When is it heat exhaustion vs. silent heart attack?
February 23, 2021 1:54 PM   Subscribe

Several times in my life when I've been working or exercising in the heat (or even the cold!) I push myself too hard and my body retaliates. No pain no gain, but when should I worry?

When this has happened, sometimes I'm flat on the ground breathing heavily, sometimes I'm in the gym bathroom vomiting, sometimes I just have to sit in a chair and think nice thoughts until it passes. It hasn't happened that often, less than a dozen times I can remember. Cycling is the most frequent trigger. The feeling usually passes after 1/2 hour or so.

The last such incident was surprising, because I had been moving heavy boxes all day but wasn't really pushing a lot of BPM. There was no pain, just fatigue and a feeling of unwellness. I just thought "wow, I'm getting old" and drank water until it passed. So I'm wondering -- how do you tell a silent heart attack from heat-related or activity-related exhaustion?

I have no discomfort with moderate exercise, and a recent heart checkup including ECG showed nothing abnormal. Should I worry about diagnosing the past, or just try to treat my heart as well as I can in the future? And when I'm in my fifties and push myself too hard again, how will I know whether to go to the ER or wait it out?
posted by RobotVoodooPower to Health & Fitness (7 answers total)
Best answer: I wonder if you're describing what us cyclists call 'bonking'? Is there any chance you've just run your glycogen stores down to nothing and your body/muscles are just-- outta gas? It feels *awful* when you do, your body just goes 'NOPPEEE!' and feels very much like what you describe.

Carbs are your friend, so fuel your workouts ("don't diet on the bike"). 90g of carbs an hour (mixture of fructose/maltodextrose) is the ballpark most recommend now for a decent effort.
posted by Static Vagabond at 2:20 PM on February 23, 2021 [6 favorites]

It's almost never a heart attack but you should know the signs. The signs are sometimes more subtle in women. But, I moved a bunch of heavy, wet, wood and then felt terrible, faint, pukey, cold sweat-y. If you call your doctor and say the word heart, they'll say ER. I had shitty health insurance and the rule-out-heart-attack visit was appallingly expensive, and it wasn't a heart attack. Staying hydrated is very good, even mild dehydration can be a problem with exercise. Agree that muscles can run out of food, so take a banana or other fast calories with you.
posted by theora55 at 2:59 PM on February 23, 2021 [1 favorite]

What you are describing sounds more like “pushing past your cardiovascular limit” than “MI.” I don’t think you can give yourself a heart attack merely by exercising hard—assuming you are in good heart health. (IANAD, TINMA) It could also be the aforementioned bonking, which is also not fun and is cured by eating lots of ice cream.
posted by computech_apolloniajames at 3:17 PM on February 23, 2021

Best answer: As someone who is in his 50's and in the Normal Times does quite a bit of hard physical labor under the hot sun, this sounds to me a lot like dehydration/low electrolytes/low glycogen.

You don't have to get your heart rate up high (or have your muscles hurt) to wear yourself out. Especially if you're not drinking much water and sweating out all the salts in your body.

In the future, just . . . be aware of this. Pace yourself, take periodic breaks, drink water, have a granola bar or mixed nuts or something you can snack on, maybe a sports drink or two, or some of the powdered stuff you can mix with water. You should be (yes, it's a terrible word) proactive about this - drink before you're noticeably feeling thirsty, grab a snack before you're noticeably hungry. Sunscreen and a hat/bandanna over your head if you're actually in the sun. Wet your head covering periodically.

Honestly, when it comes to work, like, accomplishing a specific task rather than working out (I'm in no position to tell you how to run your workouts), lose the "no pain, no gain" idea. Every time I've had somebody on the job site have similar symptoms due to dehydration/etc., it's the guy who's trying to bust things out as fast as possible or be all Tough Guy and do MOAR WORK and is just ignoring all of our suggestions of, "Hey, take 5 and grab some water, dude." "No, no, no, I'm great, I feel fine, let's hump this out!!" And then boom, they've got the shakes and have to lay down for half an hour and pant, and they're a lot less use to me than if they'd just taken that 5 minutes and the chug of H2O.
posted by soundguy99 at 4:32 PM on February 23, 2021 [4 favorites]

Response by poster: Thanks, I never had heard the term "bonking"! This will improve my googling immensely. And this would explain why I never bonk when biking home from the brewery ;)

That day I was moving boxes, I was trying to get everything done before sunset, and I do remember running out of H2O. I guess next time I won't be too proud to stop at the gas station for a Powerade and Andy Capp's Hot Fries.
posted by RobotVoodooPower at 5:50 PM on February 23, 2021 [2 favorites]

You are talking about identifying symptoms that could be suggestive of a potentially life-threatening condition. Consulting a public internet forum full of non-professionals for medical advice is a dangerous and inappropriate strategy. I beg you to please ask your doctor about this instead.
posted by aquamvidam at 9:30 PM on February 23, 2021 [1 favorite]

It takes a lot of effort to bonk. Your body has enough readily accessible glycogen to permit you to ride for about 2½ hours at moderate intensity; after that, you're relying strictly on energy stored in fat—even for very lean people, this is a huge reserve, but accessing it is Not Fun. That would be a pretty epic gym workout. Dehydration or electrolyte imbalance sounds more likely, although with either of those you should probably be getting muscle cramps too.
posted by adamrice at 9:25 AM on February 24, 2021

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