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Near-blackout while running?

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I just attempted to go running. I was going a very slow pace, just warming up, about 5 minutes into it. Had to stop for a stoplight. Felt a little nauseous and next thing I know, the whole world is going black. I reached for a nearby telephone pole just in time. It came and went pretty quickly - I didn't exactly faint. But that was very weird.

I came home and I feel very weak and shaky. I'd just eaten a 500 calorie meal before this run (carb-loaded too: 1-cup nonfat yogurt, 1 cup frozen raspberries, 1 banana, and a 150-cal energy bar), so I don't think the problem was too few calories. But just in case ,I'm now eating a can of tuna.

Only thing I can think of is low blood pressure maybe? I do run on the low side.

Anyone else have this?
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I have chronically low blood pressure and take meds when it gets really low. Have you seen a cardiologist?  My cardiologist put me on a diet that requires me to add salt to everything, eat 5 small meals a day and drink at least 8 glasses of water. I am also to cut out all sugar from my diet (except for fruits). This diet has given me pretty good results. I used to walk around in somewhat of a daze some days because my blood pressure would be so low that I wasn't getting enough blood to my brain to keep me coherent. Also, I was advised to continue to exercise but be careful not to push it. Listen to your body. You'll know when it's telling you to stop.

Yes, I saw a cardiologist awhile back, because I had chest pains while running, but they ruled out any heart problems - the going theory is chostochondritis - but I haven't had any further issues like that since. The cardiologist ran a stress test, EKG, ECG, the whole nine yards and gave me his blessing to run.

The doctor has only said that if I was taller, he might put me on meds to raise my BP, but since I'm so short, it's not an issue he's concerned about. It probably true that since I've lost weight and quit smoking and taken up running, my BP is probably lower than ever these days.

The salt thing is interesting. Hmmm. Except I think I ate a lot of salt yesterday and this weekend! In fact, I'm sure I did, since my weight is up 2 lbs this morning from retention.

I did listen and I did stop. I'm going to wait until my girlfriend gets off work, and ask her to run with me, just in case I keel over!
P.s. this is disappointing because I had planned to run an "anniversary" 5K this weekend... one full year since I started running again. :-(
Jenmcc: don't be disappointed. Your health is important. Sorry to hear about that. Hope you will feel better soon.

You can always run 5K another time:)
Perhaps you're anemic? I am (though not nearly as bad as I used to be) and occasionally when I haven't had enough iron I get dizzy really easily and black out alot. Maybe you should see a doctor or something..
I have done nothing but seen doctors lately... like a friggin' revolving door. :-(

Most recent bloodwork all checked out normal, including iron. No anemia. But maybe I'll use this as an excuse to have a big juicy burger tonight for dinner!

Hi there-

 have you ever worn a holter monitor? (a device that monitors your activity for 24-48 hours..)

otherwise, This happened to me once when I started training and my electrolytes were out of balance...Good luck!

maybe you were just dehydrated?!  I ran the Army 10-miler recently and towards the last 2miles I started to get dizzy, light-headed, the hairs on my arm were raised (but it was 95degrees outside), and I was tingling all over....  ALL because I was dehydrated.  Several people during the race blacked out or had to stop off to the side b/c they hadn't gotten enough water prior to and during the run.

 Not that I'm in any way belittling the possibility of something related to your heart, but if you have been under the care and supervision of doctors and are eating right, etc. then it may not be something so complicated and just a case of dehydration that caused your momentary black out.

 Something to think about anyway...

BEST OF LUCK to you if you decide to run and good luck figuring it out.

not enough sodium will dehydrate you and drop your blood pressure.  take a day to rest up, make sure you are drinking plenty of water and Gatorade to balance the electrolytes, getting some sodium, eat some bananas (potassium), and then see how you are feeling.  My initial guess is that your electrolytes are off...nothing to worry too much about...just need to get back on track.  hope you feel better!
I don't think it was dehydration. This was in the middle of the day, I'd had plenty of water already (but not too much - just right, I think), and I'd only gone 5 minutes. It was following a weekend of eating out a lot, so I don't think low sodium was an issue either (my weight was up 2 lbs - usually happens when I overdo the sodium). Electrolytes -  don't know. I did have a banana within one hour of the run. I eat a banana every day.

I suspect it might be my nicotine gum!! It is true I chewed more than normal this weekend, because I have a friend visiting who's a smoker and I don't want to start again. I'm cutting back to see if that helps, if not, I'll call the doctor again. I didn't black out today on my run, but I did feel dizzy and lightheaded again when I slowed down near the end.
i agree with the anemia question because i too get frequent blackouts due to it... especially in the mornings b4 i have breakfast
I know you said you don't think it's dehydration, but your symptoms sound like what I was dealing with a few months ago.  Whenever I would stop jogging after 6+ miles (which I know is much more than 5 minutes, but the point is that it only happened when I stopped), I got that dizzy feeling, like I was about to black out.  (which was very scary when alone in a totally empty gym)  I also got nauseus and felt really really horrible.  I also have blood pressure on the low side.  People told me that it sounded like I was dehydrated, but I didn't believe it because I drink (and drank) what I thought was plenty of water and I was jogging indoors, in air conditioning, not in the summer heat.  I've learned that I can't just STOP running.  I need to jog in place at stoplights and do a cool down every time.  I also need to drink more water than I thought I did.  I read an article about how your body can be working really hard to pump blood to your legs so when you stop jogging suddenly, it's still pumping a lot of blood there - resulting in a lack of blood to your head, especially if you're dehydrated to start out with - less blood volume in the first place.  Add to that low blood pressure, and it's even worse.  I don't know if that's what happened to you - best bet to see a doctor to rule out anything serious, especially if it happens again.  But try drinking even more water next time and don't stop running suddenly if you can help it.
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If your urine is clear or the color of lemonade you are not dehydrated - that is the best indicator - drink more or cut back depending on the color -

as far as the black out feeling, since your heart and bloodwork is fine; and it sounds like you eat well - I believe joyfulake figured it out.  Its the sudden stop in running.  Even at the end of races you'll notice they always make you walk it off - they don't allow you to just stop at the finish line - if you do, many people would have that same feeling.  I get it myself and remind myself to keep moving even at red lights. 

The nicotine gum does have side effects; but due to the fact that the feeling only happened at that point, its probably irrelevant to your gum. 

Good luck and I hope you'll feel better!
Joyful, that makes sense - the sudden stopping thing combined with low blood pressure. Still not sure about the dehydration part - my urine is nearly always clear as can be, except first thing in the morning. I drink tons of water. But the blood in your legs/stopping suddenly makes a lot of sense!
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jen -- a doctor once explained to me (after I fainted) that it could be due to your heart rate/blood pressure being high and plummeting back to low (which is normal for you and me, but still a long way to plummet).

Also sounds a bit like a head rush, when you stand up too fast. Do you get those?

Give yourself another half hour after you eat to get some of that food digested.  Also, get yourself a heart rate monitor.  For training they are the greatest thing since sliced bread anyway.  Keep your heart rate under (and this is a very general rule) (220 - your age) * .60 at first, and work up to maybe *.8 later on.  It could be thatyou just got in over your depth.



I mostly run and sometimes bike, and this sort of thing can happen to me.  If I am pumping it up a hill after I've been going all out for a good half hour and I have to dismount in the middle of pushing myself I get nausea and feel faint (not to the point of blacking out).  I would try running in place to keep the blood flowing, or run down the side of the street you are crossing until there is a break in traffic.  Any way you look at it though, this isn't a good sign.  Your cardiovascular system is telling you something when it can't adapt to changes in your brain's demand for blood flow, and I would certainly make this known to the doctors you see so often.  Your body is designed to keep blood flow/pressure to the brain constant to the detriment of your other organs, and if this blacking out happens on a regular basis, then something needs to change.  Whether it is a lack of electrolytes, O2, pressure, or H2O it isn't the norm.
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