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Heat Acclimation Training

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[[File:2013 Badwater.jpg|right|thumb|500px|I've done quite a bit of [[Running in the Heat]], from North Carolina's brutal summers, to winning the [[2010 Keys 100]] or pacing Chris Moon at the [[2013 Pacing Badwater 135| Badwater 135]].]]
Heat acclimation training can improve performance in hot and cold conditions. It also helps protect against heat injury and is particularly important when training for spring races. However, heat adaptation training can be dangerous , and care must be taken to avoid injury or death.
Training for a spring race requires extra caution as you will have been training through the winter and be unprepared for warm conditions. While a spring race may be cool, there is also a risk of conditions that are warm enough (above 40f) to impair performance (see [Impact of Heat on Marathon Performance] for more details). Heat acclimation training, sometimes called heat adaptation training, can prepare you for these warmer conditions. This type of training is also valuable if you are traveling to a warmer climate for a race, or if you are training in the cool part of the day for a race in the warmer times. In addition, heat acclimation can improve cold weather performance. One study<ref name="performance"/> showed that heat acclimation improved performance in the cold by 6% and by 8% in heat.
The following advice should be used as guidance for heat acclimation training. Please use caution and common sense.
* Like any new training routine, start off slowly and build up both duration and intensity over time.
* Be Measure your core temperature, ideally 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.* Beware a rapid rise in core temperature. Your temperature could continue to rise for a while after you stop exercising, which can be dangerous. * Aim for a core temperature of 38.5c/101.3f and do not let your core temperature go over 39.0c/102.2f. This is based on my review of heat adaptation studies shown below. * Your core temperature should rise over about 30 minutes to your target core temperature. * In addition to monitoring your core temperature, be aware of how you are feeling and avoid pushing too hard.
* Build up to exercising at 50% [[VO2max]] or above<ref name="Armstrong-1991"/>. 50% of [[VO2max]] is about 70% of maximum [[Heart Rate]]<ref name="swain"/> or "very slow running"<ref name="brianmac"/>.
* Use gradually increasing periods from 30 to 100 minutes over 10 to 14 days<ref name="Shapiro"/>
* Maintain hydration levels, as dehydration may impair key adaptations, such as increased sweat rate<ref name="TraversNichols2020"/>.
* Once gained, heat adaptation can be maintained for at least a month by training in the heat every five days<ref name="PryorPryor2019"/>. Without continued heat exposure, it's estimated that 2.5% of adaptation is lost each day<ref name="DaanenRacinais2017"/>.
* Don't combine heat and altitude training as the altitude may impair heat adaptation<ref name="McCleaveSlattery2019"/>.
=Fellrnr Heat Suit=
This 'heat suit' will allow for heat training even in quite cool conditions.
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This heat suit works by preventing the body cooling itself, so it increases the risk of heat stroke. If you overheat wearing this heat suit, you may not cool off after you collapse. Please be careful taking this approach, and start off with very low intensity exercise. Build up the duration and intensity very gradually, and monitor for warning signs. Please be careful, as I've had some close calls using this technique and it is dangerous. See "Symptoms of Heat Stroke" above.
|[[File:HeatSuit4.JPG|none|thumb|x300px|A second waterproof or windproof layer that traps the body's heat in the insulation layer. In addition, wear hat, gloves and ideally a neck warmer or face mask.]]
This combination will prevent most of the majority of heat escaping your body.
=Steam Shower=
[[File:SteamShower.JPG|none|thumb|300px|My steam shower, with a nice mosaic and a bench to relax on.]]
=The Science of Heat Acclimation=
For those who want to know more details about heat acclimation, here is a summary of the scientific data.
==Core Temperature for Heat Acclimation==
While most studies specified an ambient temperature and humidity, there are some that specified a target core temperature and time. This suggests that a core temperature of 38.5c/101.3f is a reasonable target and should be safe.
* Target core temperature of 38.5c/101.3f for 90 minutes, with the target temperature reached over about 30 minutes<ref name="GarrettGoosens2009"/><ref name="GarrettCreasy2011"/><ref name="NealCorbett2016"/><ref name="PattersonStocks2004"/>.
* Target core temperature of just over 39.0c/102.2f, for 2x 50 minutes with 10 minute recovery<ref name="KuennenGillum2011"/> or for 2 hours<ref name="KirbyConvertino1986"/>
* Target core temperature of 38.5c/101.3f or 39.0/102.2f for 90 minutes <ref name="GibsonMee2015"/> (similar results.)
* Passive heat exposure with core temperatures of 38.5c/101.3f to 39.0/102.2f for 2 hours<ref name="BeaudinWalsh2012"/>
* One study explicitly set a core temperature limit of 39.7c/103.4f<ref name="GibsonTurner2015"/>, but didn't give the rationale for that cut off.
The diagnostic criteria for heat stroke is 40c/104f<ref name="Expert2016"/>.
==Changes with heat acclimation==
Heat acclimation will produce a number of several benefits
* Increased blood volume<ref name="NielsenHales1993"/>.
* Sweating occurs at lower temperatures<ref name="Noakes"/>.
* The ability to consume and absorb more fluids (anecdotal evidence only).
==Notes on Heat Acclimatization==
* Younger runners do better in the heat than older runners , but training can negate this<ref name="Armstrong-1991"/>
* Acclimation is faster in fitter athletes<ref name="Armstrong-1991"/>
* On return to a cool climate, acclimation lasts for about a week, then decays<ref name="Armstrong-1991"/>
<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 [ 00223751], doi [ 10.1113/jphysiol.2004.063289]</ref>
<ref name="KirbyConvertino1986">C. R. Kirby, V. A. Convertino, Plasma aldosterone and sweat sodium concentrations after exercise and heat acclimation, Journal of Applied Physiology, volume 61, issue 3, 1986, pages 967–970, ISSN [ 8750-7587], doi [ 10.1152/jappl.1986.61.3.967]</ref>
<ref name="Expert2016">Expert consensus on standardized diagnosis and treatment for heat stroke, Military Medical Research, volume 3, issue 1, 2016, ISSN [ 2054-9369], doi [ 10.1186/s40779-015-0056-z]</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 [ 8750-7587], doi [ 10.1152/japplphysiol.00332.2015]</ref>
<ref name="BeaudinWalsh2012">Andrew E. Beaudin, Michael L. Walsh, Matthew D. White, Central chemoreflex ventilatory responses in humans following passive heat acclimation, Respiratory Physiology & Neurobiology, volume 180, issue 1, 2012, pages 97–104, ISSN [ 15699048], doi [ 10.1016/j.resp.2011.10.014]</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 [ 09057188], doi [ 10.1111/sms.12526]</ref>
<ref name="GibsonMee2015">Oliver R. Gibson, Jessica A. Mee, James A. Tuttle, Lee Taylor, Peter W. Watt, Neil S. Maxwell, Isothermic and fixed intensity heat acclimation methods induce similar heat adaptation following short and long-term timescales, Journal of Thermal Biology, volume 49-50, 2015, pages 55–65, ISSN [ 03064565], doi [ 10.1016/j.jtherbio.2015.02.005]</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 [ 1439-6319], doi [ 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 [ 1439-6319], doi [ 10.1007/s00421-009-1182-7]</ref>
<ref name="KuennenGillum2011">Matthew Kuennen, Trevor Gillum, Karol Dokladny, Edward Bedrick, Suzanne Schneider, Pope Moseley, Thermotolerance and heat acclimation may share a common mechanism in humans, American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, volume 301, issue 2, 2011, pages R524–R533, ISSN [ 0363-6119], doi [ 10.1152/ajpregu.00039.2011]</ref>
<ref name="McCleaveSlattery2019">Erin L. McCleave, Katie M. Slattery, Rob Duffield, Philo U. Saunders, Avish P. Sharma, Stephen Crowcroft, Aaron J. Coutts, Impaired Heat Adaptation From Combined Heat Training and "Live High, Train Low" Hypoxia, International Journal of Sports Physiology and Performance, volume 14, issue 5, 2019, pages 635–643, ISSN [ 1555-0265], doi [ 10.1123/ijspp.2018-0399]</ref>
<ref name="Armstrong-1991"> LE. Armstrong, CM. Maresh, The induction and decay of heat acclimatisation in trained athletes., Sports Med, volume 12, issue 5, pages 302-12, Nov 1991, PMID [ 1763248]</ref>
<ref name="Shapiro"> Y. Shapiro, D. Moran, Y. Epstein, Acclimatization strategies--preparing for exercise in the heat., Int J Sports Med, volume 19 Suppl 2, pages S161-3, Jun 1998, doi [ 10.1055/s-2007-971986], PMID [ 9694427]</ref>
<ref name="TraversNichols2020">Gavin Travers, David Nichols, Nathan Riding, José González-Alonso, Julien D. Périard, Heat Acclimation with Controlled Heart Rate, Medicine & Science in Sports & Exercise, 2020, pages 1, ISSN [ 0195-9131], doi [ 10.1249/MSS.0000000000002320]</ref>
<ref name="DaanenRacinais2017">Hein A. M. Daanen, Sebastien Racinais, Julien D. Périard, Heat Acclimation Decay and Re-Induction: A Systematic Review and Meta-Analysis, Sports Medicine, volume 48, issue 2, 2017, pages 409–430, ISSN [ 0112-1642], doi [ 10.1007/s40279-017-0808-x]</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 [ 0090-3493], doi [ 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 [ 1529-7535], doi [ 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 [ 0749-5161], doi [ 10.1097/PEC.0b013e31802c61e6]</ref>

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