some antidepressant medications have been linked to heatstroke. * Having suffered from heat illness before* Ignoring warning signs, such as weakness, clumsiness, stumbling, nausea, dizziness, apathy or aggression* '''Dehydration. However '''Contrary to expectations, runners that suffer heat stroke may exhibit noneit's tough to die from dehydration unless you're running in a remote location. A runner died from dehydration in 2004, or only one of these warning signs==Staying Alive but they were running in the Grand Canyon in July where the Heat==The best advice seems to be to take things cautiously if you are not used to running temperatures can hit 120f in the heatsun. Pushing yourself harder than normal in familiar heat, or attempting to run normally in heat If you are not used have access to drinks, dehydration is dangerousself-limiting. Traveling Contrary to a warmer area for a race popular belief, which has been promoted by the sports drink industry, the evidence is especially risky. that mild dehydration (<=4%) doesn't impact performance<ref name=Tips for Running in the Heat"Goulet2012"/><ref name==* Get used to running in the heat slowly. See "Goulet2011"/>. See [[Heat Acclimation TrainingThe Science Of Hydration]] for more details. * Check the temperature and humidity before you run* '''Hyponatremia. Knowing what ''' Unlike dehydration, drinking too much is far more likely to expect can help you adjust your pacebe fatal. Remember that humidity This condition, called [[Hyponatremia]], has a big impact on killed several runners over the years. Drink to thirst and keep your ability salt intake high. Adding 1/4 teaspoon of salt to cool off.* Run in the cooler parts each quart/liter of drink helps offset the day. Early morning and later in the evening work well, late afternoon is often the worstelectrolyte loss (most sports drinks don't contain enough salt to be noticeable. * Stay Hydrated) Be careful about drinking cold drinks to lower your body temperature, as this can lead to overdrinking. The entry on See [[Practical Hydration]] covers hydration and electrolytes. Remember that electrolytes are as important as water for staying hydrateddetails. Hyponatremia can kill!* Cold drinks can also help lower * '''Sunburn. ''' Not only does sunburn cause long-term health issues, it can also cause more immediate problems with your body 's temperature, but doncontrol. Burned skin doesn't drink too much without electrolytes (see above tip on hydration)* Wear white. It may not be your favorite colorsweat so well in the heat, but it is and in colder conditions burned skin can't contract the coolestcapillaries to reduce heat loss.* [[Under Armor Heat Gear Top]] in white '''Adapt'''. There are various changes you can keep you cooler than bare skinmake to your running that will make summer running easier. * Wear a (white) hat. In very hot, sunny conditions, a * ''legionaries cap' can help protect Take your neck and facetemperature'''.* Adjust The most accurate way of measuring your pace for the heat. See [[Impact of Heat on Marathon Performance]] for some guidelinescore temperature is with an in-ear infrared sensor<ref name="EricksonKirklin1993"/><ref name="DevrimKara2007"/><ref name="NimahBshesh2006"/>. I use a Braun ThermoScan and I've been pleased with it. * Protect yourself from the UV* '''Go slower. Either wear sunscreen'''With increased heat stress, or cover upyou'll be slower. Remember that skin cancer In fact, the optimum temperature for performance is a nasty way generally about 40f/5c, and temperatures above this are likely to dieslow you down. * Wear sunglasses with UV protection. I love my Oakley Half Jackets ;}* Wearing a With mild temperatures (40-70f/5-20c) you'cool off bandanna' filled with ice works wondersre more likely to feel tired rather than hot as your mind shuts down muscle recruitment to prevent overheating. http: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="GarrettCreasy2011"/><ref name="NealCorbett2016"/www><ref name="PattersonStocks2004"/>.zombierunnerIf your temperature goes above 39.com7c/store/product152103.html* Pouring water over yourself can help slightly* Watch out for 4f you should terminate your activity and cool off as soon as possible<ref name="GibsonTurner2015"/>. See [[Blister Prevention|blistersImpact of Heat on Marathon Performance]] as your feet are more likely to be wet than in cooler conditionsfor some guidelines on how much heat changes pace. * Run in the shade of possible. * Plan ahead; carry more drink with '''Acclimate'''.''' '''With acclimation, you than will do better in the heat, though you expect to need. * For speed work'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, prefer shorter intervals and be very cautiousmore. * Take walking See [[Heat Acclimation Training]] for more details** '''Take breaks '''.''' '''Taking [[Walking Breaks]] can provide time to cool off if , allowing you are having problems* Watch out for the warning signs listed aboveto maintain your training distance. I find nausea is the first sign I have of overheating Running a short route repeatedly can give you access to drinks and headache is my first sign of dehydration. * Carry ice, as well as providing a cell phonenatural break. If you get it wrong, you You can call check for help. (This is true [[Blister Prevention| blisters]] which can be more of a problem in many situationshot conditions.)* Changing your running route so that If you are doing several shorter loops or out-and-backs. You can then cache some drinks for each section rather 're looking to do speedwork, [[Interval Training]] is far better than carrying enough for tempo runs as the whole runrest period between intervals allows you to cool off.* Ice bandanas can also However, be used around cautious with faster paced intervals like [[Tabata High Intensity Interval Training| Tabata HIIT]], as the wristsfaster pace can cause your core temperature to spike dangerously high. (Jim P)* Ice under * '''Avoid the hatheat'''. (Jim P)* If you are doing loops''' '''Run in the cooler parts of the day such as early morning and later in the evening, avoiding late afternoon. Also aim to avoid the sun both by running shady routes and choosing the right time of day. (Remember sunburn not only has long term health risks, keep a spare shirt in a cooler full of ice, and switch every loop. (Jim P)==See Also==* [[Heat Index For Runnersit also reduces your ability to control your core temperature.) * '''Dress for the conditions'''. What you wear can make a big difference to your performance, comfort, and even safety. However, you must dress for the conditions, as the humidity and sun change things. Running in high and low humidity conditions is rather different. Evaporation will help keep you cool in low humidity, but it's quite ineffective when the humidity is higher. (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 your height and weight, as noted in [[Running Heat Model]].)** '''Moderate heat with low humidity'''.''' '''When the humidity is low, evaporation will help keep you cool. Thin, form fitting clothing like [[Under Armor Heat Gear Top| UA's heat gear]] can spread out sweat over a greater area and keep you cooler than bare skin. ** '''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 (convection), 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). 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 these 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, form fitting clothing is ideal. ** '''Extreme heat with high humidity'''.''' '''These conditions are 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' to help protect your neck and face. See [[Running Hats]] for more details.** '''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 core body temperature reaches about 40c/104f<ref name="Tucker-2008"/>. However, if subjects are allowed to vary their pace freely, they will preemptively reduce their exercise intensity to prevent their core temperature form reaching the critical point<ref name="Tucker-2008"/>. One mechanism for this reduction is that 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 constant [[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"/>.==Mechanisms==Exercise in the heat burns more carbohydrate than in cool conditions<ref name="Mündel-2008"/> . However, it is not clear to me if this is because of a direct change in the use of carbohydrate, or if the hot conditions reduce [[VO2max|V̇O<sub>2</sub>max]] 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://en.wikipedia.org/wiki/Gamma-Aminobutyric_acid GABA]<ref name="Mündel-2008"/>.=Heat Stroke=Running in the heat can kill, as the body's protective mechanisms that normally cause us to slow down can be ineffective. There are a number of risk factors for heat stroke. # Being overweight, as fat can act as an insulator. # Being untrained, as fitness gives some heat adaptation over the unfit. # Lack of heat acclimatization, as this acclimatization gives some protection from the heat. # Thinking you can run faster than you can in the conditions. # Having suffered from heat illness before.# Ignoring warning signs (see below).Being overweight, unfit and attempting to run hard can be a 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. =The Warning Signs of Overheating=The best advice seems to be to take things cautiously if you are 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, 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. Having had headaches from each of the three causes, I have found the type of headache is different. My limited experience is that a headache caused by heat is particularly painful and intense.* Dizziness or confusion. This is a serious symptom that suggests either extremely low blood sugar or heatstroke.* Flushed/Hot Skin. I've found that an early warning sign is the feeling that my skin is burning, especially my face.* Panting. Another symptom I've found of overheating is that my [[Breathing]] becomes labored beyond what is reasonable for the exercise intensity.* Core 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.If you have any doubts, 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 runner that suffers heat stroke may exhibit none, or only one of these warning signs.=Using Ice=Ice can be a huge help in hot, humid conditions. I'd recommend trying a [[Jimbo Bandana]] while running (as 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 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"/> comparing clothing color in hot conditions (38C) and strong sun showed that black clothes result in 2.5x the gain heat from the sun compared with white clothes. Tan clothing of a military uniform gained 1.7x more than white clothes and just shorts (semi-nude) gained 2.2x more. Therefore, it's important to wear 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=* Running calculators** [[Running Heat Model]]** [[Perceived Temperature For Runners]]** [[Heat limited running pace]]** [[Optimum Running Temperature]]* [[Heat Acclimation Training]]* [[Impact of Heat on Marathon Performance]]=References=<references><ref name="ShkolnikTaylor1980">Amiram Shkolnik, C. Richard Taylor, Virginia Finch, Arieh Borut, Why do Bedouins wear black robes in hot deserts?, Nature, volume 283, issue 5745, 1980, pages 373–375, ISSN [http://www.worldcat.org/issn/0028-0836 0028-0836], doi [http://dx.doi.org/10.1038/283373a0 10.1038/283373a0]</ref><ref name="Snow-1993"> RJ. Snow, MA. Febbraio, MF. Carey, M. Hargreaves, Heat stress increases ammonia accumulation during exercise in humans., Exp Physiol, volume 78, issue 6, pages 847-50, Nov 1993, PMID [http://www.ncbi.nlm.nih.gov/pubmed/8311952 8311952]</ref><ref name="Marino-2001"> FE. Marino, Z. Mbambo, E. Kortekaas, G. Wilson, MI. Lambert, TD. Noakes, SC. Dennis, Influence of ambient temperature on plasma ammonia and lactate accumulation during prolonged submaximal and self-paced running., Eur J Appl Physiol, volume 86, issue 1, pages 71-8, Nov 2001, PMID [http://www.ncbi.nlm.nih.gov/pubmed/11820326 11820326]</ref><ref name="Mündel-2008"> T. Mündel, Exercise heat stress and metabolism., Med Sport Sci, volume 53, pages 121-9, 2008, doi [http://dx.doi.org/10.1159/000151554 10.1159/000151554], PMID [http://www.ncbi.nlm.nih.gov/pubmed/19209003 19209003]</ref><ref name="Nybo-2008"> Nybo, Lars. "Hyperthermia and fatigue." Journal of Applied Physiology 104.3 (2008): 871-878.</ref><ref name="Tucker-2008"> R. Tucker, Thermoregulation, fatigue and exercise modality., Med Sport Sci, volume 53, pages 26-38, 2008, doi [http://dx.doi.org/10.1159/000151548 10.1159/000151548], PMID [http://www.ncbi.nlm.nih.gov/pubmed/19208997 19208997]</ref><ref name="Tucker2006">R. Tucker, The rate of heat storage mediates an anticipatory reduction in exercise intensity during cycling at a fixed rating of perceived exertion, The Journal of Physiology, volume 574, issue 3, 2006, pages 905–915, ISSN [http://www.worldcat.org/issn/0022-3751 0022-3751], doi [http://dx.doi.org/10.1113/jphysiol.2005.101733 10.1113/jphysiol.2005.101733]</ref><ref name="Tucker-2004"> R. Tucker, L. Rauch, YX. Harley, TD. Noakes, Impaired exercise performance in the heat is associated with an anticipatory reduction in skeletal muscle recruitment., Pflugers Arch, volume 448, issue 4, pages 422-30, Jul 2004, doi [http://dx.doi.org/10.1007/s00424-004-1267-4 10.1007/s00424-004-1267-4], PMID [http://www.ncbi.nlm.nih.gov/pubmed/15138825 15138825]</ref><ref name="Hsu-2005"> AR. Hsu, TA. Hagobian, KA. Jacobs, H. Attallah, AL. Friedlander, Effects of heat removal through the hand on metabolism and performance during cycling exercise in the heat., Can J Appl Physiol, volume 30, issue 1, pages 87-104, Feb 2005, PMID [http://www.ncbi.nlm.nih.gov/pubmed/15855685 15855685]</ref><ref name="Goulet2012">E. D. B. Goulet, Effect of exercise-induced dehydration on endurance performance: evaluating the impact of exercise protocols on outcomes using a meta-analytic procedure, British Journal of Sports Medicine, volume 47, issue 11, 2012, pages 679–686, ISSN [http://www.worldcat.org/issn/0306-3674 0306-3674], doi [http://dx.doi.org/10.1136/bjsports-2012-090958 10.1136/bjsports-2012-090958]</ref><ref name="Goulet2011">E. D. B. Goulet, Effect of exercise-induced dehydration on time-trial exercise performance: a meta-analysis, British Journal of Sports Medicine, volume 45, issue 14, 2011, pages 1149–1156, ISSN [http://www.worldcat.org/issn/0306-3674 0306-3674], doi [http://dx.doi.org/10.1136/bjsm.2010.077966 10.1136/bjsm.2010.077966]</ref><ref name="EricksonKirklin1993">Roberta S. Erickson, Sharon K. Kirklin, Comparison of ear-based, bladder, oral, and axillary methods for core temperature measurement, Critical Care Medicine, volume 21, issue 10, 1993, pages 1528–1534, ISSN [http://www.worldcat.org/issn/0090-3493 0090-3493], doi [http://dx.doi.org/10.1097/00003246-199310000-00022 10.1097/00003246-199310000-00022]</ref><ref name="NimahBshesh2006">Marianne M. Nimah, Khaled Bshesh, Janice D. Callahan, Brian R. Jacobs, Infrared tympanic thermometry in comparison with other temperature measurement techniques in febrile children, Pediatric Critical Care Medicine, volume 7, issue 1, 2006, pages 48–55, ISSN [http://www.worldcat.org/issn/1529-7535 1529-7535], doi [http://dx.doi.org/10.1097/01.PCC.0000185476.35550.B2 10.1097/01.PCC.0000185476.35550.B2]</ref><ref name="DevrimKara2007">??lker Devrim, Ate?? Kara, Mehmet Ceyhan, Hasan Tezer, Ali Kerem Uluda??, Ali B??lent Cengiz, ??nci Yi??itkanl, G??lten Se??meer, Measurement Accuracy of Fever by Tympanic and Axillary Thermometry, Pediatric Emergency Care, volume 23, issue 1, 2007, pages 16–19, ISSN [http://www.worldcat.org/issn/0749-5161 0749-5161], doi [http://dx.doi.org/10.1097/PEC.0b013e31802c61e6 10.1097/PEC.0b013e31802c61e6]</ref><ref name="PattersonStocks2004">Mark J. Patterson, Jodie M. Stocks, Nigel A. S. Taylor, Sustained and generalized extracellular fluid expansion following heat acclimation, The Journal of Physiology, volume 559, issue 1, 2004, pages 327–334, ISSN [http://www.worldcat.org/issn/00223751 00223751], doi [http://dx.doi.org/10.1113/jphysiol.2004.063289 10.1113/jphysiol.2004.063289]</ref><ref name="GibsonTurner2015">Oliver R. Gibson, Gareth Turner, James A. Tuttle, Lee Taylor, Peter W. Watt, Neil S. Maxwell, Heat acclimation attenuates physiological strain and the HSP72, but not HSP90α, mRNA response to acute normobaric hypoxia, Journal of Applied Physiology, volume 119, issue 8, 2015, pages 889–899, ISSN [http://www.worldcat.org/issn/8750-7587 8750-7587], doi [http://dx.doi.org/10.1152/japplphysiol.00332.2015 10.1152/japplphysiol.00332.2015]</ref><ref name="GarrettCreasy2011">Andrew T. Garrett, Rob Creasy, Nancy J. Rehrer, Mark J. Patterson, James D. Cotter, Effectiveness of short-term heat acclimation for highly trained athletes, European Journal of Applied Physiology, volume 112, issue 5, 2011, pages 1827–1837, ISSN [http://www.worldcat.org/issn/1439-6319 1439-6319], doi [http://dx.doi.org/10.1007/s00421-011-2153-3 10.1007/s00421-011-2153-3]</ref><ref name="GarrettGoosens2009">Andrew T. Garrett, Niels G. Goosens, Nancy G. Rehrer, Mark J. Patterson, James D. Cotter, Induction and decay of short-term heat acclimation, European Journal of Applied Physiology, volume 107, issue 6, 2009, pages 659–670, ISSN [http://www.worldcat.org/issn/1439-6319 1439-6319], doi [http://dx.doi.org/10.1007/s00421-009-1182-7 10.1007/s00421-009-1182-7]</ref><ref name="NealCorbett2016">R. A. Neal, J. Corbett, H. C. Massey, M. J. Tipton, Effect of short-term heat acclimation with permissive dehydration on thermoregulation and temperate exercise performance, Scandinavian Journal of Medicine & Science in Sports, volume 26, issue 8, 2016, pages 875–884, ISSN [http://www.worldcat.org/issn/09057188 09057188], doi [http://dx.doi.org/10.1111/sms.12526 10.1111/sms.12526]</ref></references>[[Category:Beginners]][[Category:Advanced]][[Category:Training]][[Category:Racing]][[Category:Marathon]][[Category:Ultramarathon]] (An experimental chart)
