Question Blacking out

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Aug 30, 2020
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I have a friend that was in the Army. During basic training, when recruits were pushed to their limits, fatigued and (often) dehydrated), they blacked out. This was a relatively common occurrence. The Air Force actually did a study on the subject:

Lamb LE, Green HC, Combs JJ, Cheeseman SA, Hammond J. Incidence of loss of consciousness in 1,980 Air Force personnel. Aerosp Med. 1960;31:973-988.PubMedGoogle Scholar

It could be vasovagal syncope (passing out/fainting). After the fact, it may not be possible to get a definitive diagnosis. Often, doctors will work to rule everything else out and then might conclude that, yep, you must have fainted.

The key thing is to be aware that if you push yourself too hard, fail to hydrate, fail to get a good night's sleep, etc - fail to take care of yourself and be aware of your body, you can pass out and break bones, etc.
 
Sep 17, 2020
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I just suffered a blacked out while riding, same thing, many tests and they can't find anything. I have a fractured clavicle and some road rash. Oddly enough my blood pressure and oxygen levels were fine. There is a possibility of my BP go up and then drop suddenly causing the black out.
Thank You for your reply. I'm still undergoing testing. I will post if I get any solid answers.
 
Sep 17, 2020
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I have a friend that was in the Army. During basic training, when recruits were pushed to their limits, fatigued and (often) dehydrated), they blacked out. This was a relatively common occurrence. The Air Force actually did a study on the subject:

Lamb LE, Green HC, Combs JJ, Cheeseman SA, Hammond J. Incidence of loss of consciousness in 1,980 Air Force personnel. Aerosp Med. 1960;31:973-988.PubMedGoogle Scholar

It could be vasovagal syncope (passing out/fainting). After the fact, it may not be possible to get a definitive diagnosis. Often, doctors will work to rule everything else out and then might conclude that, yep, you must have fainted.

The key thing is to be aware that if you push yourself too hard, fail to hydrate, fail to get a good night's sleep, etc - fail to take care of yourself and be aware of your body, you can pass out and break bones, etc.
Thanks for the input. In my case, everything was normal. I'm almost 50 years old. I was at the end of a comparably easy when of riding. I wasn't dehydrated or sleep deprived. Long term fatigue & age could be a factor. Without facts, thats just grasping at straws, though.
 
Aug 30, 2020
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Thanks for the input. In my case, everything was normal. I'm almost 50 years old. I was at the end of a comparably easy when of riding. I wasn't dehydrated or sleep deprived. Long term fatigue & age could be a factor. Without facts, thats just grasping at straws, though.
I'm 64. Plenty of straw-grasping with my doctors, too. I never considered bicycling to be hazardous, but now with 7 broken and displaced ribs and a separated shoulder, I'm not so sure. I did feel just a little bit odd, slightly dizzy, before I passed out. So now I really have to pay attention to any little signals like that, get off my bike ASAP and lie on my back with my feet up in the air!
 
Feb 24, 2021
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I am another casualty to this about 6 weeks ago. I thought I had hit a pothole when I came to, but don't remember the split second of panic before, so now thinking I have passed out. It was early morning and still dark on a country lane, with some traffic around including another nurse to the rescue. I was feeling fine and not pushed myself at that point, also had radar on bike so knew no vehicles close by. Had a few days in hospital and a couple of broken teeth, bike damage to a front wheel spoke, bars, stem and just really face damage all seemed like an over the bars incident. A colleague got me thinking it wasn't when he told me of someone they knew who blacked out on a their motorbike and ended up in a wheelchair in a vegetated state. The analysis they received was a domant neck/spine injury which had been slightly knocked into life to cause the passing out. I am now worried if I continue to cycle or like others here have no reoccurrence and don't want to give up something I love, but worried for my family if it does happen in a worse way next time or even happen in a car.

I had been told a week or two earlier that I had mildly high blood pressure and I also ended up with a small blood clot in one eye, which I had put down to the impact as that eye was virtually closed for the first day from the swelling. Also had a small brain hemorrhage, but was not deemed to be anything significant.

So many mysteries on this thread, not sure if jumping to conclusions to say many very related, with just the cause not being known.
 
Sep 17, 2020
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Wow! Sorry about that. It’s been since August that mine happened & still no answers. I’ve had echo cardiogram, ekg, eeg, mri & on & on. Might never have an answer. It’s frustrating. I need the bike now, more than ever.
 
Sep 17, 2020
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Just to continue this, in the hopes that maybe, someday, this thread finds answers for someone. In the end, I have no solid answers. After 7 months off the bike & every test imaginable, I'm riding again. As mentioned by others, it could have been blood pressure related. I was also riding at night, through the city, where I often would use my blinking headlight. Though epilepsy test proved negative, through EEG testing, its possible that I could have had a Blood Pressure issue &/or some type of seizure. These are all speculation, of course. I've had no previous or new occurrences. Been on the bike for 3 weeks & everything has been normal. Let's hope it stays that way....
 
Aug 30, 2020
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Just to continue this, in the hopes that maybe, someday, this thread finds answers for someone. In the end, I have no solid answers. After 7 months off the bike & every test imaginable, I'm riding again. As mentioned by others, it could have been blood pressure related. I was also riding at night, through the city, where I often would use my blinking headlight. Though epilepsy test proved negative, through EEG testing, its possible that I could have had a Blood Pressure issue &/or some type of seizure. These are all speculation, of course. I've had no previous or new occurrences. Been on the bike for 3 weeks & everything has been normal. Let's hope it stays that way....
I may have mentioned this before, so apologies in advance. When I blacked out and fell, I got a grade III shoulder separation and 7 fractured and displaced ribs. A friend in the military said people passed out all the time in basic training, from fatigue and dehydration. The Air Force did a study supporting this. I get migraines after pushing myself too hard, usually without realizing it. As soon as I stop pushing, I get the migraines. SO, long story long, I am not as aware of myself as I need to be. I must consciously assess my condition frequently, to see if I am pushing myself beyond the limits my body can withstand. By the way, multiple MRIs, MR angiograms, EGG, ECG, two week wearable heart monitor, cycling stress test, blood chemistry workups, some performed at the Mayo Clinic. No definative answers from any of those tests. Haven't been on a bike since. Have considered riding a tricycle with seat belts and 4-way airbags.
 
Sep 17, 2020
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I may have mentioned this before, so apologies in advance. When I blacked out and fell, I got a grade III shoulder separation and 7 fractured and displaced ribs. A friend in the military said people passed out all the time in basic training, from fatigue and dehydration. The Air Force did a study supporting this. I get migraines after pushing myself too hard, usually without realizing it. As soon as I stop pushing, I get the migraines. SO, long story long, I am not as aware of myself as I need to be. I must consciously assess my condition frequently, to see if I am pushing myself beyond the limits my body can withstand. By the way, multiple MRIs, MR angiograms, EGG, ECG, two week wearable heart monitor, cycling stress test, blood chemistry workups, some performed at the Mayo Clinic. No definative answers from any of those tests. Haven't been on a bike since. Have considered riding a tricycle with seat belts and 4-way airbags.
Interesting. I get migraines but, not usually from pushing myself. My doctor continually tells me to drink more water but, I feel I drink as much as I can. The week of my incident, it was my Friday, was my light week. I wasn’t pushing hard at all, all week. I have halved my intake of caffeine. Try to stay hydrated, have always eaten pretty well. I’m happy to be back on the bike but, certainly a bit Leary. Knowing something is wrong, isn't exactly the diagnosis one wants. It would be nice to know why something like this happens, so it can be avoided or treated
 
Aug 30, 2020
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Interesting. I get migraines but, not usually from pushing myself. My doctor continually tells me to drink more water but, I feel I drink as much as I can. The week of my incident, it was my Friday, was my light week. I wasn’t pushing hard at all, all week. I have halved my intake of caffeine. Try to stay hydrated, have always eaten pretty well. I’m happy to be back on the bike but, certainly a bit Leary. Knowing something is wrong, isn't exactly the diagnosis one wants. It would be nice to know why something like this happens, so it can be avoided or treated
"A half an ounce a day, for every pound you weigh" might work as a rough rule of thumb, but nearly clear urine is what you need. But passing out could be from so many things. Outside of always wearing a GoPro, pulse oximeter, wearable EKG, etc., you may never know for sure.
 
Any 'blackout situations' other than when riding? During other exercising, or strenuous work?
Also consider whether your clothing or head position might be interfering with blood flow in your neck.
 
Apr 23, 2021
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Hi, This is my first post because I found this while Googling "Black out while cycling".

I am an avid cyclist, 50 years old who mostly does 30-50 mile rides and I do a lot of singlespeed riding (pavement, mountain, and gravel). I ride about 3 times a week (70-100 miles each week). I weigh 160 lbs, and I am 5' 9".

On April 10 of this year, I was mountain biking a trail I have ridden over 100 times. It is relatively flat (500' ascending), 13.5 miles long and takes about 52 - 54 minutes to complete. I was not dehydrated, and I ate a little before my ride as I always have. Temps were about 60 degrees, partly sunny. Local area is SE Michigan.

I was 37 minutes into the ride, having just climbed a short section and was descending when I crashed.

I have no recollection of the crash. According to Strava, and my Garmin connect, I did not move for 28 minutes after the crash. Two individuals found me, but I do not remember anything until I started riding back to a road (after the 28 minutes) where an ambulance, that they called, checked me out.

I also refused treatment, rode back to the trail head, and drove home.

I had no dirt on my gloves meaning I never put my hands down. My helmet was lightly smashed in the (right) front and I tore all the ligaments in my right shoulder. I had huge bruises on my left hip, and under my left knee (pedal?). I think I went over the bars because both of the brake levers (it was a mountain bike with drop bars) had dirt on the tops of the hoods. The seat was broken (carbon rails).

I have not gone to any other doctors yet, but am in the process of setting up more appointments.

Best of luck to everyone else.
 
Jun 21, 2021
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Having the same issue. My issue happens EVERY ride. I get really confused and dizzy, with periodic blacked out vision. It can happen once or multiple times during my ride. I ride between 30 and 100 miles. I have several minutes to stop and lay down and after 5 minutes I feel 100% again. I get migraine headaches outside of riding, but while riding on bumpy roads I get stabbing pains in my head and my vision blacks out and once closed in on me on a really rough road. I decided to ride on my trainer and see what my blood pressure was doing during these periods and I was having significant drops in blood pressure with very narrow readings (difference between to and bottom number 87/71). I am a triathlete training for Ironman so I found it interesting that I began to have neck pain while swimming. I had a neck injury 10 years ago and the doctor suspects the blood flow is being compromised to my brain due to structures in my neck. I am getting an MRI so I would be happy to share if that is the case. My gut tells me this is the problem. FYI-cardiologist diagnosed me with Postural Orthostatic Tachycardic Syndrome, I feel this doesn't give me any answers though because the cause is unknown.
 
Jan 9, 2010
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Here's my blackout experience from 2 weeks ago, and some background:
  • Had been diagnosed with costochrodritis, an inflammation of the cartilage around the sternum towards the end of last year. Was preventing me from pushing hard during race training and in time trials. Symptoms were a tightness/pressure on the front of the rib cage. Treated by specific stretching exercises. Possible cause - a weakness/strain where the cartilage join the sternum created by heavy lifting. Usually manifests first thing in the morning, so triggered by a sleeping position (probably on my side)
  • so a stop-start traing/racing over the winter/during the spring. Decided to take a break from racing to reduce the inflammation and just do long distance riding for fitness/stamina maintenance
Saturday 5th June - cycled 200 hilly miles in 16 hours. No chest issues.
Monday - 15 minutes into a short recovery ride on my new TT bike, I stopped to adjust the saddle, stood up, felt light headed, and fainted. Woke to find a crowd around me, one of whom said she'd lost my pulse for a minute or more and had applied CPR. I could remember phone numbers etc, but was partly paralysed, although all feelings returned within 5 minutes. Medics checked blood pressure and everything else - all normal.
Went to A & E, where tests were inconclusive - again, everything normal, apart from a slightly elevated blood enzyme that could have been caused by the CPR or a heart attack. Was kept in overnight, then was sent to a cardiac unit for an angiogram, just to cross off the possibility that it had been a heart attack. To the surgeon's surprise, this discovered one of my main coronary arteries was 99% blocked, so they performed an immediate angiogram to fit a stent.
So the cause of my blackout has been identified as a heart attack (caused by a hereditary high cholesterol level).
I still have the costochrondritis to solve, but that could have been masking angina.
But reading the above cases, I do wonder if a neck constriction played a part. Last year I abandoned a 12 hour TT due to excruciating neck pain, which I never get riding a normal road bike. Anybody need a new TT bike?
 
Jul 4, 2021
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Aaah I seem to be latest in a long line. Depressing to know that there are no definitive answers. Blacked out on 26 June on a route and speed I have done countless times. No memory of my fall, came too with helmet broken, nasty gashes on my knuckles, left knee and left elbow. CT and MRI came back negative. Yet to see a cardio but not hoping for much as I just had my annual in April and everything was normal. No damage on the bike as with everyone else. Resigned to ride the trainer for the foreseeable future. I did have my heart rate recorded on strava. Anyways I could analyse the gpx file? Searching for an app but no luck so far.
 
Jan 9, 2010
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I've received a bit more information on my blackout.
The belief is that a coronary artery was almost completely blocked when I set off on my short ride, but then a small lump of the cholesterol deposit called plaque dislodged and blocked the artery completely, causing the blackout. When I collapsed it unblocked and I regained consciousness. This is known as a Type 1 MI:
Then the angioplasty operation to fit the stent permanently reopened the almost completely blocked artery through the fitting of the stent.
The underlying cause is my hereditary high cholesterol level, which the statin and aspirin I now have to take for the rest of my life will reduce. I'll have a blood test in a couple of months to see my how much the current statin dosage has reduced it by, and then my GP will adjust the dosage if it is not enough.
But I'm told that it was a one-off occurrence and should not reoccur due to the stent and the medication.
For me it is interesting that it was only the angiogram that uncovered this - the blood tests, ECG and echocardiogram did not.
So this week I will go out on my bike at last, 4 weeks after the heart attack, having done a week on the turbo with no issues other than a bit of post-operation discomfort as the stent settles down.
 

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