Cycling UK Forum

How do you avoid a bonk?

In cycling, there is never a truer word than the saying ‘if you’re hungry, it’s too late’. The best way to avoid a bonk is to eat little and often during your bike ride and crucially make sure you eat before you feel hungry. This means ingesting about 100-250 calories of some form of high carbs every 30 minutes, even in the first hour of your ride. Whatever you choose to eat, the main thing is not to forget to. You may think you’d never forget to eat, but you might be surprised at how easy it is to forget on our cycling holidays when you’re coursing past beautiful sights. Some people like to set an alarm on their watch to remind them, but just be aware that the more you ride, the more energy you will use up and therefore the more you will need to replace. We always encourage our riders on our cycling holidays to make the most of the cake at designated stops and also take a handful of sweets (which our support crew always carry with them!) to pop in your pocket or saddlebag in case you need them. It takes practice to get into the habit of eating whilst cycling, but the consequences of forgetting to aren’t worth risking.

For 10y I've not had the bonk once. I'm on a lowcarb high fat diet for that period, keeping 38lb off.

horizon wrote: ↑5 Jan 2024, 10:16pm

LittleGreyCat wrote: ↑5 Jan 2024, 7:54pm There are two different aspects to this:

(1) You start out using glucose as fuel, then switch dynamically to using ketones - this can be difficult to impossible for some people. You can have more initial energy but less stamina. The switch over point can be harsh.

(2) You start and remain in ketosis - that is you have been eating very low carbohydrate so that your body has to produce ketones for your basic daily energy requirements. This IMHO is a better way to operate. You have less initial energy but more stamina. You don't have the pain of transition between energy modes.

AIUI, the body uses glucose for heavy-duty, anaerobic exercise - you tear off at speed, keep up a fast pace and charge up the hills. Obviously, you then have to re-charge quite soon.

Alternatively, you set off at a moderate pace, use some glucose to get you going and then transition slowly to ketones. A sprint up the odd hill might involve a burst of glucose but then you are back in steady mode. So really this transition depends not so much on your existing diet/regime but on your approach to the riding itself - you pass seamlessly through the bonk.

I'm wondering though whether you would actually have to forego the carbs on the ride itself in order to allow the body to go into ketosis and this I presume is the harsh transition you refer to.

531colin wrote: ↑4 Jan 2024, 11:29pmBonk recovery can be very quick ….., I wonder if it’s too quick for absorption of even simple carbohydrates. Could recovery be redistribution of carbohydrates from glycogen stores to muscles?

Oral carbohydrate sensing

Studies on trained athletes holding a sports drink in the mouth for 5 – 10 seconds show performance benefits of 2 – 3 %

Believed to be unidentified carbohydrate sensors in the mouth (i.e. it doesn’t just work for sugars)

fMRI studies show an unidentified area of the brain lights up when carbohydrate is present in the mouth – that area is believed to communicate directly with muscles

Known as ‘carb rinsing’ amongst endurance athletes – when footballers, tennis players, etc, are seen spitting out liquid, it’s probably a sports drink.

Effect greatest when the body most carbohydrate depleted.

Reference
Oral carbohydrate sensing and exercise performance, 2010, Asker E Jeukendrup, Edward S Chambers

Carbohydrate in the mouth enhances activation of brain circuitry involved in motor performance and sensory perception
Clare E. Turner, Winston D. Byblow, Cathy M. Stinear, Nicholas Gant
Centre for Brain Research, University of Auckland
https://doi.org/10.1016/j.appet.2014.05.020

The presence of carbohydrate in the mouth appears to activate a novel energy signalling pathway capable of improving human performance.. This signalling phenomenon... has been shown to attenuate declines in motor function associated with fatigue.

Another reference
Carbohydrate in the mouth immediately facilitates motor output (Gant, Stinear, & Byblow, 2010)

cotswolds wrote: ↑10 Jan 2024, 12:04pm

531colin wrote: ↑4 Jan 2024, 11:29pmBonk recovery can be very quick ….., I wonder if it’s too quick for absorption of even simple carbohydrates. Could recovery be redistribution of carbohydrates from glycogen stores to muscles?

For personal medical reasons, I've had to find out more than I wanted to know about this and concluded this isn't well understood. (There may be more recent research I haven't seen.)
...

Gearoidmuar wrote: ↑5 Jan 2024, 9:56am ...
The bonk is caused by a rapid drop in blood glucose, not necessarily to hypoglycaemic levels.
...

531colin wrote: ↑4 Jan 2024, 11:29pm ...
Just one more thing I can’t remember; do the different muscle fibres have different preferences for metabolising sugars or fatty acid?

Jdsk wrote: ↑10 Jan 2024, 12:10pm

531colin wrote: ↑4 Jan 2024, 11:29pm ...
Just one more thing I can’t remember; do the different muscle fibres have different preferences for metabolising sugars or fatty acid?

Are you thinking of the different types of skeletal muscle fibre, or the difference between skeletal, cardiac and smooth muscle?

Thanks

Jonathan

he more you will need to replace. We always encourage our riders on our cycling holidays to make the most of the cake at designated stops and also take a handful of sweets (which our support crew always carry with them!) to pop in your pocket or saddlebag in case you need them. It takes practice to get into the habit of eating whilst cycling, but the consequences of forgetting to aren’t worth risking.