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The 'bonk' advice

James14100James14100 Posts: 23
edited March 2011 in Commuting general
Hi all,

I did my first commute to work last week on my mountain bike. All went well and I was really happy when I got to work, no fatigue and a great pace.
See here: ... y/26190414

However I had a really busy day which didn't help and as I usually ride after work anyway I just took my usual lunch (two sandwiches, an apple a pear and two bananas)
on my way home I totally bonked out. The fatigue after 13miles really kicked in and I found it a struggle to pedal in big ring.
See here: ... y/26220484

I can only presume that it was due to lack of food, or the food I'm eating. I was really keen to make this a regualr thing but I don't want to try again until I know I'm not going to suffer in this way.

Can you help?




  • Stop at a garage and get a flapjack, dude.
  • kelsenkelsen Posts: 2,003
    Could be many things:

    lack of food - try eating something 1-2 hours before your commute home
    headwind - a strong headwind can double the effort on your part
    fitness - your body isn't used to the commute yet, though judging by your log, you seem pretty fit already
    speed - how fast were you going? It's gonna be tough if you're trying to maintain a 25mph average!
    bike - a full susser with knobbly tyres isn't going to make your commute easy. Have you changed to slicks and locking out the suspension if able to?
    technique - you say you struggled in the big ring. Are you pedalling efficiently? Mashing a huge gear is always harder than spinning in a smaller gear
    physiology - sometimes you're just tired for various reasons

    Don't let that first ride put you off. 13 miles each way isn't a huge distance (assuming you're on fairly flat tarmac) for a commute. Persevere and you'll soon get used to it.
  • Kelsen - It's 17.5 miles, the 'bonk' starts after 13.

    Having had this happen to me a few times, I'd say it's lack of food. Your fitness seems more than enough for the distance, and the sudden onset says it's definitely the bonk.

    More energy supplements would help. I like the High5 range.

    The amount of food you eat seems quite low. It might be worth upping your intake.
    My commute:
  • Hi,

    Thanks for the replies


    bike - I'm riding a crosscountry hard tail on knobblies but "high rollers" I wont be switching to slicks as I ride more offroad than I will be on the commute.
    speed - I wasn't pushing on the way to work just going at steady pace 15mph
    technique - I'm often cycling in Big ring with the third smallest at the rear. This is the gear I'm most comfortable with on road cycles although I know it's all on the feel.


    Thanks for the food advice. I think the solution must be food. I'll try eating more on my next attempt, possibly next week if the weather is good. I'll make up some healthy flapjacks and increase my ammount of food and see how it goes.

    I know physically I'm capable of doing this. I just need to sort my head out to know that I'm not going to suffer so it can become a regular thing.

    I'll let you know how I get on next week

    Anymore advice in the meantime is welcomed


  • James
    Its suprising how much difference eating a bit more will do, porridge always works well for me.
    Stick with the commuting though, I was the same at the start but then you get used to distance. Still can be tough after hard day though!!
  • Cheers mate.

    Well considering I have a half day tomorrow and the weather is looking good I've spied an opportunity for another attempt. Heading from home this time, Stamford. A further 9 miles but I've planned ahead with the food so should be ok.

    Will let you know. Thanks again for the advice

  • All went well. Although ended up going on a 15 mile walk after work instead of cycling back. Food seems to be the trick! :-)
  • Pleased you've sorted it out. :-)
    My commute:
  • rightyrighty Posts: 278
    I'm sorry but I think you are confusing a lack of energy and mild fatigure for bonking out, it isn't.Bonking out is when have used most of your energy reserves and barely have the strength to pootle along, it is unlikely to occur after such a short distance/time but the factors kelson mentions above do of corse come into play. you will know if you ever bonk out as you will feel a strong desire to lie down, find yourself asking strangers for food and have problems turning the cranks in any gear let alone the big ring :D Office Fitout Reconfiguration and Relocation 24/7
  • Lycra ManLycra Man Posts: 141
    I have read this account with interest. I commute 15 miles each way, on a hilly route, so I know some of the difficulties. I thought your lunch was quite a lot of food, as I have one sandwich, one apple and one banana, but then I have a desk job, and don't know how active and demanding your work is. Whatever you do in a day, you need fuel.

    So if you think you are not eating enough, have more to eat, but maybe space it out, so you are fuelling for your ride home.

    To begin with, take youir pace steady, and build from a base that you can manage. If you find it too hard, get off and walk. Just find a level you can manage, and build up from there.

    Keep at it, and good luck.

    Lycra Man
    FCN7 - 1 for SPDs = FCN6
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