Energy use on and off the bike

[silentC]

Something which I have noticed but am yet to understand, and I was wondering if anyone can shed any light: I have a tendency to become a little hypoglycaemic if I go without eating for too long. For example I might go do a bit of gardening in the early morning before work. If I leave it too long before coming up to the house, sometimes I can feel quite bad and it takes a while after eating before I come good.

I had some blood tests but nothing diagnosed yet, although I haven't really pushed it with the GP because as long as I make sure to eat, all is good. Anyway I'm taking steps to look into what's going on there.

However here is the weird thing that I don't understand: I never eat before going for a ride, and I take very little food with me, just a museli bar or two, yet I have never had that feeling on the bike. I can go without real food for 6 hours on the bike, but I can't make it past 8am if I'm just working in the garden. Why don't I get the same symptoms when doing that sort of exercise?

[kb]

Do you watch your hydration more on the bike?

[lobstermash]

I'm a bit the same. I wonder if it's got to do with how much blood is pumping when you're on the bike, vs other activities. It's particularly bad when I'm doing an extra training load on top of normal kms. I get dizzy just stretching and taking a deep breath...

[cyclotaur]

I often get a little dizzy standing up from a resting situation (say on the couch) to walk to the kitchen or whatever....My theory is that when I'm laying about my heart rate drops right off towards its low-ish resting rate and then lags the sudden elevation by a few seconds.

Personally I don't think it's wise to do anything much straight after getting out of bed, specially if you're a deep sleeper - takes a while for everything to fire up.

[silentC]

Do you watch your hydration more on the bike?

I'm pretty bad with that too, they say as you get older the thirst reflex tapers off. Last week I did 100k and only drank 1 1/2 bidons. I ate one museli bar and drank a large cap at halfway. I was pretty hungry by the time I got home but I never felt weak.

I was reading about type II diabetes and they said that in the early stages you can trigger the insulin response through exercise, so I'm wondering if the type of exercise you do on the bike is triggering your body to get energy from somewhere it isn't able to at lower thresholds of activity.

I guess there is a hormone or something in the endocrine system that is produced under exercise but isn't present normally. It's weird because it can make you feel quite physically sick and irritable, if you let it go too long (low blood sugar that is), yet you can go for hours on the bike and feel fine.

[Mulger bill]

You need more water than that Silent, about a litre an hour during exercise was what I was taught many years back.

I often get a little dizzy standing up from a resting situation (say on the couch) to walk to the kitchen or whatever....My theory is that when I'm laying about my heart rate drops right off towards its low-ish resting rate and then lags the sudden elevation by a few seconds.

Postural hypotension, happens regularly to me if I get up too quick. I always sit on the edge of the bed for a little while after waking just in case.
Yes, it's a Wikilink so never treat it as gospel but it's always a good starting point...

[silentC]

You need more water than that Silent, about a litre an hour during exercise was what I was taught many years back.

Yeah I used to do a lot of bush walking and was constantly told I wasn't drinking enough. It helps with recovery too. I just never think of it when I'm on the bike

None of this answers my question though. How come I can't go for more than a couple of hours without food just working around the house or even sitting in my office chair, yet I can go flat out for 4 or 5 hours without any real food on the bike?

[Mulger bill]

When you're riding, you are usually concentrating on anything but your belly

[silentC]

Ah, so your theory is that it's mind over matter...

You could be right because as I rode the last 5k of my 108km/2100m ride this morning, I started to think about poached eggs on toast and did start to feel some pangs of hunger, possibly as a result.

[kb]

You could really confuse the issue and go for a long trainer ride inside

[silentC]

I made an hour once. That was enough!

[Mulger bill]

You could really confuse the issue and go for a long trainer ride inside

Rather sit on the couch and poke my legs with a fork thanks...

[kb]

I made an hour once. That was enough!

But did you make it past 8am?

[madmacca]

You need more water than that Silent, about a litre an hour during exercise was what I was taught many years back.

The problem with firm rules like this is that it ignores the conditions. Assuming you are well hydrated before you start, on an early morning ride, half a litre an hour may be more than enough. A midday ride in summer may have you drinking far more than this.