How to fuel to avoid cyclist's 'bonk'

"Bonk" is caused by the depletion of glycogen stores in the liver and muscles and is unlikely to occur in an hour, but I understand what you guys are gong through. You need to continue to press on at low glycogen stores before the body shuts down and say no more. The liver can store roughly 100–120 grams of glycogen and in the skeletal muscle there's roughly 400 grams of glycogen. That's roughly 2,000 calories. Your body will not permit complete depletion before bonking. Assuming bonking occurs some where around 90%, that 1800 calories. Also assuming a metabolic efficiency of 22%, that 396 calories to the pedals or 1,657 Kj an hour or outputting ~460w steady for one hour. Only the best world tour competitors can do that. As indicated, you need to keep going after that without fueling to get the bonk. How long? That depends on the intensity maintained assuming no fat is burnt during the entire period. The more condition, the higher the fat burn thus prolong the glycogen use.

Fueling on the bike is personal preference thing. I would start with liquid, Gatorade or coke mid-ride. I don't like gels. They are messy and I need lot of water to wash it down. On longer rides, I might stop mid ride or towards the end for a coke or a Gatorade mixed with my water. I prefer solids food. Nature Valley Fruit & Nut is my go to. I like Cliff and UCAN bars also. On rides under 3 hours I normally don't eat. On longer rides, >4 hours, I start eating around the 1.5 hour mark and generally consume a bar every 90-120 minutes, so not much calories for refueling. You need to train you stomach for it. On those day, I generally have a carb rich breakfast before starting. I never really have success fueling the night before.

I took a 17 years hiatus and jump back on in 2014 after throwing my back out and couldn't shake the discomfort for over 6 months. I was also >35# overweight, taking statins into my second years, and got label as a pre-diabetic. 5'8" also. You just need more saddle time to get back into shape. It took me two years before I felt comfortable riding in a group (not skill but speed to keep up). I'm still slow up the climbs (especially after the last year and gaining 15 # back) but can hold on the flats. In 2019, I finished my first double century and was shooting for the California Triple Crown before being side tracked. I hope to get that in 2022. If you haven't got a bike fit, you might want to consider that. I was lucky that I was able to jump back onto my old collegiate racer without much problems after two years riding mostly indoors on a trainer (build up an old frame set I had kept since college and set it up with a more upright position). After picking a new bike in 2017, I got a fit done.

I seem to remember Fort Story has some empty roads with some rollers when I was station there in '95 and often wish I had my bike then. Good luck and keep riding.

That really isn't bonking.
It may well be the cumulative caloric deficit though or simply an excessive deficit though.

I'll describe what happened when I bonked and you will see how extreme it is.....
Had planned and fuelled for a 60 mile ride but felt good and randomly decided to push it up to 80 miles which was pushing the absolute limit for me at the time.
About 75 mile mark tiredness very suddenly became feeling like I was riding up a constant hill, with two flat tyres and a howling headwind (it was flat, tyres were fine and no wind). Crushing fatigue and poor co-ordination.
Once I checked the tyres I knew on some level what had happened but was too mentally confused to stop for a carby drink or snack despite going past numerous shops. In fact too confused to unclip my feet when I stopped at a junction with inevitable consequences. Taking on carbs at home brought me "back in the room" within minutes although I felt pretty awful for hours.

What you describe doesn't fit the bonking scenario (complete glycogen depletion) as you say you had zero energy from the off.

There isn't a best macro proportion (that's not a great way to look at fuelling exercise anyway).
The idea of carb loading the night before also is a bit old-fashioned approach - keeping a reasonable amount of carbs all the time and keeping your deficit low is more effective than day before loading.

A carby breakfast (cereal for example) and maybe stopping for coffee and cake should be more than enough for a leisure ride, if it isn't I'd look more at your overall dieting strategy rather than a narrow view of on the day fuelling.
Is your and your husband's rate of weight loss in a sensible range for people wanting to exercise?

You aren't going to have a big calorie burn from a flat 20 mile leisure ride and quite possibly a majority of your energy will be coming from fat and not carbs anyway. I've got to be riding briskly before carbs overtake fat as the predominant fuel.

The other thing is build up your CV fitness steadily, 10% distance increase per week should work but it could be that 20 miles is too much right now.

OP, I agree with the responses above, in particular because you describe your husband as feeling "off" right from the start. That suggests to me that he started the ride in a depleted state, perhaps from the prior day's calorie deficit or just starting the ride in a fasted state. In general, riding requires some fuel. Reading the comments above should give your husband an idea of where a change might help.

Finally, I echo the thought that if your riding increases in duration, intra-workout fueling becomes a consideration. I'm riding quite a bit these days, so fueling the long rides is not only necessary for the day of the ride, but also to help recovery for the next day's work.

Jthanmyfitnesspal wrote: »

Yes, @sijomial describes a real "bonk." Those can be very bad. Like when a marathoner or triathlete starts staggering around on the course. It's dangerous, for sure, particularly on a bike! I've gotten very close, to the point where I got lost and confused and didn't know how to get home. I always ride with a packet of Gu in my pocket in case I run into a problem. But, anything with sugar will work!

I've only bonked once or twice, but the first time it happened I remember crying because I wanted to go home but I didn't know how (I was in my home city, in a familiar location). Fortunately I was with a running buddy who understood what was going on.

Bella_Figura wrote: »

Thanks for the input folks.

Before this morning's ride he had a crap night's sleep and woke up feeling unrefreshed and lethargic. I proposed deferring the ride, but he was adamant he wanted to go. He had peanut butter on toast for breakfast, and we set off about an hour later.

I told him that everyone has bad days and this was just one of those. He feels fine now...no lasting damage done! But he wants to know if there are any nutritional tips that would prevent a repeat occurrence.

Yep, I'd say it was simply a continuation of his fatigue from poor sleep and maybe too few calories. Next ride will be better!

paperpudding wrote: »

Clearly bonk doesnt have same meaning as it does here

@paperpudding

It does.
At least it makes a nasty experience sound like fun.

But it's origin in cycling probably goes back to the other meaning of bonk as in hit or knock - similar to runners calling hypoglycaemia hitting the wall.

"Should have ducked, got bonked on the head."