LandKurt

I've read of bonking while cycling; a near collapse from lack of energy due to low blood sugar. I've always wondered how much it differed from the fatigue I experience on long rides. How will I know I've pushed too far?

On Sunday I tried pushing the limits of bonking by riding in the morning without breakfast and no fuel during the ride. I wanted to see how far I'd get before I was forced to eat the food I'd brought with me. I did a ride of 44 miles with nothing but a couple nuun tablets in my water. I did not collapse, though I was fairly fatigued the last half of the ride. I was surprised to get that far without eating anything and it actually beats my previous best distance for the year by a couple miles. The first half of the ride I managed 15 MPH at an average heart rate of around 140 BPM, the latter part of the ride was more like 13 MPH at 150 BPM. There's a definite effect, but it's not that dramatic. I was expecting something more extreme.

Though my fatigue was unpleasant I'd only rate it as a 6 or 7 on a scale of 10 (where 9 is wishing you were dead and 10 is collapsing). I not as worried about bonking as I was before because it doesn't seem like it's going to sneak up on me suddenly. I'm not going to give up on eating on rides or anything as I want to put off the feeling of fatigue as long as possible. I'm still trying to figure out the right combination of water, electrolytes, and carbs during the ride to keep me going.

So, are there degrees or shades of bonking in which I experienced a light bonk, or is the only true bonk one where you are on the edge of collapse?

Biggziff

I think your physiology plays a significant role in what you feel. A 150 pound rider doesn't have the reserves that many of us larger individuals do, thus the wall is more concrete for them.

sstorkel

The one time I bonked, I'd eaten a minimal breakfast, then pedaled a 51lb touring bike through about 20-30 miles and about 1000-1500 feet of elevation gain. I found, rather suddenly, that I had absolutely no energy. Didn't feel like I was going to collapse, but I didn't really have the physical strength or the mental endurance necessary to turn the pedals over. Even though I started eating immediately, it took me hours to recover. Admittedly, I did continue riding since I'd reached a relatively flat section of the day's route. I was only able to manage half my normal speed and even that seemed like a monumental effort. Eventually, I had no choice but to stop completely and spend an hour or two off the bike doing nothing. Had to take longer than normal breaks throughout the rest of the day. Made it through the final 30 miles and 2000-feet of climbing for the day, but it was tough.

Based on what you've described, it doesn't sound to me like you were fatigued but not bonking...

Seattle Forrest

I think hitting the wall or bonking is the far edge of a spectrum of being tired or exhausted. Any long ride is going to use up some energy, but if you push yourself and don't put any fuel in your motor, it can be much worse.

A few years ago, some friends and I were going to do a 20 to 30 mile ride, and did a very hilly metric instead. I bonked pretty hard, feeling exhausted to the point of worthlessness and awful the next day. Another day, I had planned on a short ride, but started to feel better as I went along, and wound up doing about the same distance, but more hills. I got very tired, and stopped for a "nap" along the way. Going down a hill, I realized I was going faster than I would normally be comfortable with for the conditions, and thought it was odd that this wasn't bothering me at all. Seemed like my mind wasn't quite as alert as it should be, and I forced myself to take it slow until I got home.

On the other hand, a typical long ride these days leaves me feeling tired, but good; slightly distracted in a pleasant way. After one of these, I'll come home, eat some fresh fruit, and read a Carl Sagan book. I think these are very slight bonks. They're only slight because of the conditioning I've been doing, and because I've learned that nutrition is important.

mkadam68

Yeah, sounds like you didn't bonk.

Bonking does sneak up on you somewhat suddenly because the first thing to go is your self-perception: you're not entirely aware of what's going on with your body. Some symptoms: dizziness, fogginess in thought, shaking of muscles (my hands do that), lack of power & endurance, HR feels high but isn't actually, rapid, shallow breathing, etc...

And bonking is a bad thing. It wipes you for the rest of the day, and sometimes 1 or 2 after. You get home, feeling like you need to eat alot. But that's not required. Just a good, nutritious meal, and rest.

Why people bonk is somewhat an art. It, of course, always has to do with food/nutrition intake versus energy expended. But some days, you need more or different nutrition than others. Sometimes, I have bonked due to not eating enough. Others, because i did eat. Still others, because my intake was fine, but the nutritional quality the previous day or two was not adequate & my body didn't have what it needed.

mwchandler21

I rode a mountainous metric on Saturday and my normal 30 hilly miles on Sunday. I normally ride 50 miles of hilly terrain on Saturday so the metric wasn't much more miles but it was about 5 times the climbing that I normally do. I felt fine until Monday morning. I went for a short walk during my morning work break, by the time I got back to the office I was dizzy and weak. Did I bonk 3 days after? I've rode full centuries and even rode 900+ miles last month so I wouldn't think so, but it seems that it may be a likely thing. Today after resting and eating last night I feel fine again.

wxduff

One time after riding out to the biggest pass around, and then climbing it, and then riding back, I hit a pretty big hill on the way back. After all the mileage and the effort, it was too much. About half a way up I got very weak feeling. I unclipped and had to sit down. For like half an hour. A bottle of water and a clif bar later, I felt ok enough to walk the bike the rest of the hill, and then I took enough break, and then limped home very slowly. Then I took a nap, for like 2 hours. And then I still felt like crap for at least a day. That is what I have come to know as bonking. I have avoided it ever since.

Neil_B

There are degrees. The first thing to go is judgment. I can speak from experience. On my 2009 tour, I had a hard day riding into DC in the hot weather. I was tired, hungry, and dehydrated. I had to wait for my host that night to ride back on the Metro to his home and return with his truck to pick me up. I began to have paranoid thoughts that I was going to be left stranded on the streets of Alexandria, VA, overnight, that people were going to steal my bike, that the other members of the tour group (most of them Bike Forums posters) were mocking me.... I was still able to ride, but I was clearly not thinking rationally. When you met me two days later, rested and fed, I was fine. (And thank you again for the lift to Baltimore.)

Fastflyingasian

+1 on this. i bonked on day 3 of a 3 day solo tour. i hit the wall so hard that every pedal stroke was like pushing a broken down car on the side of the road. then dreaded every down hill because i knew a uphill was coming. even seeing a slight uphill had to stop for a break because there was simply not enough motivation to pedal the whole couple minutes for what seemed like a 10ft elevation. it might as well been 1000ft elevation gain in that quarter mile. the scariest part was next, i was getting too hot and dehydrated and was at least a half hour or more in between towns. so by the time i made it to the next store a half hour away. im not sure i would have been able to confirm that i was on planet earth if asked . short to say i learned a very important lesson on nutrition because i still had at least another 75 miles to go till home. it took an hour of dumping warm water then cool water on me to get back into riding shape. when i ride long distance i use a watch to remind me to eat and drink within a certain time to keep me from running a deficit. obviously i still did and bonked anyways.

LandKurt

You're welcome, Neil. I'm glad I had a chance to meet you when you were in the area. I see you've continued to have adventures since then. I basically ignored biking for a year and a half, but I've been getting back to it vigorously since the end of June. This was an attempt to understand my limits better.

Neil_B

I don't understand limits. Why would anyone want to stop me, including myself?

nkfrench 

My bonks generally include some tears and blubbering, sitting on the road with my legs twitching, and finishing the ride averaging 3mph the last few miles with sit-down cool-off stops every mile or so wondering if I will ever make it home. It's not a happy feeling on a 40 mile rural ride where you're being dropped and you have no clue where you are and your phone isn't working. While sitting there, the sun is getting even hotter and the hills sure aren't getting any flatter. Throw in some sunburn, dehydation, bug bites, crusty shorts, and tell yourself you're getting "experience".

mtnbud

I typically don't bonk unless I've been riding for 60+ miles with no additional calorie intake. I've learned you can't make up those calories when you bonk. If I'm going to be riding further than 40 miles, I make sure I take in some calories by mile 40. I don't worry about bringing extra calories if my ride is going to be 45 miles or less. Everyone is different, but that's where the cut off is for me.

A long day in a string of long days is definitely not the same as a long day after a day off. It's amazing how many calories I'll consume on a week long bike tour. Buffets are golden on tours.

Bonking will knock you down hard. One moment you'll be cruising full out happy as a clam and then next moment you'll be struggling on the flats in granny gear barely able to turn the pedals.