A curious question

barrybridges

Short but sweet:

Throughout the past few years I've mixed cycling with running - and I've competed in both sports (albeit at a very low level). I've run the London Marathon and I've completed the Marmotte, but on both occasions I haven't set the world alight!

In running, I can comfortably complete a half marathon in 1:45 without taking on any energy gels or food, but in cycling, after 1:45, I'll be starting to bonk.

I don't really understand why. I had assumed that running is a more energy intensive sport (higher ave HR, more energy used as more limbs in motion etc) but when I'm riding - even at a steady L3 ride, I really whack out unless I eat plenty.

I'm not concerned as the cure is simple (eat) but I'd like to understand, if I can, why I might be bonking after 1:45 on a bike when I don't when I run the same amount of time, even though running is more resource-intensive.

Any thoughts?

keef66

I can't answer your question, but I'm the other way round. I can cycle all day, but ask me to run to the post box 400m down the hill and I'm fit to vomit. What's that all about?

DaSy

Do you wear an HR monitor on the run to be able to compare exertion levels?

ut_och_cykla

My guess would be that you are close to your limit when running but as running is so aerobic/steady you dont quite reach empty - whereas on a bike you maybe ride less steadily, charge up hills , keep up with others etc and manage to empty your tanks slightly quicker - just an idea.
keef66 perhaps you're just not used to running!!

barrybridges

I can't work it out at all.

For example, when I set out on a club run, I find the pace really easy. Slow, in fact - slower than if I were to ride on my own (but that's nice, sometimes, to have a casual training ride rather than thrashing it). But still, even on a club run, I'll start to bonk after about 1:30 - 2hrs if I fail to eat properly, even though I've found that time 'easy riding'.

Whereas I find running hard but still don't bonk.

It's almost as if riding at 60% MHR is a quicker route to bonking that 80% MHR.

dennisn

barrybridges wrote:

Short but sweet:

Throughout the past few years I've mixed cycling with running - and I've competed in both sports (albeit at a very low level). I've run the London Marathon and I've completed the Marmotte, but on both occasions I haven't set the world alight!

In running, I can comfortably complete a half marathon in 1:45 without taking on any energy gels or food, but in cycling, after 1:45, I'll be starting to bonk.

I don't really understand why. I had assumed that running is a more energy intensive sport (higher ave HR, more energy used as more limbs in motion etc) but when I'm riding - even at a steady L3 ride, I really whack out unless I eat plenty.

I'm not concerned as the cure is simple (eat) but I'd like to understand, if I can, why I might be bonking after 1:45 on a bike when I don't when I run the same amount of time, even though running is more resource-intensive.

Any thoughts?

Interesting question. I haven't run in years, but like you say I could do a half marathon
(in closer to 2 hours)and not need any more than water. Never looked at it like that. As I said, interesting.

Slimbods

barrybridges wrote:

I'm not concerned as the cure is simple (eat) but I'd like to understand, if I can, why I might be bonking after 1:45 on a bike when I don't when I run the same amount of time, even though running is more resource-intensive.
Any thoughts?

I'd have thought two things. First you might be favouring running over cycling in training, so your a more efficient runner than cyclist? Otherwise, it might be that cycling is more intense on just the lower body than running, so your hammering the legs only and exhausting them quicker?

Just guessing, not an expert

Brommers76

barrybridges you mention you can run 1:45 half marathon but is this a race? I only ask because if I were racing a half marathon I would fuel for the two days before. If I go for a club ride I just eat normally. Is it a like for like comparison? Are you topped up before both examples?

oldwelshman

Its unusual to bonk at 1:45 to be honest, especially at club run pace. For a race of that distance at high intensity I think most racers would just probably use one bottle.
Fatigue can seem like the bonk. You do not say how far you ride per ride or how many miles a week.
Recently after the bad weather and 3 weeks off having done lots of miles in the weeks before, I only did a 35 mile ride and felt like I had done the marmotte !! Also felt like I had bonked but knew I hadn't.
Within 4 rides I felt much better.
It may be you need more miles under you belt so to speak.
Edited crap spelling

Jaguar.

I'm with old welshman here, though I'd not be putting any mikes under my belt!

I started cycling a few years back and experienced the same thing, I used to eat because I thought I was bonking, or about to bonk. With the benefit if hindsight, my legs were fatigued, I can now ride for the same sort of times as I could run without fuel befoe needing anything on the bike.

So what happened on the Marmotte then? If you bonked at 1:45 you'd be top of the first hill? I'd be surprisd if you could recover sufficiently from a proper bonk on the descent to manage the next 6+ hours of riding?

Anonymous

I have started using no food at all on rides. I only ride for fitness, no club runs, racing etc and am always on my own so might be different for you.

I ride for about 4 hours 4 times a week, covering about 60-70 miles per ride. I think I get the "bonk" about 90 minutes into my rides but after riding for another 15-30 minutes I am fine again for the rest of my ride, only using electrolyte drinks (High 5 Zero).

I used to cram energy drinks and gels in at least every half an hour but as I am trying to lose weight I found it to be defeating the purpose of half my miles. I then read an article about Training Low Racing High and switched. And am now losing about 4 pounds a week again (2 before). Here is a brief passage explaining things

"This is a protocol where you train low without carbohydrate (using ZERO for example) and compete high with a carbohydrate drink like Energy Source.
The theory is that by forcing your body to train without carbohydrate you adapt and burn more fat overall as fuel. In addition you are able to tolerate low glycogen levels better in race conditions. This is currently practiced by a number of pro cycling teams. We have one research study running and are scheduling others to look at this in depth." (Taken from PBK Blog)

Might not work for everyone, in the heat of summer, or to already "healthy weight" people but for me it is working great.

Tom Butcher

I'm another with OW - I reckon it's psychological. You feel like eating on the bike because it's easy to carry food and eat it on the bike whereas running doesn't really suit stuffing bananas and flapjack in your mouth on the go - it's a bit like taking a packed lunch to work it'll always be eaten well before lunch - don't take a packed lunch and you wont feel hungry til 12.30-1.

johndoran

If you have ever had the bonk you would know it and you wouldnt recover after just a drink of electrolite in 15 mins. Believe me the bonk leaves you almost unable to turn the pedals, you have cold sweats ,feel faint and the only thing that works is food and loads of it.