Metabolism, eating and fuelling for cycling

[Jon in Sweden]

I fitted a power meter to my gravel bike today and took it out for a spin. Only on tarmac though as all the gravel roads and smaller roads are covered in slush, which is lethally slippery (even with aggressive studded tyres).

I pushed hard (about 95% of what I could have done today I think), and averaged 332w for 1hr 8m. Normalised 355w. HR average 154bpm. Online calculators seem to suggest a calorie burn of about 1557kcal (23 kcal a minute!). This might well explain my enormous food consumption!

[Psamathe]

My daily calorie needs for cycle commuting vary between 1500kcal (if I take it very easy) to about 2200kcal (if I push really hard).

Is that a Garmin estimate or a Bike Calculator (or similar) estimate? I've found that different Garmins give different estimates with the same data and having/not having a heart rate monitor changes the estimates it gives me.

Ultimately, it's a matter of interpreting the various estimates in a way that the bottom line makes sense.

I'm a bit of a wimp when it comes to winter cycling (my fingers and thumbs were hurting at 4C today despite two layers of gloves) so the weekly mileage reduces and my waistline increases (I'll add 1 to 2kg by the time spring arrives as cold weather also makes me more hungry) and the challenge is to burn off that excess before the next winter arrives.

Even having a cadence sensor or not can alter the Garmin calorie estimates. And as you say, different Garmin models give different estimates for the same ride eg 1030 gives higher estimates that a 1040 - tested same ride same sensors at same time - everything identical and at the end fairly different estimated, tested several times.

Ian

[JohnR]

I pushed hard (about 95% of what I could have done today I think), and averaged 332w for 1hr 8m. Normalised 355w. HR average 154bpm. Online calculators seem to suggest a calorie burn of about 1557kcal (23 kcal a minute!). This might well explain my enormous food consumption!

That's good that you've got the numbers to add up. Just remember that if you stop all the exercise for any reason then you need to train you stomach to want less food or eat bunches of carrots. There are plenty of sportspeople who have got somewhat overweight after retirement.

[Jon in Sweden]

That's good that you've got the numbers to add up. Just remember that if you stop all the exercise for any reason then you need to train you stomach to want less food or eat bunches of carrots. There are plenty of sportspeople who have got somewhat overweight after retirement.

I have been lucky in the past that in times where I've not been training, my appetite hugely reduces.

Did 3670 calories on a 3hr ride today. That was a bit extreme though. Even for me!

[ed.lazda]

If you have a power meter on your bike, you can calculate the kcal burned more accurately than any online tool. It all depends on how much work is done.

Basically, 100W for one hour = 360 kcal.

Work done = average power x time, in my example 100 x 3600 = 360,000 J = 360 kJ
Conveniently, there are roughly 4 kJ in a kcal, and you need to burn roughly 4 kJ of fuel to do 1 kJ of work.
So work done in kJ is roughly equal to fuel burned in kcal.

[horizon]

Basically, 100W for one hour = 360 kcal.

Am I right in thinking that 100W equates to sustainable, moderate cycling (i.e. 250W would be maximum output on say on steep short hills)?

And do you have a food equivalent to 360 kcal, e.g. half a sandwich?

(You can see what I am getting at here.)

I found this page very interesting:

https://blog.afaa.com/using-watts-to-am ... ing-drills

[Jon in Sweden]

Am I right in thinking that 100W equates to sustainable, moderate cycling (i.e. 250W would be maximum output on say on steep short hills)?

And do you have a food equivalent to 360 kcal, e.g. half a sandwich?

(You can see what I am getting at here.)

I found this page very interesting:

https://blog.afaa.com/using-watts-to-am ... ing-drills

It depends on the individual. I'm tall and heavy (major air resistance and a lot to lug up hills) and from my limited experience with my power meter (only done 4 rides with it so far) this is how it works out for me:

150w - barely moving
200w - gentle touring/recovery pace
250w - steady, all day pace. Pushing it a bit.
300w - current maximum 3hr pace. Tough, 150bpm
350w - current FTP.
400w - standard hill climbing power output whilst touring
500w - standard full send pacr if climbing
610w - highest reading for a Strava hill climb segment

[horizon]

And do you have a food equivalent to 360 kcal, e.g. half a sandwich?

I'm answering my own question here: a modest sandwich is about 300 kcal so that would require/be consumed in an hour's leisurely cycling (assuming I have understood all this correctly).

[horizon]

It depends on the individual. I'm tall and heavy (major air resistance and a lot to lug up hills) and from my limited experience with my power meter (only done 4 rides with it so far) this is how it works out for me:

150w - barely moving
200w - gentle touring/recovery pace
250w - steady, all day pace. Pushing it a bit.
300w - current maximum 3hr pace. Tough, 150bpm
350w - current FTP.
400w - standard hill climbing power output whilst touring
500w - standard full send pacr if climbing
610w - highest reading for a Strava hill climb segment

A little bit more internet digging tells me that 100 - 150W is about right for moderate cycling, but not, as you point out, a heavy person cycling up a hill.

[ed.lazda]

Am I right in thinking that 100W equates to sustainable, moderate cycling

It all depends on the individual. From his figures, Jon is far more athletic than I am. My FTP is about 200W, and "sustainable moderate cycling" is around 140W for several hours, probably going down to 130W if I ride all day. This means about 500 kcal / hr.

[Jon in Sweden]

It all depends on the individual. From his figures, Jon is far more athletic than I am. My FTP is about 200W, and "sustainable moderate cycling" is around 140W for several hours, probably going down to 130W if I ride all day. This means about 500 kcal / hr.

Not necessarily! Maybe just a lot bigger.

It's a bit like comparing the fuel consumption and power between a VW Golf and a Chevy pickup. There are lots of people who put out way less power than me that go quite a lot faster!

For example, Connor Dunne (of GCN fame) has one of the highest FTPs ever recorded (470w at 88kg) but that didn't give him particularly notable success in the pelaton.

I'm 1cm shorter than him (203cm) but carry any extra 12kg (of mostly upper body mass). Consequently, I'm as aero as a portaloo and 40kg heavier than your typical pro.

You can only work with what you have though. I'm stupidly tall and have to make that. Eating enough remains a bit of a challenge though!

[ed.lazda]

I'm as aero as a portaloo

That conjures up an image that is difficult to get out of your head

You're right, in w/kg my FTP comes out at 2.6 which isn't so vastly different from yours at 3.5 and, as you say, I'm probably significantly more aerodynamic. You'd leave me behind going up a hill but I'd tend to catch you up freewheeling down the other side.

I'm a bit of a glutton and my eating difficulty is the opposite of yours!