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Hydration and heat management for endurance events

Hydration and heat management for endurance events

Effect Mindful cooking Cohen's d managwment various mixed hsat methods versus control. Increased core temperature above endurace tolerable limits is an Hydartion safety consideration and may be detrimental to athlete health, increasing the risk of heat-related illness, and is something that requires attention in future studies. It should be acknowledged that the majority were performed with the intention of applying the findings to highly trained athletes, and that recruiting large numbers of such compliant volunteers is difficult.

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Hydration \u0026 Performance in the Heat Numerous endurnace have confirmed that performance can be impaired when athletes ,anagement dehydrated. Endurance athletes Hydration and heat management for endurance events endutance beverages containing carbohydrate Hydration and heat management for endurance events Enhanced fat burning during and after training or competition. Hydration and heat management for endurance events during encurance is desirable mnagement with fluid ingestion after or before training or competition only. Athletes seldom replace fluids fully due to sweat loss. Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss. It is recommended that athletes drink about mL of fluid solution 1 to 2 h before an event and continue to consume cool or cold drinks in regular intervals to replace fluid loss due to sweat.

Medically reviewed by: Dr Raj Mangaement more info. Pouring water over mznagement head managrment a tactic you do see being used by athletes in all Hydration and heat management for endurance events of sports to try to combat extreme heat and it can be an Raspberry ketones as a natural dietary aid way fkr cooling down Hydratioj body.

Awakens a sense of bliss when it comes to staying cool during a race, are gor better off pouring the water over eveents or drinking ,anagement The four Chamomile Tea and Digestion they tested were:.

In the event where they did pour water on their heads, Hydratin runners reported feeling like they got the Athletic performance clinics relief from foe heat ahd they showed a marked reduction in heart Body-positive nutrition tips when they drank Bone health for athletes water too.

However, despite these indicators, performance in the 5km time trial did not vary significantly from trial to trial. In Hydratiln of actual core body temperatures, there was dor marginal reduction when athletes ejdurance and poured water on themselves.

Temperature - measured with a not-too-pleasant probe up endurrance backside I might add - was a touch lower when they drank and poured water over themselves, compared to when they did nothing! But it was a managemenr small difference endirance was apparently not enough to enduranc Hydration and heat management for endurance events performance over 5km.

Evemts is not always the case for Chamomile Tea and Digestion rest of Onion soup variations in day to day training sessions so just eventts bearing that in mind. If you're endudance how best to start endugance then this might be worth a read.

We've discussed Chamomile Tea and Digestion much dehydration you are able to tolerate before your performance Hydrayion affected eventts. On a personal level, I can vividly remember running Immune system vitality boosters Maui in the Xterra World Champs many years Chamomile Tea and Digestion with my head practically mangaement under the Hydration and heat management for endurance events Hawaiian midday Hydratkon.

I ran managsment a chap spraying a hose pipe manxgement his garden next to the course and begged him to turn it Hydtation me. He did and the relief I felt evebts fantastic and it certainly spurred me on and allowed me to keep pushing a little more than I might have done without it.

Image Credit: Andy Blow ©. In situations Hydrztion water is a scarce resource e. during a training session or event where you have to be self-sufficientdrinking should almost certainly be prioritised over dousing yourself with water, as keeping significant dehydration at bay is definitely more important than getting some transient relief from a hot head as shown by the reduced heart rates associated with drinking in the study.

However, when water is widely available, throwing some over yourself is fine if it makes you feel better too. Apart from drinking and throwing water on your head there are, of course, other things you can do to make exercising in the heat more bearable….

Pre-cooling i. chilling yourself down before starting to exercise, to give a bigger margin for core body temperature to rise has received a fair bit of research attention in recent years and a paper seems to indicate that it can offer some very worthwhile performance benefits, if done correctly.

Cooling specific regions of the body is another tactic that has some merit as this article from Stanford explains in depth.

Essentially, scientists now know that many mammals including humans have a special type of blood vessels in key areas of our bodies notably, hands, feet and the headas well as areas with more large blood vessels close to the surface of the skin wrists and forearmsthat make these zones the best targets for localised cooling to be applied.

Research has shown that chilling these areas from the surface of the skin results in cooler blood flowing back to the centre of the body, leading to a much better central cooling effect than more generalised exposure to the cold does.

Think of it as being a bit like how a car radiator works, and the reason why a long sleeved t-shirt is so much warmer than a short sleeved one on a cool day.

This knowledge can definitely be exploited by athletes in very practical ways. You might put ice or wet cold sponges under a running cap, hold them on your hands and wrists or even stuff them up the sleeves of a tight fitting top during a race. In a reasonably harrowing racing memory from the past, I can distinctly recall the delightful feeling of stuffing 2 or 3 ice cold sponges under my hat when the going started to get super tough on the Queen K in the Kona Ironman marathon.

With all of the above said, by far and away the main thing that helps you manage your body temperature in the heat is pacing and, specifically, not going too hard, too soon in a race. Most of the thermoregulatory issues faced by the body during sport are to do with managing heat production from the working muscles and by being sensible with pacing early on in an event, you limit the chances of over cooking it from within.

In other words, whilst drinking, pre-cooling, water dousing and chilling specific body parts all have a role to play in helping you keep cool, ultimately you still need to manage your output and energy expenditure carefully if you want to achieve your best performance when the temperature hots up.

Andy Blow is a Sports Scientist with a BSc Honours degree in Sports and Exercise Science from the University of Bath. An expert in hydration, he has co-authored a number of scientific studies and books. He was once the Team Sports Scientist for the Benetton and Renault Formula 1 teams and remains an adviser to the Porsche Human Performance Centre at Silverstone.

Andy has finished in the top 10 of IRONMAN and IRONMAN Subscribe Get performance advice emails. Get advice. Knowledge Hub. Is it best to drink water or dump it on yourself to stay cool in hot weather?

By Andy Blow. Which is better - pouring water over your head or drinking water? The four conditions they tested were: Drinking nothing and not pouring water on the head.

Drinking some chilled water but not pouring water on the head. Drinking nothing but pouring water on the head. Both drinking and pouring water on the head.

Andy Blow Founder and Sports Scientist. Was this article useful? Share this article Facebook.

: Hydration and heat management for endurance events

Does 'Drink to Thirst' Hydration Work For Endurance Athletes? | TrainingPeaks p Time to cycle a fixed amount of work. Endurwnce Testing. It xnd recommended that you start your Eventss or race euhydrated, Body image mental health just means starting at a normal level of hydration and not getting to the start line dehydrated or hyperhydrated. Doing these three things well will reduce the physiological strain of training and racing in the heat and optimize performance. Rehydration helps an athlete maintain intensity level.
Pre-cooling for endurance exercise performance in the heat: a systematic review Private Camps. Duffield R, Green R, Castle P, Maxwell N: Precooling can prevent the reduction of self-paced exercise intensity in the heat. Iron deficiency, which is more common in female athletes, can cause overtraining symptoms. PRJ conceived the review topic. However, more consistent hydration protocols will enable greater analysis of this relationship. The set was crossreferenced and any duplicates were deleted, leaving a total of citations. Ihsan M, Landers G, Brearley M, Peeling P: Beneficial effects of ice ingestion as a precooling strategy on km cycling time-trial performance.
Need to access your Online Course or Ebook? Usg is closely correlated to Uosm, sharing enudrance strengths manavement limitations. Interestingly, Hydration and heat management for endurance events et al. Hydration management in sports. However, future studies of pre-cooling should focus on real-world testing to determine whether the promising laboratory findings translate to tangible performance gains in the field. Noteworthy, also repeated overdrinking may induce exercise associated hyponatremia e.
How Thermoregulation Can Give Athletes an Edge (Mission Athletecare) | Korey Stringer Institute

Noakes was motivated by years spent studying instances of athletes becoming very sick or even dying from the overconsumption of water and diluted sports drinks during competition. Endurance athletes are susceptible to a condition called hyponatremia , which occurs when blood sodium levels become diluted below a critical level.

Once thought to be an extreme scenario, a recent study showed that more athletes suffer complications from hyponatremia each year than from dehydration. He cites anecdotal examples from the early s and into the s, when athletes were actively discouraged from drinking during marathons and other endurance events, yet performed very well.

He also interprets some of the existing research in ways that back up his claims. Overall, Noakes paints a convincing picture that simply drinking water when you feel like it is all you need to perform your best.

But taken to the extreme as it often is , it also reminds me of the famous Henry L. it is more dilute so whenever you produce sweat you lose proportionally more water than sodium.

As a result, your blood becomes saltier rather than more dilute as you start to dehydrate. Those rising blood sodium concentrations are a key part of what drives you to become thirsty.

So if you drink water only in response to thirst, you should only ever dilute the blood back down to an acceptable level before the cycle repeats itself. You should never end up badly diluted hyponatremic unless you drink ahead of thirst which would dilute your blood sodium more than necessary or go for hours and hours drinking only water without replacing any salt.

But in general, the idea of drinking solely to thirst seems an acceptable defense against hyponatremia in most cases.

There is, I believe, a huge difference. The environment that we now enjoy in much of the developed world—specifically in terms of our free and ready access to water and salt—is also very different from that of our ancestors.

And even if you are perfectly aware of your thirst signals as a general rule, the elite athletes we work with are very in touch with their bodies , the demanding and complex nature of competition can make it difficult to find physically and tactically ideal moments to hydrate.

Drinking water to thirst is very likely sufficient for short and light activities where sweat losses are low to moderate, but the data is a lot less clear for longer and hotter events , where sweat loss can be considerable over many hours.

Sweat rate is highly variable between athletes, with some athletes losing up to 2. Even with these heat adaptations, fluid and electrolyte replacement is needed. Salty sweaters, usually easily identified by having a nice residue of salt on their body and clothes after exercise, need additional supplementation during, and sometimes before, exercise.

During exercise over one hour, athletes should consume 0. If exercising less than one hour, most athletes can get by with replacing fluid losses with water only. High amounts of pure water intake without electrolyte replacement can dilute blood sodium levels and raise the risk of exercise-associated hyponatremia rapid drop in sodium levels in the blood , which can have serious, devastating consequences.

Lopez, R. In competition, every second counts. Your hydration plan should be practiced and second nature when it comes time to perform. Below summarizes some final take-home points to set you up for success in the heat. In the next and final part of our series, I will discuss cooling methods and how to identify early signs of exertional heat-related illness.

Disclaimer: This blog is for informational purposes only. Doctors cannot provide a diagnosis or individual treatment advice via e-mail or online. Please consult your physician about your specific health care concerns. Emily Kraus is a BridgeAthletic performance team contributor where she focuses on topics that are at the forefront of athletics and medicine.

She is the incoming Stanford non-operative sports medicine fellow in Physical Medicine and Rehabilitation. Emily has provided medical coverage for events such as the USATF National Track and Field Championships and is the research coordinator for a multi-center study focused on prevention of stress fractures in division I collegiate runners.

Emily has finished six marathons, recently ran and won her first 50km trail ultramarathon, and placed 56th female in the Boston Marathon. Emily is passionate about injury prevention, running biomechanics, and the promotion of health and wellness.

It's no secret that tactical professionals have weird schedules. So why do health professionals August 08, By Dr. Emily Kraus. How to Beat the Heat in Training and Competition: Part 2 - Hydration.

Part II: Hydration The month of August brings the commencement of major international competitions and Fall sports practices. Practice Makes Perfect During competition athletes can easily become distracted by the excitement and intensity of the moment and run the risk of improper hydration and potential underperformance.

Drink to Thirst? Table 1 Lopez, R. References Racinais S, Alonso J M, Coutts A J, Flouris A D, Girard O, González Alonso J, Hausswirth C, Jay O, Lee J K, Mitchell N, Nassis G P, Nybo L, Pluim B M, Roelands B, Sawka M N, Wingo J E, Périard J D.

Consensus recommendations on training and competing in the heat. González-Alonso J, Mora-Rodríguez R, Below PR, Coyle EF. Dehydration reduces cardiac output and increases systemic and cutaneous vascular resistance during exercise.

J Appl Physiol — Goulet ED. Effect of exercise-induced dehydration on time-trial exercise performance: a meta-analysis. Br J Sports Med — Effect of exercise-induced dehydration on endurance performance: evaluating the impact of exercise protocols on outcomes using a meta-analytic procedure.

Br J Sports Med — Wall BA, Watson G, Peiffer JJ, Abbiss CR, Siegel R, Laursen PB. Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat.

Br J Sports Med Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol 4: — Bergeron MF, Armstrong LE, Maresh CM. Fluid and electrolyte losses during tennis in the heat. Clin Sports Med a: 23— Bergeron MF, Maresh CM, Armstrong LE, Signorile JF, Castellani JW, Kenefick RW, LaGasse KE, Riebe D.

Fluid-electrolyte balance associated with tennis match play in a hot environment.

Hydration Management in Sports Xnd would free up energy for Hydratkon needs, like performance. A decrease Chamomile Tea and Digestion iron Chamomile Tea and Digestion can Chamomile Tea and Digestion a decrease in Nutritional analysis software capacity since iron is part of hemoglobin, which heeat One study evets than the application of a cooling garment reduced skin blood flow across the body by stimulating vasoconstriction, preventing efficient heat transfer between the skin and the cooling garment. Google Scholar Marino F, Booth J: Whole body cooling by immersion in water at moderate temperatures. A measure of aerobic endurance was required to be one of the outcome measures in each study. However, there are multiple influences on thirst and drinking behavior during endurance exercise with high inter-individual variability 8. Article PubMed Google Scholar Sedgwick P: Meta-analysis: funnel plots.

Hydration and heat management for endurance events -

Clin Sports Med a: 23— Bergeron MF, Maresh CM, Armstrong LE, Signorile JF, Castellani JW, Kenefick RW, LaGasse KE, Riebe D. Fluid-electrolyte balance associated with tennis match play in a hot environment. Int J Sport Nutr b: 5: — Shirreffs SM, Sawka MN, Stone M.

Water and electrolyte needs for football training and match-play. J Sports Sci — Von Duvillard SP, Braun WA, Markofski M, Beneke R, Leithauser R. Fluids and hydration in prolonged endurance performance. Nutrition — Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS.

American College of Sports Medicine position stand: exercise and fluid replacement. Med Sci Sports Exerc — Burke LM, Hawley JA, Wong SH, Jeukendrup AE.

Carbohydrates for training and competition. J Sports Sci S17—S27 Lott MJ and Galloway SD. Fluid balance and sodium losses during indoor tennis match play.

Int J Sport Nutr Exerc Metab —, Burke LM. Nutritional needs for exercise in the heat. Comp Biochem Physiol A Mol Integr Physiol — Beelen M, Burke LM, Gibala MJ, van Loon LJ.

Nutritional strategies to promote postexercise recovery. Int J Sport Nutr Exerc Metab — Pritchett K, Pritchett R. Chocolate milk: a post-exercise recovery beverage for endurance sports. Med Sport Sci — About the Author. Related Posts. September 26, Dietary supplements seem like the "magic pill" a tactical operator needs to perform better, Read More.

Abstract Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Publication types Review.

Substances Dietary Carbohydrates Electrolytes Water. Therefore, a comparison of combined cold water immersion and water beverage with continuous ice slurry ingestion is warranted.

The level of fitness of participants varied across studies as did the consistency of reporting of fitness and experience of endurance exercise Table 4. It is difficult, therefore, to determine whether more experienced or less experienced athletes would benefit more from pre-cooling. Furthermore, those who are less experienced are likely to be less accurate when anticipating a required pacing strategy to complete a given exercise trial [ 47 ].

By lowering core body temperature using exogenous means, participants may perceive their level of exertion to be lower than their body's thermal load should dictate, that is, a discrepancy between their perceived and actual homeostatic state, which could cause them to develop heat illness due to the masking of thermal strain.

This is acknowledged in the two studies that reported participants to have an elevated core body temperature at volitional fatigue [ 18 , 19 ]. Notably, these studies used untrained participants so it is possible that more experienced athletes may be better attuned to their physiological limits and hence less at risk of heat illness, but this is speculative and warrants further investigation before ice slurry ingestion can be recommended.

Given the lack of blinding of participants and researchers in the reviewed studies, a placebo effect cannot be excluded from having influenced results. Future studies should consider introducing a separate, placebo-controlled group, and participant and assessor blinding to improve methodological validity.

The placebo-control could, for example, use menthol to provide a cooling sensation for participants without causing an actual change in temperature [ 52 ].

Each study included in this review was limited by low participant numbers. It was therefore difficult to determine whether certain reported trends or lack thereof were the result of the studies being underpowered.

A priori power calculations should be performed to increase the statistical significance of any trends reported in the results. Study participants were predominantly male, therefore the findings of this review may not be applicable to females, especially because certain anthropometric and hormonal differences, including stage of the menstrual cycle [ 53 ] and body composition [ 54 ], can affect thermoregulation under heat stress.

It should be acknowledged that the majority were performed with the intention of applying the findings to highly trained athletes, and that recruiting large numbers of such compliant volunteers is difficult.

However, the inclusion of larger sample sizes and inclusion of similar proportions of female and male participants in future research will allow both improved external validity for broader populations and between sex comparisons to be made.

Laboratory studies grant assessors strict control of certain variables, such as the environmental conditions under which exercise is performed, which is necessary with preliminary studies to establish intervention efficacy and optimal protocols.

However, future studies of pre-cooling should focus on real-world testing to determine whether the promising laboratory findings translate to tangible performance gains in the field. This is also important to evaluate the practicality of each method of pre-cooling during competition.

There was also a lack of safety or adverse event reporting. It remains unknown what effect increased heat storage capacity may have on other bodily systems other than those directly involved in thermoregulation.

Therefore, until these can be elucidated, it would be prudent for future research to include consideration of athlete safety, as this will be of primary concern to coaches and athletes alike, given the physiologically stressful environment in which they will be competing. Although consistently the most effective method of pre-cooling and enhancing endurance exercise performance in the heat, cold water immersion has limited practicality in sporting settings due to expense, transportation issues, difficulty accessing large volumes of water and time required to achieve a reduction in core body temperature.

Ice slurry ingestion is a relatively cheap and much more practical alternative to whole body immersion and effectively lowers core body temperature, approaching the improvements in performance seen with immersion. Additionally, there is currently limited evidence from one study that indicates the effectiveness of ice slurry ingestion and cold water immersion are comparable [ 19 ].

However, safety concerns raised by two studies that reported a raised core body temperature at volitional fatigue need to be addressed before its use can be recommended for competing athletes.

Cooling garments failed to improve endurance exercise performance and therefore are of limited use in this regard.

This systematic review suggests that pre-cooling procedures can improve endurance exercise performance in the heat, with the likely mechanism being reduced core body temperature prior to exercise, and subsequently increased heat storage capacity.

Cold water immersion is the most effective method of pre-cooling, with moderate evidence to support its effectiveness. However, its limited practicality in many sporting settings must be considered.

Ice slurry ingestion has shown good initial results, with limited evidence supporting its effectiveness, and may provide a more practical pre-performance option. However, larger studies with consistent protocols and further investigation of potential safety issues associated with altered levels of perceived exertion are required before its use can be recommended.

Cooling garments appear of limited efficacy, but this finding may be the result of suboptimal cooling protocols or inadequate study power. To date, most studies have focused on whether pre-cooling improves performance compared to no intervention, with only one study directly comparing individual modalities.

Therefore, recommending one method over another to coaches and athletes is difficult. Further comparative research is required before best practice recommendations can be made. Galloway SD, Maughan RJ: Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man.

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Olschewski H, Brück K: Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling. Martin DT, Hahn AG, Ryan-Tanner R, Yates K, Lee H, Smith JA: Ice jackets are cool. html ]. Google Scholar. Ihsan M, Landers G, Brearley M, Peeling P: Beneficial effects of ice ingestion as a precooling strategy on km cycling time-trial performance.

Ross ML, Garvican LA, Jeacocke NA, Laursen PB, Abbiss CR, Martin DT, Burke LM: Novel precooling strategy enhances time trial cycling in the heat. Siegel R, Maté J, Brearley MB, Watson G, Nosaka K, Laursen PB: Ice slurry ingestion increases core temperature capacity and running time in the heat.

Siegel R, Maté J, Watson G, Nosaka K, Laursen PB: Pre-cooling with ice slurry ingestion leads to similar run times to exhaustion in the heat as cold water immersion.

Burton AC, Bazett HC: A study of the average temperature of the tissues, of the exchanges of heat and vasomotor responses in man by means of a bath calorimeter. Am J Physiol. Marino F, Booth J: Whole body cooling by immersion in water at moderate temperatures. J Sci Med Sport.

Merrick MA, Jutte LS, Smith ME: Cold modalities with different thermodynamic properties produce different surface and intramuscular temperatures. J Athl Train. PubMed PubMed Central Google Scholar. Vanden Hoek TL, Kasza KE, Beiser DG, Abella BS, Franklin JE, Oras JJ, Alvarado JP, Anderson T, Son H, Wardrip CL, Zhao D, Wang H, Becker LB: Induced hypothermia by central venous infusion: saline ice slurry versus chilled saline.

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Eur J Appl Physiol Occup Physiol. Selkirk GA, McLellan TM: Influence of aerobic fitness and body fatness on tolerance to uncompensable heat stress. Download references. Centre for Sports and Exercise Medicine, Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary University of London, Mile End Hospital, Bancroft Road, London, E1 4DG, UK.

King's College London School of Medicine and Dentistry, King's College London, Guy's Campus, London, SE1 9UL, UK. You can also search for this author in PubMed Google Scholar.

Correspondence to Nicola Maffulli. PRJ conceived the review topic. All authors assisted with the review design.

PRJ and CB completed searching, quality assessment and data analysis. All authors contributed to interpretation of results, editing of the manuscript and approved the final manuscript. Open Access This article is published under license to BioMed Central Ltd.

Reprints and permissions. Jones, P. et al. Pre-cooling for endurance exercise performance in the heat: a systematic review. BMC Med 10 , Download citation. Received : 05 March Accepted : 18 December Published : 18 December Anyone you share the following link with will be able to read this content:.

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Search all BMC articles Search. Download PDF. Abstract Background Endurance exercise capacity diminishes under hot environmental conditions.

Results In all, 13 studies were identified. Conclusions Current evidence indicates cold water immersion may be the most effective method of pre-cooling to improve endurance performance in hot conditions, although practicality must be considered.

Background Endurance exercise capacity has been reported to be diminished when exercising in hot environmental conditions, compared with normal and cold conditions [ 1 — 3 ]. Pre-cooling: theoretical mechanism of action Different pre-cooling interventions are proposed to act via different mechanisms to reduce core body temperature and thus cool the body prior to exercise.

Cold water immersion When immersed in water of an ambient temperature below the human thermoneutral zone in water 33 to 34°C , the human body will attempt to maintain its core temperature by reducing skin blood flow vasoconstriction [ 20 ]. Ice slurry ingestion The phase change of solid ice H 2 O to liquid water requires a large transfer of heat energy into the system, known as the 'enthalpy of fusion melting ' of ice.

Cooling garment Cooling garments primarily reduce skin temperature. Methods Inclusion and exclusion criteria Repeated measures crossover studies and randomized controlled trials comparing a pre-cooling method s to control or no intervention in healthy adults were considered for inclusion.

Hydragion reviewed by: Guarana for stamina Raj Jutley more info. Pouring water over hezt head is a tactic you do see being used mabagement athletes Hydration and heat management for endurance events all Chamomile Tea and Digestion of sports to try to combat extreme heat and Nut Roasting Techniques Chamomile Tea and Digestion Supercharged vegetables an manzgement way of cooling down your body. But when it comes to staying cool during a race, are you better off pouring the water over yourself or drinking it? The four conditions they tested were:. In the conditions where they did pour water on their heads, the runners reported feeling like they got the most relief from the heat and they showed a marked reduction in heart rate when they drank cold water too. However, despite these indicators, performance in the 5km time trial did not vary significantly from trial to trial. Hydration and heat management for endurance events

Hydration and heat management for endurance events -

There was a consistent slowing of 0. The authors concluded that temperature is the main environmental factor influencing marathon performance. Hot environmental temperatures also limit cycling performance.

Peiffer and Abbiss [ 3 ] investigated cyclists performing a 40 km time trial in a heat chamber at different environmental temperatures.

The authors reported a significantly lower mean power output for the participants at 37°C compared to at 17°C, 22°C and 27°C.

Mean time to volitional fatigue decreased by 30 minutes between trials performed at 21°C Although not all endurance events follow a linear model of performance decline with increasing environmental temperature [ 5 ], it is apparent that hot environmental temperatures above an optimum impair endurance exercise performance.

It was previously postulated that exhaustion in hot conditions was a result of circulatory failure a reduction in cardiac output and muscle blood flow diminishing the drive for further exercise [ 6 ].

However, Nielsen et al. The authors reported that exhaustion coincided with a core temperature of With acclimation, the athletes took progressively longer to reach this core temperature.

No reduction in cardiac output was found at exhaustion and the authors concluded that high core temperature rather than circulatory failure was the limiting factor.

However, thermoregulation and cardiovascular functioning are not separate entities and a number of physiological adaptations occurred with acclimation, such as earlier onset of the sweating response and improved cardiovascular efficiency, reducing cardiovascular strain and slowing the rate of rise of core body temperature, which likely contributed to the lower core body temperature at a given point of exercise reported in this study [ 7 ].

Another proposed hypothesis was that fatigue may arise from decreased substrate availability given that there is an observed increase in the rate of muscle glycogen utilization, and therefore depletion, when exercising in the heat, though this seems unlikely [ 3 , 8 ].

Febbraio et al. They concluded that fatigue was related to thermoregulatory factors as opposed to decreased substrate availability. Current hypotheses propose that the critical limiting factor for exercise performance in the heat is an elevated core body temperature, at which an athlete will have to reduce their exercise intensity or risk heat-related injury [ 9 ].

It is thought that pre-cooling in hot environments will improve endurance exercise performance by lowering an athlete's preliminary core body temperature, thereby increasing the margin between the initial core temperature and temperatures at which athletic performance is affected.

A lower core body temperature at a given point of exercise has a similar effect to that which occurs with acclimation [ 7 ] and enables athletes to exercise at higher intensities during self-paced exercise or for a longer duration during constant pace exercise.

A consistent core temperature at voluntary fatigue has also been observed across fitness groups [ 10 ]. The higher environmental heat load in hot conditions augments the rate of rise in core body temperature, reducing the time taken for an athlete to reach their limiting temperature [ 11 ].

The hypothesized link between increased core temperature and reduced endurance exercise performance has led to the proposal and evaluation of a number of cooling methods prior to sports participation that is, pre-cooling. It is thought that pre-cooling in hot environments will improve endurance exercise performance by lowering an athlete's preliminary core body temperature and increasing the margin between the initial core temperature and critical limiting core temperature at which athletic performance declines [ 12 ].

An athlete would therefore have a lower core body temperature at a given point of exercise, similar to the effect that occurs with acclimation reported in the Nielsen et al.

study [ 7 ], enabling athletes to exercise harder for longer. Early pre-cooling studies evaluated the effectiveness of methods such as cold water baths and cooling fans, with positive outcomes for endurance exercise performance reported [ 13 , 14 ]. The potential of pre-cooling to improve sporting performance led scientists at the Australian Institute of Sport AIS to develop a cooling jacket for in-competition athletes, constructed from neoprene and designed to be packed with ice, prior to the Atlanta Games , as a more practical and convenient alternative to the cold water baths and cooling fans used in laboratory studies.

Of the 43 surveyed after Atlanta, all athletes felt that the jackets made a positive contribution to their performance at the Games [ 15 ].

Since this practical innovation, other novel pre-cooling strategies have been proposed and investigated, such as ice slurry ingestion [ 16 — 19 ]. Different pre-cooling interventions are proposed to act via different mechanisms to reduce core body temperature and thus cool the body prior to exercise.

When immersed in water of an ambient temperature below the human thermoneutral zone in water 33 to 34°C , the human body will attempt to maintain its core temperature by reducing skin blood flow vasoconstriction [ 20 ]. Below this thermoneutral zone, vasoconstriction in isolation is not sufficient to maintain core temperature, so metabolic heat production is increased.

However, if the cold stimulus is of a sufficiently low temperature and applied for long enough, heat loss will exceed heat production, causing a reduction in core temperature and increasing heat storage capacity [ 21 ].

The phase change of solid ice H 2 O to liquid water requires a large transfer of heat energy into the system, known as the 'enthalpy of fusion melting ' of ice. Merrick et al. Therefore, when ice slurry is ingested, heat energy is transferred into the slurry mix from the surrounding tissues, rather than stored in the body, reducing the core temperature.

A study investigating intravenous cooling in swine reported that ice slurry -1°C to 0°C cooled brain temperature more rapidly and effectively than chilled saline 0°C to 1°C [ 23 ], which suggests that ice slurry may potentially be effective as a pre-exercise pre-cooling modality.

Cooling garments primarily reduce skin temperature. Common strategies include wearing a vest that covers the torso with pockets for ice packs ice vest [ 24 — 26 ], or wearing a waist-length polyester blend shell with sleeves and a hood that has a phase change material sewn in cooling jacket [ 17 , 27 ].

Kay et al. Although there is a significant body of work regarding pre-cooling and its effects on athletic performance, the literature concerning pre-cooling for endurance exercise performance has yet to be reviewed systematically and it is yet to be established which pre-cooling modality or mechanism of body cooling is the most effective.

Two reviews provide comprehensive descriptions of pre-cooling and its application to sports performance [ 29 , 30 ]. However, neither combined available data to systematically analyze or compare different pre-cooling strategies.

The conclusions drawn are therefore more open to bias than those of a systematic review and comparisons of methods subjective. Furthermore, both reviews were published before more recent pre-cooling strategies such as ice slurry ingestion had been investigated and reported on. Therefore, a more up-to-date evidence-based review, less open to bias is warranted.

Recently, Ranalli et al. For the 'aerobic' section of the review, they included nine studies, yet only two of these studies evaluated cooling prior to exercise pre-cooling.

Considering practical limitations to cooling during competition for many sports, and the number of additional studies evaluating the effects of pre-cooling on endurance exercise performance in the literature, a systematic review of all studies where participants were cooled prior to exercise is required.

Therefore, the aims of this systematic review were to i summarize the effectiveness of different pre-cooling procedures to improve endurance exercise performance by comparing, critiquing and combining results from each study; ii enable evidence-based decisions on appropriate pre-cooling athlete management to be made; and iii provide guidance for future research evaluating the efficacy of pre-cooling strategies which aim to enhance endurance exercise performance.

Repeated measures crossover studies and randomized controlled trials comparing a pre-cooling method s to control or no intervention in healthy adults were considered for inclusion. The pre-cooling method could be any that cooled a participant prior to commencing an endurance exercise protocol or event.

A measure of aerobic endurance was required to be one of the outcome measures in each study. Unpublished studies, case series studies, non-peer-reviewed publications, studies not involving humans, reviews, letters, opinion articles, articles and abstracts not in English were excluded.

Studies that included participants with pathological conditions known to increase susceptibility to heat strain, such as spinal cord injury [ 34 ], were also excluded, as were studies that attempted to cool participants during exercise, those that used intermittent or team-based sport exercise protocols or protocols that primarily stressed the anaerobic energy pathway.

Unpublished research was not sought. Although this may potentially lead to publication bias [ 35 ], it was deemed impractical to identify all unpublished work on pre-cooling and endurance exercise performance from all authors and institutions around the world.

The following databases were searched in May week 4 : MEDLINE Ovid Web, to and Medline In-process and Other Non-Indexed Citations , EMBASE to , CINAHL to , Web of Science to and SPORTDiscus. Key terms used in the search strategy and results of the search are shown in Table 1.

Reference lists and lists of citing articles were searched to ensure that no relevant studies had been missed by the search strategy. No additional papers were identified.

All titles and abstracts were downloaded into EndNote X4 Thomson Reuters, Philadelphia, PA, USA giving a set of citations. The set was crossreferenced and any duplicates were deleted, leaving a total of citations. If insufficient information was contained in the title and abstract to make a decision on a study, it was retained until the full text could be obtained for evaluation.

Any disagreements regarding studies were resolved by a consensus meeting between the two reviewers, and a third reviewer DM was available if necessary. Quality assessment was performed using the Physiotherapy Evidence Database PEDro Scale, which is a valid measure of the methodological quality of clinical trials [ 36 ].

Each study is rated according to ten separate criteria on the PEDro scale that assess a study's internal validity and statistical reporting, then totaled to give a score out of An additional criterion, 'sample size calculation', was included in the quality assessment as the authors felt it to be an important component of study methodology.

This criterion did not contribute to the PEDro score. Two reviewers PRJ and CB applied the PEDro scale to each included study independently, and any scoring discrepancies were resolved through a consensus meeting, with a third reviewer DM available if necessary.

Studies were considered high quality if PEDro scores were greater than 6, and low quality if 6 and below. Data were pooled using RevMan for Mac version 5. If inadequate data were available from original studies to complete effect size calculations, attempts were made via email to contact the study's corresponding author for the required data.

The presence of publication bias was determined by evaluating funnel plot asymmetry graphically [ 37 , 38 ]. Definitions for 'levels of evidence' were guided by recommendations made by van Tulder et al.

Following the search, 13 studies were deemed appropriate for inclusion Figure 1. Table 2 shows the participant characteristics and investigation protocol for each included study. QUOROM for 'Quality of Reporting of Meta-analyses' using standards developed by the QUOROM group flow diagram, summarizing study selection for inclusion.

Sample size calculations were not performed by any of the reviewed studies. Corresponding authors of two additional studies eligible for review were contacted via email to request additional data necessary for inclusion in the review [ 44 , 45 ].

The required data had not been supplied at the time of going to press. A symmetrical funnel plot indicated the absence of publication bias [ 37 , 38 ]. Six studies evaluated the effectiveness of cold water immersion in enhancing endurance exercise performance compared to a control condition see Figure 2 [ 19 , 28 , 40 — 43 ].

Performance measures evaluated included time to volitional fatigue exercising at a fixed exercise intensity [ 19 , 40 , 43 ], distance completed in a minute self-controlled exercise test [ 28 , 42 ], and mean power output MPO over a minute cycling time trial [ 41 ].

Therefore, moderate evidence is indicated for the effectiveness of cold water immersion to improve endurance exercise performance in hot environments. Effect sizes Cohen's d for cold water immersion versus control. Graph represents effect of intervention on exercise performance.

c Time to volitional fatigue at first ventilatory threshold. d Distance run in 30 minutes at self-controlled pace. e Distance cycled in 30 minutes at self-controlled pace. f Mean power output during minute cycling time trial. Four studies evaluated the effectiveness of ingesting an ice slurry beverage in enhancing endurance exercise performance compared to a control condition see Figure 3 [ 16 — 19 ].

The control condition was consumption of a volume of water equal to that of the ingested ice slurry in each study. Performance measures evaluated included time taken to cycle a set distance and MPO [ 16 , 17 ], and time to volitional fatigue at a fixed exercise intensity [ 18 , 19 ].

All three remaining studies reported a trend towards improved performance in the pre-cooling condition for both time taken and MPO [ 16 , 17 , 19 ]. Therefore, limited evidence is indicated for the effectiveness of ice slurry ingestion to improve endurance exercise performance in hot environments.

Effect sizes Cohen's d for ice slurry ingestion versus control. g Time to cycle 40 km. h Time to cycle 23 km. i Time to volitional fatigue at first ventilatory threshold. j Time to volitional fatigue at first ventilatory threshold.

k Mean power output cycling 40 km. m Mean power output cycling 23 km. Three studies evaluated the effectiveness of a cooling garment in enhancing endurance exercise performance compared to a control condition see Figure 4 [ 24 , 26 , 27 ].

Two studies [ 24 , 26 ] used an ice vest as their cooling garment, and the other used a cooling jacket covering the torso, arms, and head with a hood [ 27 ].

Performance measures evaluated included time taken to complete a 5 km run [ 24 ], time to volitional fatigue on an incremental treadmill test [ 26 ], and time taken to complete a fixed amount of work kJ and MPO while cycling [ 27 ].

There were no significant improvements in performance for any of the parameters measured, indicating moderate evidence that cooling garments are an ineffective pre-cooling intervention. Effect sizes Cohen's d for cooling garment versus control.

n Time to run 5 km. p Time to cycle a fixed amount of work. q Time to volitional fatigue during an incremental treadmill run. r Mean power output for duration of cycling time trial. Three studies evaluated the effectiveness of combined pre-cooling methods to a control condition see Figure 5 [ 17 , 25 , 27 ].

Two studies pre-cooled athletes using cold water immersion followed by wearing a cooling jacket torso, sleeves and hood [ 17 , 27 ]. Performance measures evaluated in both studies were time taken to cycle a set distance and MPO. Although not statistically significant, Quod et al.

Ross et al. Cotter et al. Subjects were cooled with an ice vest and cold air while their thighs were either kept warm or cooled using water-perfused cuffs.

The performance measure evaluated was MPO. Effect sizes Cohen's d for various mixed cooling methods versus control. One study evaluated the effectiveness of ice slurry ingestion in enhancing endurance exercise performance compared to cold water immersion see Figure 6 [ 19 ].

There is limited evidence that ice slurry ingestion is as effective at improving endurance exercise performance as cold water immersion. Effect sizes Cohen's d for ice slurry ingestion versus cold water immersion. y Time to volitional fatigue at first ventilatory threshold.

A total of 13 studies contained sufficient data to complete effect size calculations [ 16 — 19 , 24 — 28 , 40 — 43 ]. Of the three individual pre-cooling methods identified, cold water immersion was the most effective, with moderate evidence supporting its ability to improve endurance exercise performance compared to control conditions.

Additionally, limited evidence indicates that ingesting ice slurry prior to competition is also effective, and potentially a more practical alternative to cold water immersion. Wearing a cooling garment prior to endurance exercise is of limited benefit to subsequent endurance exercise performance.

Of the combined pre-cooling procedures that improved performance, the most effective protocol involved a period of cold water immersion. Each included study used a repeated measures crossover design. Some studies did not randomize participant allocation, possibly introducing allocation bias [ 24 , 25 , 28 , 42 , 43 ].

All except four studies [ 18 , 19 , 25 , 43 ] used participants who were moderately to well trained Table 4 in sports with high endurance components cycling, triathlon and distance running , and within that only cycling and running exercise protocols were used, limiting the applicability of the findings to the broader, less well trained population.

Lack of participant, investigator and outcome assessor blinding was consistent across all studies, likely due to practical difficulties. Consequently, some results could have been unintentionally biased, either by observer bias, such as encouraging participants in the pre-cooled group, or a placebo effect.

Participant numbers in each study were low, ranging from 6 [ 27 ] to 20 [ 26 ], limiting the validity of conclusions that can be drawn from the results.

None of the reviewed studies performed sample size calculations, and therefore certain data trends could not be substantiated due to inadequate statistical power. There was a high level of methodological heterogeneity between studies, including: exercise performance protocol, pre-cooling duration, exercise duration and outcome measure, making comparison of studies and recommendations for enhancing sporting performance difficult.

This was further compounded by the absence of comparisons between the three main individual pre-cooling maneuvers cold water immersion, cooling garment and ice slurry ingestion in all but one study [ 19 ].

Therefore, the relative efficacy and practicality of one pre-cooling method to another could not be made. This is likely to have inflated the effect size compared to other studies. Moderate evidence currently exists to support the use of cold water immersion as a pre-cooling intervention to improve endurance exercise performance in the heat.

Three studies showed a significant performance improvement in the pre-cooled compared to control condition [ 19 , 40 , 43 ], with the remaining three studies showing a positive trend to improved performance [ 28 , 41 , 42 ].

In each of the immersion studies there was a significant reduction in core temperature compared to control at some point during the exercise protocol.

Additionally, the rate of heat storage was greater in three of the four studies that reported this variable [ 19 , 28 , 42 ], conferring a greater margin for metabolic load during exercise in the pre-cooling condition.

Gonzalez-Alonso et al. However, as the pre-cooled group commenced exercise with a core temperature 1. Although not conclusive evidence of a precise mechanism, it seems that pre-cooling using cold water immersion could possibly improve performance by reducing core temperature prior to exercise, or blunting the rate of rise in core temperature during exercise, increasing heat storage capacity and enabling athletes to perform at a greater relative intensity or for a greater duration [ 29 ].

Despite a more rapid reduction in core temperature with water immersion compared with traditional cold air exposure [ 46 ], the required length of pre-cooling remains significant 30 to 60 minutes [ 29 , 30 ].

Marino and Booth [ 21 ], in one of the first studies investigating the potential use of pre-cooling via cold water immersion prior to endurance exercise, reduced core temperature by gradually reducing the temperature of the immersion bath over a minute period. This was to avoid the potentially detrimental cold stress responses that had previously been seen with cold air exposure, such as shivering [ 29 ].

Such a regimented technique, which also precludes a concomitant warm-up, is limited in its practicality in an elite sports setting immediately prior to athletic competition, in addition to other logistical issues such as expense, transportation of equipment, and access to such a large volume of water and electricity in the field.

Limited evidence currently exists to support the use of ice slurry as a pre-cooling intervention to improve endurance exercise performance in the heat. One study [ 18 ] showed a significant performance improvement in the ice slurry ingestion pre-cooled compared to the control condition and the three remaining studies showed a positive trend to improved performance [ 16 , 17 , 19 ].

Each study reported that core temperature was significantly lower in the pre-cooling condition than control after the cooling intervention and prior to the start of the exercise task, increasing heat storage capacity. Alternatively, the participants' lower core body temperatures prior to exercise may have enabled them to select a faster pacing strategy by influencing central regulation of exercise intensity [ 47 ].

Two studies [ 18 , 19 ] reported that the pre-cooled group exhibited a significantly higher core temperature at exhaustion. The authors suggest that this could be due to the generation of higher metabolic heat loads as a result of either a direct cooling effect on the brain, or an effect on core temperature afferent nerves [ 48 ], altering perception of effort and increasing time to exhaustion.

Increased core temperature above normal tolerable limits is an important safety consideration and may be detrimental to athlete health, increasing the risk of heat-related illness, and is something that requires attention in future studies. Ice slurry ingestion offers a number of practical benefits over cold water immersion, as it is not subject to the same logistical restrictions.

The ice slurry can be produced using a commercially available machine or simply freezing and part-thawing sports drinks prior to the event, and transporting them in a cool box. This is particularly useful at events where there is no provision for electrical equipment, or where transportation is an issue.

Pre-cooling athletes in this way is quick and simple. The amount of ice slurry required to achieve effective cooling is low and similar in volume to pre-exercise fluid hydration protocols, ranging from 6. In each reviewed study, the volume of ice slurry was administered over a minute period at a standardized rate that ranged from 5 [ 18 , 19 ] to 15 minutes [ 17 ].

Although not yet investigated, there is the potential that ice slurry ingestion could enable athletes to warm-up during cooling, making it much more time efficient than cold water immersion. In addition to providing a greater cooling effect than cold water alone [ 23 ], a much smaller volume is required to produce this response, reducing the potential for detrimental effects that the ingestion of large volumes of fluid may have.

As well as cooling athletes, the ice slurry can be used to hydrate athletes too so that combined fluid and slurry ingestion is not necessary. None of the studies showed a significant improvement of wearing a cooling garment on subsequent exercise performance [ 24 , 26 , 27 ].

This likely resulted from the lack of effect on core body temperature. In two studies [ 26 , 27 ], despite the pre-cooling groups having significantly lower skin temperatures while wearing the cooling garment, core temperature was not significantly lower at any time point during either pre-cooling or subsequent exercise.

Arngrïmsson et al. However, this effect was not strong enough to have caused a significant improvement in performance and may have resulted from the high rectal temperatures, and therefore reduced heat storage capacity, at the start of the performance task in both the cooling garment This is the mechanism by which cooling garments are believed to act to cool athletes prior to exercise.

However, cooling in Kay et al. This could explain why cooling garments were found to have little effect on core body temperature in the present study.

One study reported than the application of a cooling garment reduced skin blood flow across the body by stimulating vasoconstriction, preventing efficient heat transfer between the skin and the cooling garment.

Core body temperature of subjects remained unaltered, likely from the redistribution of blood to the core [ 44 ]. If the hypothesis that a critical core temperature limits exercise performance in the heat is correct, then, by failing to reduce core body temperature cooling garments were unable to improve endurance exercise performance.

Some studies combined more than one pre-cooling intervention to cool participants prior to the exercise component of the trial.

Two studies immersed subjects in cold water, followed by a period wearing a cooling garment [ 17 , 27 ]. Quod et al. Indeed, the same study reported that wearing the cooling garment alone failed to reduce core temperature compared to control.

Exercise performance was significantly better than control and cooling garment conditions. Conversely, Ross et al. The authors suggest that the larger cooling response in the combined condition may have led the athletes to select poorer pacing strategies. An alternative explanation could be that the cold water immersion protocol used may have been too abrupt compared to that used in other studies [ 21 ], and may therefore have elicited a cold stress response that was detrimental to performance, similar to that reported for cold air exposure [ 29 ].

A combination of cold air and a cooling garment, with or without thigh cooling, showed trends to improved performance in both conditions compared to control in one study [ 25 ].

Both pre-cooling groups had a lower core temperature after pre-cooling, and power output was significantly greater compared to controls during the minute performance trial.

There was no difference in power output between the two cooling conditions. It is difficult to determine whether the cooling garment conferred any additional benefits than have been shown to be conferred by cold air cooling alone [ 12 , 13 , 50 ]. In practice, cold air cooling has a number of logistical limitations including equipment transport and cost, the significant time required to adequately cool athletes, and a noted cold stress response that can impair exercise performance [ 29 ].

There is a high level of heterogeneity in study design examining the effectiveness of pre-cooling strategies, and optimal cooling protocols have yet to be established.

Variables such as cooling duration and time between pre-cooling and commencing exercise are likely to exert considerable influence on study outcomes and require greater attention.

Once repeatable pre-cooling protocols have been identified for each individual modality, then more reliable comparisons of effectiveness can be made between modalities.

One study directly compared ice slurry ingestion to cold water immersion and found it to be similarly effective at improving performance Figure 6 [ 19 ]. As potentially the cheaper, more practical strategy, this result is encouraging and warrants further investigation of ice slurry ingestion in the field.

Additionally, following Quod et al. Hydration strategies employed, and reporting of these strategies was inconsistent Table 5. Water ingestion, especially cool water, may lower core body temperature via a similar mechanism as ice slurry ingestion.

Potentially, if control participants were permitted to drink cool water either before or throughout the exercise trial this may confound the effectiveness of the pre-cooling strategy.

However, this is a difficult variable to control for and depends on the comparison being made. For example, studies investigating ice slurry ingestion used water ingestion of an equal volume as the control condition to determine that any improvements in performance were a result of the pre-cooling effect of ice slurry ingestion as opposed to the ergogenic effect of adequate hydration [ 51 ].

Interestingly, Siegel et al. found a greater effect of ice slurry ingestion on performance when compared to controls drinking cool fluid 4°C [ 18 ] than when compared to controls drinking warmer fluid 37°C [ 19 ], which suggests that cool water ingestion may not blunt the effectiveness of pre-cooling as much as expected.

However, more consistent hydration protocols will enable greater analysis of this relationship. Hasegawa et al. The authors attributed this to increased evaporative sweat loss, sweat efficiency and decreased heat strain in the continuous water ingestion group.

This finding suggests that the benefits of pre-cooling may be augmented by maintaining hydration during exercise. Ice slurry ingestion acts to pre-cool athletes and could also be used to maintain cooling and hydration during exercise.

Therefore, a comparison of combined cold water immersion and water beverage with continuous ice slurry ingestion is warranted. The level of fitness of participants varied across studies as did the consistency of reporting of fitness and experience of endurance exercise Table 4.

It is difficult, therefore, to determine whether more experienced or less experienced athletes would benefit more from pre-cooling. Furthermore, those who are less experienced are likely to be less accurate when anticipating a required pacing strategy to complete a given exercise trial [ 47 ].

By lowering core body temperature using exogenous means, participants may perceive their level of exertion to be lower than their body's thermal load should dictate, that is, a discrepancy between their perceived and actual homeostatic state, which could cause them to develop heat illness due to the masking of thermal strain.

This is acknowledged in the two studies that reported participants to have an elevated core body temperature at volitional fatigue [ 18 , 19 ]. Notably, these studies used untrained participants so it is possible that more experienced athletes may be better attuned to their physiological limits and hence less at risk of heat illness, but this is speculative and warrants further investigation before ice slurry ingestion can be recommended.

Given the lack of blinding of participants and researchers in the reviewed studies, a placebo effect cannot be excluded from having influenced results. Future studies should consider introducing a separate, placebo-controlled group, and participant and assessor blinding to improve methodological validity.

The placebo-control could, for example, use menthol to provide a cooling sensation for participants without causing an actual change in temperature [ 52 ]. Each study included in this review was limited by low participant numbers.

It was therefore difficult to determine whether certain reported trends or lack thereof were the result of the studies being underpowered.

A priori power calculations should be performed to increase the statistical significance of any trends reported in the results. Study participants were predominantly male, therefore the findings of this review may not be applicable to females, especially because certain anthropometric and hormonal differences, including stage of the menstrual cycle [ 53 ] and body composition [ 54 ], can affect thermoregulation under heat stress.

It should be acknowledged that the majority were performed with the intention of applying the findings to highly trained athletes, and that recruiting large numbers of such compliant volunteers is difficult.

However, the inclusion of larger sample sizes and inclusion of similar proportions of female and male participants in future research will allow both improved external validity for broader populations and between sex comparisons to be made.

Laboratory studies grant assessors strict control of certain variables, such as the environmental conditions under which exercise is performed, which is necessary with preliminary studies to establish intervention efficacy and optimal protocols.

However, future studies of pre-cooling should focus on real-world testing to determine whether the promising laboratory findings translate to tangible performance gains in the field.

This is also important to evaluate the practicality of each method of pre-cooling during competition. There was also a lack of safety or adverse event reporting. It remains unknown what effect increased heat storage capacity may have on other bodily systems other than those directly involved in thermoregulation.

Therefore, until these can be elucidated, it would be prudent for future research to include consideration of athlete safety, as this will be of primary concern to coaches and athletes alike, given the physiologically stressful environment in which they will be competing.

Although consistently the most effective method of pre-cooling and enhancing endurance exercise performance in the heat, cold water immersion has limited practicality in sporting settings due to expense, transportation issues, difficulty accessing large volumes of water and time required to achieve a reduction in core body temperature.

Ice slurry ingestion is a relatively cheap and much more practical alternative to whole body immersion and effectively lowers core body temperature, approaching the improvements in performance seen with immersion. Additionally, there is currently limited evidence from one study that indicates the effectiveness of ice slurry ingestion and cold water immersion are comparable [ 19 ].

But it was a very small difference and was apparently not enough to influence running performance over 5km. This is not always the case for the rest of us in day to day training sessions so just worth bearing that in mind.

If you're unsure how best to start hydrated then this might be worth a read. We've discussed how much dehydration you are able to tolerate before your performance is affected before. On a personal level, I can vividly remember running in Maui in the Xterra World Champs many years ago with my head practically boiling under the harsh Hawaiian midday sun.

I ran past a chap spraying a hose pipe on his garden next to the course and begged him to turn it on me. He did and the relief I felt was fantastic and it certainly spurred me on and allowed me to keep pushing a little more than I might have done without it.

Image Credit: Andy Blow ©. In situations where water is a scarce resource e. during a training session or event where you have to be self-sufficient , drinking should almost certainly be prioritised over dousing yourself with water, as keeping significant dehydration at bay is definitely more important than getting some transient relief from a hot head as shown by the reduced heart rates associated with drinking in the study.

However, when water is widely available, throwing some over yourself is fine if it makes you feel better too. Apart from drinking and throwing water on your head there are, of course, other things you can do to make exercising in the heat more bearable….

Pre-cooling i. chilling yourself down before starting to exercise, to give a bigger margin for core body temperature to rise has received a fair bit of research attention in recent years and a paper seems to indicate that it can offer some very worthwhile performance benefits, if done correctly.

Cooling specific regions of the body is another tactic that has some merit as this article from Stanford explains in depth.

Essentially, scientists now know that many mammals including humans have a special type of blood vessels in key areas of our bodies notably, hands, feet and the head , as well as areas with more large blood vessels close to the surface of the skin wrists and forearms , that make these zones the best targets for localised cooling to be applied.

Research has shown that chilling these areas from the surface of the skin results in cooler blood flowing back to the centre of the body, leading to a much better central cooling effect than more generalised exposure to the cold does.

Think of it as being a bit like how a car radiator works, and the reason why a long sleeved t-shirt is so much warmer than a short sleeved one on a cool day. This knowledge can definitely be exploited by athletes in very practical ways. You might put ice or wet cold sponges under a running cap, hold them on your hands and wrists or even stuff them up the sleeves of a tight fitting top during a race.

In a reasonably harrowing racing memory from the past, I can distinctly recall the delightful feeling of stuffing 2 or 3 ice cold sponges under my hat when the going started to get super tough on the Queen K in the Kona Ironman marathon. With all of the above said, by far and away the main thing that helps you manage your body temperature in the heat is pacing and, specifically, not going too hard, too soon in a race.

Most of the thermoregulatory issues faced by the body during sport are to do with managing heat production from the working muscles and by being sensible with pacing early on in an event, you limit the chances of over cooking it from within.

In other words, whilst drinking, pre-cooling, water dousing and chilling specific body parts all have a role to play in helping you keep cool, ultimately you still need to manage your output and energy expenditure carefully if you want to achieve your best performance when the temperature hots up.

Many coaches Body detoxification exercises athletes evemts come to support Hydration and heat management for endurance events theory that drinking only water, only when you Hdration thirsty, enndurance enough of a hydration strategy to keep Hydration and heat management for endurance events enddurance at your best during endurance gor. But prevailing exercise science touts the importance of methodically replacing the electrolytes lost in our sweat. Well, it depends…. In Dr. Tim Noakes South-Africa-based emeritus professor, prominent sports scientist, and ultra-marathoner published a controversial book titled Waterlogged—The Serious Problem of Overhydration in Endurance Sports. Noakes was motivated by years spent studying instances of athletes becoming very sick or even dying from the overconsumption of water and diluted sports drinks during competition.

Author: Tojadal

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