Flu-like symptoms after intense workout today

What the heck happened to me today?

So this morning I did a 1 hour 30 minute Threshold interval workout (Beacon -4). I’ve been doing a program on TrainerRoad and am about 4 weeks in. This was the first threshold workout, and it had me at about 90-95% of my FTP (253) for 8 minute intervals. It was prob the hardest workout I’ve done to date and I had to lower the intensity to finish it, and even they I barely finished the last interval. I basically felt like I bonked on the trainer.

Now, before the ride I had a bagel w cream cheese, and afterwards I an apple before the wife and I headed up to her parents house for a bday party.

On the 2 hour ride there, I start to feel weird. Massive headache, chills, sweating profusely. After making 2 bathroom stops we finally arrive and I can barely walk while exiting the car, my entire body feels limp and weak. I go to the guest bedrooom to lay down and am just sweating like crazy, am extremely dizzy, have a headache, and am wondering if I need to go the fucking hospital at this point as this has never happened to me before.

My wife brings me a Gatorade and I slug that down, and that helps. It helps enough that I slug another one. After about an hour of recovering in the bedroom, the sweat finally stops and I feel well enough to go back out with the family. However, I still don’t feel great. I have heartburn and just overall don’t feel like myself.

My question is - wtf happened here? Has something like this ever happened to anyone else? Was I just extremely dehydrated? I don’t think I finished my water bottle on the bike, and we went out drinking two nights ago for the first time in forever. Maybe that caused this? Just too much of an effort for today?

It was very scary and embarrassing and I never want this to happen again.

Do you have a fever? What was your heart rate?

Probably best to at least call a tele doc to see what they say. Though more often than not they tell you to go in and get checked.

No fever, and my heart rate was normal throughout. My HR has been improving a lot over the last few weeks with all the Z2 and Sweet Spot work I’ve been doing. I was actually happy with the numbers too today despite the training load.

An hour and a half hard, close-to-threshold workout and all you fueled with before and during was a bagel with cream cheese? And then an apple afterwards?

How much water and sodium did you take in during?

Sounds like it could be really inadequate fueling and hydration (before/during/after) coupled with a really hard workout. I personally would have eaten 2-3 hours before the workout, and then started with 25g of sugar every 15 minutes starting 15 minutes before intensity started to ramp up for a hard workout like that. And, 1000 mg of Sodium per Liter of water for me.


Thanks. I really thought the bagel would be enough as I frequently eat one do those before my longer outdoor morning rides…I had a big water bottle with a Nuun tablet in it. But I didn’t finish it (which is honestly unusual for me).

Two, not-mutually-exclusive possibilities:

  1. hypoglycemia and/or

  2. “leaky gut syndrome”, i.e., infection from within as a result of a prolonged reduction in blood flow to the GI tract, compromising the integrity of the endothelial lining.

In any case, condolences…I have wrecked entire weekends after turning myself inside-out in the pursuit of athletic glory and/or scientific knowledge.*

*I of course was the primary guinea pig for the pilot experiments leading to this study that was part of my dissertation:


A bagel is ~50 grams of carbs, and slower absorbing, especially when you add on the cream cheese. I would have taken in 150 - 180 grams of carbs in that same time range for that type of workout. (Bagel is fine if it’s lower intensity)

One Nuun tablet is like 300 mg of sodium. I need 4X that per liter based on the sweat testing I did and personal experience.

You probably should have had enough energy on board (assuming you fueled well the day before and were topped off), but sure sounds a little bit like a Bonk to me and fueling / hydration could use some work.

Appreciate the info. I def did not fuel well the day before. I was hungover all day actually. I wonder if that aided in my dehydration…

I would guess you have your answer. Hung over all day the day before, didn’t fuel or hydrate well, hard threshold workout. I probably would have yakked all over my bike if I even tried the workout. :rofl:

Try that workout again, but go in rested, not hung over, topped off on carbs the day before, fuel more during the workout (gels or carb mix), try a higher sodium content in your mix, get enough fluids, I’d wager you feel a lot better.

1 Like

A hangover is caused by dehydration…that’s essentially the definition.

Your symptoms don’t sound very flu’ish, but maybe I am misreading them.
In any case, “exercise flu”, which is, flu-like symptoms after hard exercise without an actual infection is a thing:

So I started having chest pains the day after this and went to the ER. Turns out I was having a heart attack, at 33 years old, due to a completely blocked heart artery. Spent 2 days in the hospital and have been home recovering since Thanksgiving. Doing better every day but will be a while before I’m back on the bike.


Holy crap, wishing you a speedy recovery. Good lesson to all of us - probably best to err on the side of heading to the hospital when something like this happens.

1 Like

Holy crap. Glad you are ok… You never had any symptoms before??

1 Like

Glad you’re doing better. It’s definitely terrifying. I’ve felt wrecked after workouts but nothing like you described and typically functional if I eat something and rest. So definitely a lesson I’ll keep in mind if I have severe symptoms after a hard workout

Dang man… glad you went in to get it checked! Wishing you a speedy recovery!!!

1 Like

Holy Moly, thank goodness you had went to ER the next day!
Your symptoms sounded worrying , but I 'm not qualified to give advice, so didn’t want to speculate.
All the best for your recovery, and I’m sure you will be back on your bike once you are better.

Wow, talk about a misread by all of us internet experts (me included).

Glad you made it to the ER, and wishing you a speedy and complete recovery!