Bonk?

team47b

The 'bonk' or hypoglycemia will occur if you have too much insulin or too little 'glucose in your system. Glucose is produced by eating carbohydrates. Your brain has a preference for glucose, but can use muscle glycogen.

If your blood glucose falls below 70mg/dl you will bonk. It takes 15grams of carbs under 15 minutes to restore your glucose levels.

If you start your exercise below 100mg/dl you can drive your blood glucose down below 70 in less than 8k distance.

Normally your liver will release a flood of glycogen into your system before you feel the effect of low glucose, your liver and muscles hold enough glycogen for about 90 minutes (assuming it is full) of exercise (average) so you can bonk at that point. This time limit is determined by effort, hills, headwinds, fitness levels etc. You will need to eat a 'normal' meal or more to restore this store, it's total capacity is about 2000 calories.

'Bonking' in sport is usually a term reserved only for the effect after fully depleting glycogen stores, not for hypoglycemia.

pinarellokid

good post full of usefull info. helps to know the background science behind it

marcusww

the playing mantis wrote:

so in answer to the ops question, we need more info.

The night before I ate a lot at Pizza Express including the kids left over pasta but was a good boy and only had 1 pint!

The ride was supposed to be 45 miles but due to our group of 11 not having the correct route and leader we ended up at 55 plus my ride home of 4 miles. It was that 4 miles that did it - I think also the 'mental knowing' that I had finished didn't help but I had drank 2 x 750ml ribena on the way round.

Rather than the recovery drinks you can get I find that the kids Nesquick straberry milkshake powder in milk helps!. I had 2 pints of that and a massive beans on toast afterwards! I still felt a bit down an hour later so I had a gel to see if it would help and I think it did.

But the lesson I learned was to not skimp on taking enough food! And was probably lacking fitness from a 3 week hol full of food and ale!

apreading

Marcusww wrote:

only had 1 pint!

There's the problem... lightweight!

Mikey23

Anyways, no real harm done and a lesson learned

Tjgoodhew

I had a "bonking" experience for the first time on Sunday. 30 miles in and over 2k ft of climbing (quite difficult to achieve in Essex) i felt good and decided to stay out and ride the opposite way from home. After 45 miles i turned into a head wind and that was it i was finished!!!

Had 10 miles riding into a head wind and it was the hardest 10 i have ever rode. Speed dropped from close to 20mph down to 12mph and i had to will myself to keep going and not call in. At the end i have a 0.2 mile 8% climb and that was hell.

I got in, sent the mrs to the shop for two cans of coke downed them and before i knew it i was fine.

I have no idea what caused it. I wasnt riding on a hangover, had eaten well the day before, had breakfast, energy drinks and gels on the ride.

The only thing i can put it down to was the climbing - i was sprinting up some pretty steep but short climbs early in my ride in search of some Strava PB's and i think it just wore me out.

So next ride instead of taking a couple of gels its going to be a bag of Jelly babies so if it happens again i have got enough food to get me home

Thats if they last that long !!!!

the playing mantis

2k of climbing in essex? pray tell the route.

pinarellokid

lol.. i take it Essex is kinda flat

Pituophis

I've only ever had it happen once, in my mtb days on a ride of less than 30 miles. Lots of climbing, very warm day, not really enough to eat and ran out of water around 7 or 8 miles from base. Very poor planning!
All the hard work was done, leaving literally miles of fast down hill single track back to town, yet all I could do was barely sit on the bike while it slowly trundled downwards. I felt as if I didn't have the strength to hold onto the bars and I was shaking like a leaf, and was constantly afraid of falling off, even at very low speed. Felt like every minor stone would jolt the bars away from me.
While I obviously wouldn't have lay down and died/been eaten by wolves etc, I don't think I could honestly have got back to the car without my mate's constant encouragement.
Got to the bike shop (we were parked behind it) where they made me a sweet brew and I ate 2 energy bars and within 20 minutes I felt pretty much back to normal. Wouldn't have liked to ride anywhere though!

It's never happened to me on the road bike yet, probably due to better food management, but you never know :shock:

Tjgoodhew

the playing mantis wrote:

2k of climbing in essex? pray tell the route.

The only way i could do it was riding up and down the hills in the Benfleet area - Vicarage Hill, Essex Way, Bread & Cheese and Church Road.

You can do it in a figure of 8 type loop and it works out about a 20 mile ride with about 1200ft find another 800ft from somewhere and your there.

If you did that and then went out to hanningfield you might even be able to get closer to 3k !!!!

djm501

Well - this has been the most informative thread on this subject I've seen on BR so far. I have certainly been educated and I am happy to bow to the knowledge of sports nutrition expert
I guess we do need to look outside our own areas of cycling to see the full picture.

the playing mantis

Tjgoodhew wrote:

the playing mantis wrote:

2k of climbing in essex? pray tell the route.

The only way i could do it was riding up and down the hills in the Benfleet area - Vicarage Hill, Essex Way, Bread & Cheese and Church Road.

You can do it in a figure of 8 type loop and it works out about a 20 mile ride with about 1200ft find another 800ft from somewhere and your there.

If you did that and then went out to hanningfield you might even be able to get closer to 3k !!!!

strava link?
may try it one day, but tend not to venture down sarf, thought you were going to say you went up and down north hill a few times!

the playing mantis

whoops for you were talking m not ft. my bad

Tjgoodhew

2000m in Essex !!! That would be an acheivment !!

For what its worth here is the strava link - http://www.strava.com/activities/75612562