This heat related follow up question came in James K.:
Some of us runners, especially of the trail running and ultra-running sort, actually have significant portions of our race seasons in the hotter climates and/or hotter months, so for us, heat acclimation becomes a necessity. A great example, of course would be last weekend’s Western States 100. Of course, trail/ultra running is still a niche, and WS, for instance only includes about 350 entrants, we’re still a big (and growing) part of running. Could you discuss heat acclimation and heat management strategies.
I think this is applicable to more than just ultra runners. Anyone running any distance needs to acclimate to heat if that is what they are going to be racing and/or training in heat. They also need appropriate heat management strategies.
There are three elements that really need to be addressed: hydration, electrolyte balance and body heat management.
Given that – I want to underscore the most important element in this whole discussion. That is the maintenance of moderate body temperatures. Secondary in importance is the loss of electrolytes and fluids. Of course there is an interplay (sweat loses both water and electrolytes). However, your body temperatures can rise to unhealthy levels without having any electrolyte imbalances or dehydration. And it is far less likely that you will solely have an electrolyte imbalance by itself – it is usually in conjunction with excess fluid loss as well.
[The exception is hyponatremia which is the result of OVER hydrating with water which causes the electrolyte imbalance. These people are not dehydrated… they are very well hydrated. However, to put this in perspective it is actually rare novice, female and slower distance runners tend to be more prone to this condition (well above four hour marathoners for instance).]
It requires up to 3 weeks to acclimate to heat conditions. And you’ll start to lose those accommodations within only 4 days. Acclimating does not mean it’ll feel cooler to you than a non-acclimated person necessarily. But, it will make your body function more efficiently in the heat.
You acclimate by working out in the conditions that you will be racing in. There was at least one research study I remember that indicated acclimating to high heat under dry conditions is not the same as high heat and humid conditions. Regular exercise doses over weeks will get you acclimated.
Tidbit: 5% body weight loss = 10% decrease in performance
Your goal is to keep your losses to less than 3% of your body weight.
Hot weather marathoners should know how much weight they lose per hour. One quart is about 2 pounds. Weigh yourself naked before a hot run. Weigh yourself naked after a hot run. Now you can calculate how much fluid you lose in a given time span under those weather conditions. (If you took in fluids during the run you’ll have to factor that in.)
Fluid replenishment is also critical for glycogen (your primary source of energy) use in muscles. Get low on fluids and it also impacts your muscle’s ability to get and use glycogen! You run out of energy! Use drinks of only 6-8% carbohydrate concentrations. There are hypertonic (much higher concentrations) drinks but you must avoid these. they adversely effect water absorption as do the various gels, shots and gu’s. In an ultramarathon you need nutrition sources however and fluids is the best way to get them since you also get the fluid intake simultaneously. Just remember that your stomach coudl be full of fluid and tons of carbs but they do you no good if they remain in your stomach and are not absorbed in the rest of your body.
Fluid replenishment is very individual just as fluid/electrolyte loss is individual. Be sure you like the flavor of your drink. It doesn’t matter what the advertising says if you don’t like it you most likely will not drink as much. What good is a “great” drink going to do for you remaining in your Camelpak? Experimentation is critical all during your training to fine tune YOUR unique needs for race day. Not knowing this in advance or just playing it by ear on race day will spell disaster.
Techno and Non-Techno Heat Management
Factoid: 98.6F (37C) = normal body temperature; 106F (41C) = cell damage occurs; 107.6F (42C) = protein coagulates – cells die… and usually so will you. It has been clearly demonstrated in controlled laboratories that 52F (11C) to 70F (21C) and 88F (31C) yield progressive decrements in performance.
How serious is body temperatures taken at elite levels? US Olympic marathoners wore cooling vests right up to the start of the race in order to keep their core body temperatures down. The vests have been shown effective in doing so. They delay the inevitable rise in body temperatures. (In fact many US Olympic outdoor teams and sports used these last year.)
New clothing has been developed that is promising in body heat regulation. One manufacturer (X-Bionic) appears to have some research data supporting its clothing line’s efficacy in handling heat. I’ve read some pretty interesting stuff on this clothing. It was even featured on Sports Science – the Fox TV program. Worth a look… but pricey!
White clothing indeed has been shown to reduce some heat retention over black clothing in studies conducted in Yuma, AZ.
Dousing one’s head allows for subjective cooling (it feels good) but has not been shown to have any effect on body temperatures.
Scrubbing with a sponge may actually lend assistance in body temperature maintenance. By keeping pores unclogged with oils it allows free flowing sweat which yields a cooling effect.
Get in the shade when possible. (Desert dwellers might have an issue with this one.) It can be 10F or more degrees cooler in the shaded areas.
And finally how’s this one? As crazy as it seems there has been research that supports cooling hands (palms specifically) has a positive effect in prolonging the ability to perform longer in the heat. So, try it out… have your race pit crew hand you some ice to hold onto.