Heat Fatigue

[Too Tall]

Today might be the first time I ever 100% succumbed to heat. Heat and humidity are things I tolerate well generally speaking. I do all the "smart" things to waylay ill effects yet today after about 1 hr. of race pace riding I lost it in the middle of a hill. My body felt the same as it always does during hard efforts a balance of aerobic capacity and lactate buildup/lactate clearing blah blah. But this was different, the steam went out of my body and could barely pedal. It took ages to recover, my pals were waiting to make sure I was ok but had to cut it short and go find a cold coke :(

What experience do you bums have with this?

[mzilliox]

None yet, but i fear it today. temps pushing 97 today and my buddy wants to do a metric with 5k ft climbing. im a bit nervous with the heat. Wish me luck. i find the heat to be sapping on a daily basis while i farm. much easier to work in spring and fall.

[joosttx]

Today might be the first time I ever 100% succumbed to heat. Heat and humidity are things I tolerate well generally speaking. I do all the "smart" things to waylay ill effects yet today after about 1 hr. of race pace riding I lost it in the middle of a hill. My body felt the same as it always does during hard efforts a balance of aerobic capacity and lactate buildup/lactate clearing blah blah. But this was different, the steam went out of my body and could barely pedal. It took ages to recover, my pals were waiting to make sure I was ok but had to cut it short and go find a cold coke :(

What experience do you bums have with this?

I did a 100 mile ride on the 4th of July a few year back in Philly. I remeber looking at the temp on the garmin and it reading 124F on the pavement towards the end when we were out of water. I couldnt pedal and couldnt really breathe well-- this is kid from Texas whose Mom would make him play all day outside in the summer time, who mowed 15 lawns a week in the Texas summers in Highschool. I came close to something really bad. For about 5 years after that ride, anytime it got hot my heart rate jumped quickly and I felt the effect of heat faster than I use to- what you described in various levels of exterme. Now I dont. I assumed my body governer lowered at bit since it couldnt trust my conscience self to make good decisions.

[DaveS]

I did a hot ~80 mile race in the Blue Ridge region of NC when I was a grad student. Felt great for the first 2.5 hours, don't remember the next hour very well, crossed the line and passed out when all the blood pooled in my legs. Ended up in the local ER with some minor acute kidney failure for IV fluids.

Today I cut my ride a little short and increased water intake and rest between tempo intervals. Not worth risking it again!

Dave

[Too Tall]

I did a hot ~80 mile race in the Blue Ridge region of NC when I was a grad student. Felt great for the first 2.5 hours, don't remember the next hour very well, crossed the line and passed out when all the blood pooled in my legs. Ended up in the local ER with some minor acute kidney failure for IV fluids.

Today I cut my ride a little short and increased water intake and rest between tempo intervals. Not worth risking it again!

Dave

Interesting reading everyone's reports. I'm still not right. Comments regarding one bad episode affecting future outcomes unfortunately rings a bell. When we were training for Ultras there were times went dug too deep and paid a price.

[DaveS]

Interesting reading everyone's reports. I'm still not right. Comments regarding one bad episode affecting future outcomes unfortunately rings a bell. When we were training for Ultras there were times went dug too deep and paid a price.

The ER doc suggested that if I ever felt on the brink again, to drink 1-1.5L of cold pedialyte and lots of sleep. Might be worth giving it a shot....

DaveS

[tiretracks]

First post. The effects of heat stress are cumulative, making future episodes both worse and easier to succumb to.

[Too Tall]

First post. The effects of heat stress are cumulative, making future episodes both worse and easier to succumb to.

Thanks for the observation. It's not fair man, not fair. I'll have to up my stealth and cunning game.

[ericpmoss]

^ What they said. In 2006 I did a 100 mile ride without knowing there was a heat warning -- Nebraska in July always sucks, so it seemed normal. 106F in the shade, 130+ on the blacktop. Flatted and limped home. Every muscle cramped, head to toe. I can no longer be in 90F heat without getting dizzy and having to steady myself. Sucks sucks sucks.

[bigbill]

This has been the hottest week of the year so far with heat indexes around 110 each afternoon. I've ridden about 210 miles including a ride this morning that was absolutely awful. I thought I could beat the heat by heading out at 7am but it was already in the 80's with humidity in the 80's. It only got marginally better as the temps rose and the humidity lowered towards 60%. I had emptied both bottles about 7 miles from home so I stopped at a convenience store and filled a bottle with ice and coke. That got me home with 34 miles. Sometimes I ride with a camelbak this time of year, but I find that it's a tradeoff between carrying more water and being hotter because I'm wearing it. I may wear it tomorrow since it's like carrying two extra bottles.

I grew up in this part of Texas, worked on a farm, mowed yards, lived in a house without A/C that relied on an attic fan at night, I was pretty much heat proof. As an adult I did multiple deployments to the Middle East and SW Asia, I've seen epic heat. When I first moved back here after I retired, I had a hard time with the heat. As the years progressed, it got better, but this week has kicked my ass. My countermeasure is to ride east-west so the predominate south wind is crossing me and planning my routes so I have places to fill my bottles. I keep two 32oz Nalgenes in the fridge filled with water. After a ride, I'll either dump a scoop of drink mix or a NUUN tablet in the bottle and drink it with dinner. Another thing I do is weigh myself before a ride and then after to know how much fluid weight I lost. Chronic dehydration is the thing that affects me most so I keep an eye on weight. The heat warnings were supposed to end tonight but they've extended them another day, at least.

[Too Tall]

Weighing myself before/after is really good advice.
Bill, you made me remember one epic Sonoran Desert crossing. We dropped like a rock from the mtns. and cool temps into this easy bake oven. The heat reflected from the road was astounding. We took to filling socks with ice and tying them around our necks...which lasted all of 15 mins. but heck any relief was something.
I'm bothered that lack of tolerance to heat might be cumulative.

[bigbill]

Weighing myself before/after is really good advice.
Bill, you made me remember one epic Sonoran Desert crossing. We dropped like a rock from the mtns. and cool temps into this easy bake oven. The heat reflected from the road was astounding. We took to filling socks with ice and tying them around our necks...which lasted all of 15 mins. but heck any relief was something.
I'm bothered that lack of tolerance to heat might be cumulative.

For me, it's about my body's ability to cool. When it's really humid, my jersey and shorts soak with sweat and don't evaporate, I just drip sweat. It holds the heat in and it accelerates my fluid loss. If I can limit how much I dehydrate, I'm ok for about two hours in 100+ heat index.

Last month I was in the Grand Canyon for 8 days. Most days were over 110 degrees and one day was 130. The National Park shut down hiking trails but we were in a raft going down the Colorado River so we were unaffected. It was bearable because humidity was <10% most of the time. I could sweat and it would evaporate. I was drinking around 2 gallons of water a day but I was always a little dehydrated but not bad. When I do my AZ bike trip each March, I have to be on the road by 8am to get 40-50 miles before it gets too hot. Radiant heat with low humidity is still hot.

[robin3mj]

Reminds me of a ride I did from Arlington Courthouse about 8-9 years ago. Rode to some spot on the C&O, out to Whites Ferrry and back. Got to Key Bridge Marriott completely unable to function. Literally 2 miles from home. Wife graciously picked me up and I spent the rest of the day on the couch shivering and running to puke. Did not seek medical attention but probably should have. Took me a solid week to get right again.

No cumulative effects really, but anytime I'll be out for 10mi or more (which includes my current commute) and it's hotter than normal, I will bring a bottle. These last few weeks I have been mainlining ice water all night at home and all day on weekends. Just to stay on ahead of it.

[dashDustin]

Lots of experience riding in the heat. To me it sounds like 1) your body was already fatigued, and 2) your body wasn't prepared (beyond the fatigue...nutrition, hydration). I don't think there's anything you could've done on this ride to prevent what happened, other than completely change the ride dynamic. For myself, the big red flag is my inability to control heart rate...meaning, it spikes badly. That's when I know I'm on the brink and that's when I bring it down, becoming more concerned with conserving. You cross that line once and you won't forget it. It's a god awful feeling and sticks around. My last one was in 2011. I stopped at 3 gas stations in 5 miles, taking breaks at each one.

[Pinned]

This is something that worries me, and while I haven't had any issues myself I did have a bit of a scare with a friend on a recent ride. It was about 55 miles w/ 4500' of climbing - somewhere in the middle of the biggest climb it hit 105*. We stopped and he was acting pretty wonky, gave him what I had left for water - we ended up stopping a number of times on the rest of the climb and he walked a bit. He was really hurting, and that was enough to scare me as we're pretty similar in terms of riding ability.

Once I checked out what we'd eaten it was clear neither of us ate enough, and we should have stopped for more water. Everything feels good until it goes horribly sideways, I have to make a conscious effort to eat and drink on the bike.

[11.4]

TT, you may be taking "lack of tolerance being cumulative" in the wrong context. It does take more than 24 hours to recover for many people, which means one bad day shows up the next day as well. But it doesn't mean a progressive decline as long as you give yourself recovery time.

Heat disorder really is a combination of perhaps four different issues: First is simple dehydration, which is easiest to replenish but can still be slow to recover. Your kidneys and vascular system don't immediately pop back, and it only takes a percentage or two of water depletion to cause problems that themselves can take a couple days or longer to heal.

Second is actual hyperthermia at the organic level. That's a body that's working out for hours, generating heat, absorbing heat from a blazing sun, and operating in an atmosphere where there's little cooling opportunity due to humidity and to a heat imbalance with the body (as soon as the ambient temperatures are near or over core body temperature, heat transfer starts to become limited. Organic hyperthermia is what is most often the culprit when you have slow recovery.

Third is vascular dysfunction. Remember that photo of a TdeF rider a few days ago with the incredibly vascularized legs? Your body tends to do the same, expanding the diameter of blood vessels and lowering pressure to ease circulation. It causes the changes in the blood's ability to carry oxygen and to carry away metabolites and CO2, and it physically reduces the pumping efficiency of the veins in the legs. This recovers fairly quickly, but it leaves some problems behind. It increases the tendency to throw clots, develop small pulmonary embolisms, and the like.

Last is specific organic dysfunction. We don't think of a temperature elevation of only a half a degree or degree to be significant, but in survival medicine you learn that incredibly small increments can have a huge effect on actual survival, much less athletic performance. Core temperature changes cause reactions in several organs, such as the liver and pancreas, and it also signals changes in electrical performance in the heart, leading to potential for AFib and related myeloelectric disorders.

A typical fit cyclist isn't going to be crippled by all four of these issues. Typically you'll be sensitive to one type and handle others quite well, so it pays to figure out just what's going on with you. Being told to drink a lot and stay in air conditioning doesn't really help a lot. I'd suggest that if you have another episode, you want to get some basic bloodwork done as quickly as possible, plus have the equipment to monitor blood pressure, pulse, blood sugar, etc. so you can take recordings every four hours or so after an event where you've been affected. You can buy digital blood pressure monitors and blood sugar testers very inexpensively and have them in your racing bag. They can tell you whether you can safely race the next day, or whether you are deteriorating and need to make it into an emergency room, etc. Most importantly, this kind of self-observation and analysis lets you identify what you are most prone to so you can know whether you needed physical cooling (like a support hose filled with ice tied in the back of your neck) or increased water intake, or altered sugar intake during the event, and so on. Until then, you're operating blind. As I mentioned above, heat can upset your blood sugar regulatory feedback system, so you sometimes can solve heat fatigue by reducing sugar intake or other simple measures. If you have any blood sugar effects, I'd immediately get a blood glucose tolerance test done to make sure your system is functioning properly and you aren't pre-diabetic. But to do any of this, you need to collect information on your own body's performance first.

The human body can adapt to extreme heat if you're smart about it. If you determine what the heat is doing to you, you can correct the effects. That's the healthy and most race worthy approach to take to heat fatigue. Just taking some glib step such as drinking more won't tell you what really happened. This goes beyond race performance as well; it helps you build your physiological fitness so you have much greater heat stability, which is a long-term benefit for cycling and also for simple existence in hot weather.

[Bewheels]

^^^
Wow!
Where is the "answer of the thread" button...

[Too Tall]

Lots of experience riding in the heat. To me it sounds like 1) your body was already fatigued, and 2) your body wasn't prepared (beyond the fatigue...nutrition, hydration). I don't think there's anything you could've done on this ride to prevent what happened, other than completely change the ride dynamic. For myself, the big red flag is my inability to control heart rate...meaning, it spikes badly. That's when I know I'm on the brink and that's when I bring it down, becoming more concerned with conserving. You cross that line once and you won't forget it. It's a god awful feeling and sticks around. My last one was in 2011. I stopped at 3 gas stations in 5 miles, taking breaks at each one.

I think you've captured what happened to me. I'm not too bright sometimes.

Good stuff Lane. I know much of what you are saying. In spite of myself I managed to do this ;) Probably the one most important thing I managed to ignore was prior fatigue, I've been logging alot of hard rides. Also, heart rate which I completely ignored during the ride.
FWIIW A digital blood pressure cuff and me are good friends.

[joosttx]

An interesting experiment to do with a HR monitor and bottle of cold water is will you are super hot put a bottle of cold water on the inside of your wrists while watching your heart rate. Your HR will drop instantly 5 bpm.

[Tamu8104]

Similar to Dustin, lots of experience riding in the heat. Had one episode back when I was racing during a July race where I got so hot I started getting chills and goosebumps. Tried to push through but body quit, heart rate spiked and no power. Last race I did in TX between May and Sept... Now my summer are primarily base miles and I try to stay away from high intensity.