Tag Archives: Evaporation

Hyperthermia is elevated body temperature due to failed thermoregulation that occurs when a body produces or absorbs more heat than it dissipates.  From the Wikipedia entry for hyerthermia

I had a few instances of overheating when I first got back to Malaysia.  The land where maximum temperatures year-round look like this:

Photo courtesy of Lincoln Broadcasting, Inc.

Since then I have been able to manage my core temperature.  I have been hot during rides, but not excessively so.  Where did I go wrong during the Kuantan Century Ride to end up hyperthermic?

Cartoon courtesy of Transportation Alternatives Magazine

A lot has to do with the length of this ride.  It was about 100 km / 62 mi longer than our weekend rides.  My routine for staying cool during those rides was insufficient when stretched out over 160 km / 100 mi.

There are reams of articles, blog posts and lists about how to prevent exercise-induced heat stress.  They all start with hydration.  The most important thing you can do to stave off hyperthermia is to stay hydrated.  How much fluid is required depends on body type and sweat rate.  One guideline suggests drinking 1 liter / 34 oz per hour.  By this measure I should have drunk about 6 liters / 203 oz during the ride.  I did drink about 5 liters / 170 oz.  My Camelbak Podium Chill bottles hold 620 ml / 21 oz each.  I went through 8 bottles.  So I was 2 bottles short.

What you drink is also crucial.  Lost fluids and electrolytes need to be replaced during a ride.  I added a Nuun tablet every time I refilled a bottle with water.  Even so I probably didn’t take in as many electrolytes as I should have because I didn’t drink enough.

I usually put a bottle in the freezer and another in the fridge the night before a weekend ride.  The cold fluid helps to keep my core temperature in check.  All the fluid I drank during the Kuantan Century Ride was lukewarm.  It wasn’t until I picked up some ice at the last rest stop that I got some cooling effect from what I was drinking.

I got my hydration wrong on all counts.

Clothing always gets a prominent mention.  I had on the right ‘technical fabrics’ that wick sweat away from the body.  As the sweat evaporates it carries heat away with it.

The right fabrics but perhaps the wrong color.  My jersey was navy blue, and the suggestion for staying cool is to wear a light-color.  The sun was very strong so it is likely that I absorbed more radiant energy that I would have if I had worn a white jersey.

My jersey did have a full zip.  Unzipping my jersey and getting moving air onto my bare skin helped a lot.

I also had my arms covered so they never felt hot.  My bare legs, on the other hand, did get hot.

I got my clothing partially right.

Most writers suggest pouring water over your head every 15 minutes or so.  Preferably enough to soak your jersey as well as wet your head, face and neck.  You will immediately feel that the water is cooler than your body is.  Pouring a bottle of water over my head did cross my mind, but the two times I thought about it I was at rest stops that had run out of water.

I didn’t take full advantage of evaporative cooling.

Another suggestion is to generate less body heat by riding at a slower pace.  My riding companions and I had planned to ride at an easy pace right from the start.  The intent was to conserve energy so that we would still have something in the tank for the last part of the ride.  I am sure the gentler pace helped keep my core temperature down, at least in the first half of the ride.  Of course riding at a slower speed meant spending more time in the sun than would have been the case if we had gone quicker.  I am not sure which would have been more detrimental:  generating more body heat or absorbing more radiant heat.

Let’s say that I got the pace of the ride right.

That, and having ice to eat for the final 30 km / 18 mi, is probably how I made it to the end of the ride.  I knew I was feeling the effects of hyperthermia with 50 km / 31 mi to go.  I was light-headed, which I now know is an early symptom of heat syncope.  I started cramping on the run in to the finish.  That is another symptom of hyperthermia.

After the ride I spent 30 minutes sprawled in the shade, shoes off and iced drink in hand.  That cool tiled floor felt good.

Photo courtesy of Wai Leng Mann

So what to during the 120 km / 74.5 mi Iskandar Johor Mega Ride in July?  The lessons learned from the Kuantan Century Ride are:

1. Freeze two bottles and chill the third.  Carry one frozen bottle in the middle pocket of my jersey, where it can cool my lower back.
2. Drink a liter of Nuun-infused water an hour.
3. Carry extra Nuun tablets.
4. Buy chilled water at petrol stations rather than depend on rest stops.
5. Soak my head and jersey with water every 30 minutes or so.
6. Wear a light-colored jersey.
7. Ride at a gentle pace.

All the “Beat the Heat” articles I read today have given me a few other things to try as well:

1. “Pre-cool” 30 minutes before the start by drinking cold fluids.
2. Wrap a water-soaked bandanna around my neck.  Or go one step further and wrap an ice-filled sock around my neck, as suggested by Phil O’Reilly, former president of the Five Borough Bike Club.
3. Buy ice cream at petrol stations.

I’ll give these other suggestions a miss for now:

Cartoon courtesy of Transportation Alternatives Magazine