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Old 07-07-12, 09:42 AM   #1
Road Fan
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Was that heat exhaustion?

How variable are the symptoms of heat exhaustion? Does everyone get the same symptoms, or do some of us only get a few?

I'm nearly 59. Yesterday I was out on a 35 mile ride in central Michigan, and toward the end the temp had to be near 100 if not above. The ride was challenging, but toward the end I saw my HR between 150 and 160, with no sensation of being near the edge or any unusual symptoms other than that reading. I had drunk three large bottles of water, ate a gel mid-ride, and tried to moderate my effort when I noticed the high HR. Two miles before the ride end I dialed it back to about 8 mph/low cadence to initiate a cool-down before getting into the heat-soaked car, and HR decline was very slow. Earlier in a ride or

5 years ago my LT measured at around 162 (MAXHR seen in the same test was around 195, but I cant' say that was actually my maximum), but I really don't know what it is today. On many cooler days I feel quite stressed when I see 160 on the HRM.

Was that heat exhaustion? The only one of the standard symptoms was the high HR.

I ate the gel about 30 minutes before noticing the high HR. Could my electrolytes have been ok, and the high HR strictly a sign of dehydration despite the 2.5 large bottles I drank?

Last edited by Road Fan; 07-07-12 at 11:32 AM.
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Old 07-07-12, 10:24 AM   #2
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High HR is dehydration, which can be the start of heat exhaustion. What I notice as symptoms of coming heat exhaustion, besides the high HR, is that my forearms dry up instead of being covered with a light sweat, and even small efforts are taxing - I'm off the back. When I notice that, I'm probably 20 minutes from being in in clinical heat exhaustion and better find water/shade/AC within that time radius. If I have water with me, just sitting in the shade for 15-20 minutes and probably drinking all the water I have will get me back on the road, but I had better find more water soon.

In hot weather, it's frequently impossible to keep up with water loss by drinking. Heat training helps quite a bit, as does training and experimenting in drinking max quantities of water. Most folks are limited to about a bottle/hour, but water loss can be 3 liters/hour while riding. See:

http://www.cptips.com/fluids.htm
http://www.hammernutrition.com/knowl...wledge-section
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Old 07-07-12, 03:47 PM   #3
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In the absence of other symptoms of heat exhaustion (dizziness, cool/pale skin, profuse perspiration, headache, nausea...), the rapid HR could be the result of the muscles having to work harder in hot temperatures ---- or, it could be an early (or only) sign of heat exhaustion and from there it's a slippery slope to heat stroke if one doesn't take immediate measures to cool down and hydrate.

In any case, during activity in hot temps it's best to assume it could be the worst and take immediate measures to get into a cool shady spot, take cooling measures, and rehydrate.

When your skin goes from moist to dry, that's could be a warning sign you're headed for heat stroke, a medical emergency.

http://www.webmd.com/a-to-z-guides/heat-exhaustion

http://www.webmd.com/a-to-z-guides/heat-stroke
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Old 07-07-12, 04:12 PM   #4
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Originally Posted by Yen View Post
In the absence of other symptoms of heat exhaustion (dizziness, cool/pale skin, profuse perspiration, headache, nausea...), the rapid HR could be the result of the muscles having to work harder in hot temperatures ---- or, it could be an early (or only) sign of heat exhaustion and from there it's a slippery slope to heat stroke if one doesn't take immediate measures to cool down and hydrate.

In any case, during activity in hot temps it's best to assume it could be the worst and take immediate measures to get into a cool shady spot, take cooling measures, and rehydrate.

When your skin goes from moist to dry, that's could be a warning sign you're headed for heat stroke, a medical emergency.

http://www.webmd.com/a-to-z-guides/heat-exhaustion

http://www.webmd.com/a-to-z-guides/heat-stroke
Thanks for those links. Many of us, including me, use "heat exhaustion" incorrectly. That said, I've seen riders heading into heat stroke, but never saw a rider in heat exhaustion as described in that link. I did once find a hiker in heat exhaustion and finally persuaded him to drink all his water and take off his down jacket. He was perspiring heavily but felt cold.

But probably we go through heat exhaustion without really noticing it, since perspiration helps cool us, and we know our performance will suffer in the heat. Which is dangerous. I almost had to put my wife in a river once. Close one.

We have a hot weather pass climb scheduled for tomorrow. No water on the climb. We'll take Camelbaks and food bottles, wear bright yellow jerseys (we don't own white), and stay aware. We'll be climbing into snow, so plenty of cooling opportunities up top!
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Old 07-07-12, 04:19 PM   #5
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I believe the term heat exhaustion actually means the body is exhausting its efforts to reduce the core body temperature --- not the feeling of "exhaustion" or fatigue while exercise.

Take care tomorrow and start hydrating today and early tomorrow morning before your ride.
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Old 07-07-12, 06:10 PM   #6
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I believe the term heat exhaustion actually means the body is exhausting its efforts to reduce the core body temperature --- not the feeling of "exhaustion" or fatigue while exercise.

Take care tomorrow and start hydrating today and early tomorrow morning before your ride.
Thanks. I drank 2 bottles of HEED today, then we'll each have a 20 oz. breakfast drink 2 hours before the ride, then split a quart of water with my wife while we're sorting out the bike and our clothes at the ride start, taking a couple of Endurolytes with it. We'll be religious with the Endurolytes during, 1-2/hr. That's our normal hot weather routine. We'll be fine.
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Old 07-07-12, 07:32 PM   #7
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Ok, so the Mayo Clinic site lists the following possible sysmptoms for heat exhaustion, and whether I had them:

Cool, moist skin -- no
heavy sweating -- yes
faintness -- no
dizziness -- no
fatigue -- no
weak, rapid pulse -- rapid, but I don't know if it was weak
low BP upon standing -- don't know
muscle cramps -- no
nausea -- no
headache -- no

It's not at all clear that I had heat exhaustion rather than dehydration. In any case, drinking, eating something salty, and cooling off helped it and today I feel fine.
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Old 07-07-12, 07:34 PM   #8
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Quote:
Originally Posted by Yen View Post
In the absence of other symptoms of heat exhaustion (dizziness, cool/pale skin, profuse perspiration, headache, nausea...), the rapid HR could be the result of the muscles having to work harder in hot temperatures ---- or, it could be an early (or only) sign of heat exhaustion and from there it's a slippery slope to heat stroke if one doesn't take immediate measures to cool down and hydrate.

In any case, during activity in hot temps it's best to assume it could be the worst and take immediate measures to get into a cool shady spot, take cooling measures, and rehydrate.

When your skin goes from moist to dry, that's could be a warning sign you're headed for heat stroke, a medical emergency.

http://www.webmd.com/a-to-z-guides/heat-exhaustion

http://www.webmd.com/a-to-z-guides/heat-stroke
Yen, you sound nurse-like.
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Old 07-08-12, 10:40 AM   #9
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In another life, I was nurse-like. Now I'm a member of a volunteer search and rescue team; heat/cold-related illness is one of the things we recently covered. I studied heat exhaustion/stroke many times because I always wondered what they mean, what they look like, and how they are different. Heat stroke is the most serious, a medical emergency that can lead to death and requires medical intervention at the hospital.
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Old 07-08-12, 12:22 PM   #10
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We had a rider on Wed (temps in low 90's by time we finished, high humidity, sunny) on a 40 mile bike ride who started having severe leg cramps an hour or two after the ride was finished and after eating lunch. We were still in the restaurant when she was suddenly in severe pain, couldn't stand, walk, was yelling at times in pain. We pulled out every cramp remedy we could think of: bottles of Powerade, packets of mustard, even got the kitchen to give us some vinegar and honey (someone googled that one). Nothing helped. She finally okayed us calling 911, but then thought she was getting better and said not to. These cramps went on for a good two hours intermittently. We finally were able to get her to an urgent care (tricky, since she still could not walk) and get some iv fluids. Halfway through the bag, she was a new person and no more problem.

She had two bottles of water and one bottle of Gatorade on the ride as well as one energy bar of some kind. Said she ate breakfast (don't know what) and had a good lunch after the ride. She has been on the Atkins diet for a while now, which I understand can lead to cramping after exercise. A friend with EMS training said we should have called 911 after the first 15 minutes of cramps when they did not get better and that it was a sign of heat exhaustion (or stroke? - don't know which). Is this true?
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Old 07-08-12, 09:06 PM   #11
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Usually this is just overwork, but overwork cramps usually go away in about 15 minutes. Probably they gave her saline, which would indicate the problem as being seriously down on electrolytes. Note that the more Gatorade one drinks, the worse one gets. So it's no help at all in the electrolyte department. So that's probably it, on top of the overwork thing. A lot of people got suckered into the low salt diet fad and that could be a contributor.

The only thing that's proven to help, outside of IVs, is the 500mg size of Tums. For unknown reasons that works like a charm, in seconds. The 750mg size does not work, again unknown reasons. I've found that immediate after-ride ingestion of just one 500mg/250mg cal/mag capsule solves after-ride cramping for most people. It's quite common, really.

On organized rides, I've come across people who've been writhing in the ditch for quite some time. I haven't seen one that Endurolytes, water, and Tums didn't get back on the road.

Probably nothing to do with heat exhaustion/stroke, just a screwed up metabolism.

Edit: I wasn't satisfied with this post because some excellent research has been done showing no relation between cramping and electrolyte and hydration levels. I looked around some more and found these conflicting articles:
http://www.coolrunning.co.nz/articles/2000a006.html
http://www.sportsinjurybulletin.com/...thon-cramp.htm

The most interesting paragraph for this sub-question might be this one from the first link:
Quote:
Another theory is that they result from burning protein for fuel in the absence of readily available carbohydrate. In fact, one study supports such a notion. In this research, muscle cramps occurred in subjects who reached the highest levels of ammonia release during exercise. High ammonia levels indicate that protein is being used to fuel the muscles during exercise. This may indicate a need for greater carbohydrate stores before, and replacement of those stores during intense and long-lasting exercise.

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