Summer is here and the temperatures are rising…fast. In some parts of the country, like Texas, Florida…and in California, the temperatures soar above 100!. For most people, the worry is there: “how can I handle the heat and still race well?” Staying on top of your hydration is essential!
Body water: Your Natural Coolant
Remember that body water is your effective means of dissipating heat- the blood circulates to the muscles to bring fuel and at the same time, picks up metabolic -by-products one of which is heat produced through muscular contraction. Blood then circulates to the skin to offload the heat through several mechanisms, the most effective, being evaporative cooling- aka sweating!
As you sweat, you lose water from the blood, (and as the plasma volume drops, the body pulls water from other spaces to try to keep blood volume up); if you are slack on your hydration, you compromise your blood volume- thus blood circulation to the muscles, the skin, and water for sweating.
Add salt tablets? Think again!
“Ok, okay! I’m using Preload and Active, I think I’ve got my hydration under control… what about salt tablets…?” (I get this question a lot in early season..). No you do not need salt tablets! Even as a “salty sweater” the preload+active+sodium from the foods you are eating is plenty of sodium; salt tablets contribute more stress to the GI than most people realize. The chloride ion of sodium chloride; while necessary for cellular function and is also lost through sweat, is not lost at rates high enough to warrant high load replacement during exercise. The chloride ion interferes with what we call the membrane potential of the intestinal cells, allowing the spaces between the cells to “open up”, releasing endotoxins, causing an abnormal water flux and severe diarrhea.
What can I do on course to help keep me cool?”
Before you start the race you can do a few things to “pre-cool”, effectively reducing the core temperature at the start of the race, so you have a longer time to reach a critical core temperature (i.e. fatigue).
Strategies/Methods for Pre-Cooling/Cooling:
1) Whole body cooling through full body immersion in a thin drysuit with water perfusion or swimming in cold water for 10-15 min. This method drops core temperature and skin temperature; reducing perceived thermal strain during subsequent exercise.
2) Icy drinks(Have a PreLoad slushy!)- Compared to cold water, icy/slushy fluid ingestion lowers pre-exercise core temperature which increases time to exhaustion and allows a greater core temperature to be achieved at exhaustion.
3) Water perfused vest with circulating cool water, not an Ice Vest (ice on the skin is too cold, this will cause a vasoconstriction response, forcing hot blood from the skin back to the core, driving UP the core temperature). This cooling method also maintains cerebral blood flow more effectively than without skin cooling.
In an ideal situation you’d be slurping down ice cold Active and sucking on cold popsicles throughout the race…. But practical isn’t the ideal.
Anything you CAN ingest that is cold will help reduce the rate of core temperature rise- grab some ice water from an aid station and drink it down; suck on the ice- but DO NOT pour ice water on your head! (The ice water is too cold, the head is very vascular thus the cold of the ice will constrict those vessels, sending hot blood back to the core… COOL water is fine, it is a gradient thing… cool water will help pull heat away as if you were sweating buckets.). Cool water on the forearms is also a great heat offloader- using UV protectant armskins to prevent sunburn and to hold cool water against the forearm will help keep core temperature rise at a lower rate.
Photo Credit: Lyne Lamoureux
Above all else, keep drinking! Often, and start early- sip sip nibble nibble. As cold as you can get on course, but not against the skin.
Hot, but doable. Race well, race hard, and have fun!