GrasB
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jimboalee said:
Option c mainly... but surely I'll want to take more energy in per mile if I'm operating at 20 to 25mph than 15 to 20mph?
How much should I eat?
- Thread starter jimboalee
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Option c mainly... but surely I'll want to take more energy in per mile if I'm operating at 20 to 25mph than 15 to 20mph?
I'll give you a head start.
Yes, the power and therefore the kCals requirement for motion is greater if you ride the mile faster.
But, the windchill you experience negates the difference.
It is worst of all in a cool sidewind. Most rides are of generally circular route ( start and finish at the same place ) so this is the average of what you'll get all day.
Riding at 10 mph takes 6 minutes to cover the mile whereas riding at 20 mph takes 3 minutes. The total Cals required for Tractive motion is roughly 3 times at 20 mph as it is at 10 mph.
Windchill and heat wasted keeping damp clothes warm however, can be an equal or greater drain on the body as the Tractive effort – a 5 mph sidewind can be 2 kCals/min.
So at 10 mph, you're out in the breeze for 6 minutes and at 20 mph, 3 minutes.
So all in all, at 10 mph;
( 1.5 kCals/min x 6 ) + ( 2.0 kCals/min x 6 ) = 21
At 20 mph;
( 4.5 kCals/min x 3 ) + ( 2.0 kCals/min x 3 ) = 19.5
This is just one example where riding faster is more efficient than riding slower.
Do some more sums and you'll find an optimum speed for efficiency dependent on the meteorological conditions on the day.
This is one reason I don't dawdle along AUK 100s in the cool.
Yes, the power and therefore the kCals requirement for motion is greater if you ride the mile faster.
But, the windchill you experience negates the difference.
It is worst of all in a cool sidewind. Most rides are of generally circular route ( start and finish at the same place ) so this is the average of what you'll get all day.
Riding at 10 mph takes 6 minutes to cover the mile whereas riding at 20 mph takes 3 minutes. The total Cals required for Tractive motion is roughly 3 times at 20 mph as it is at 10 mph.
Windchill and heat wasted keeping damp clothes warm however, can be an equal or greater drain on the body as the Tractive effort – a 5 mph sidewind can be 2 kCals/min.
So at 10 mph, you're out in the breeze for 6 minutes and at 20 mph, 3 minutes.
So all in all, at 10 mph;
( 1.5 kCals/min x 6 ) + ( 2.0 kCals/min x 6 ) = 21
At 20 mph;
( 4.5 kCals/min x 3 ) + ( 2.0 kCals/min x 3 ) = 19.5
This is just one example where riding faster is more efficient than riding slower.
Do some more sums and you'll find an optimum speed for efficiency dependent on the meteorological conditions on the day.
This is one reason I don't dawdle along AUK 100s in the cool.
Riding a 100km Audax on a heavy old bike.
Earlier in the summer, with chances of rain, I decided to ride a DIY 100 on my Halfords Apollo County 3 speed Sturmey gent's sit-up-and-beg.
It was a more exhausting day than usual. I would have ridden my Dawes Giro 500.
The Apollo is 35lb with a Cd of 1.18 compared with the Dawes 24lb and 0.96 Cd.
Trying to ride at a similar power outlay, I averaged just over 16 kmh for the 100 km, where I would have averaged 20 on the Dawes.
I've just got round to finalising a Power/Cals sheet for the Apollo, and I was surprised to see ( but it sure felt like it from memory ) the Calorific demand for the Apollo was DOUBLE for the same weather conditions.
Which only goes to prove that "If anyone tells you how many calories to eat, don't believe them." Best to work it out for yourself.
I really was expecting more shouting….
Earlier in the summer, with chances of rain, I decided to ride a DIY 100 on my Halfords Apollo County 3 speed Sturmey gent's sit-up-and-beg.
It was a more exhausting day than usual. I would have ridden my Dawes Giro 500.
The Apollo is 35lb with a Cd of 1.18 compared with the Dawes 24lb and 0.96 Cd.
Trying to ride at a similar power outlay, I averaged just over 16 kmh for the 100 km, where I would have averaged 20 on the Dawes.
I've just got round to finalising a Power/Cals sheet for the Apollo, and I was surprised to see ( but it sure felt like it from memory ) the Calorific demand for the Apollo was DOUBLE for the same weather conditions.
Which only goes to prove that "If anyone tells you how many calories to eat, don't believe them." Best to work it out for yourself.
I really was expecting more shouting….
coruskate said:
In addition.
A sensible pro racer will fill up based on the assumption he MIGHT have to ride the whole race at racepace on his own.
If he gets pulled along by the peleton, that's a bonus and he can go light at the feeding stations packing his back pockets with food for a JIC moment later in the race.
In a situation ( which is not impossible ) where just after the start, there is a crash and he is the only rider who survives the tumble, he will ride away furiously knowing he has a chance of keeping the lead and winning the race.
If he'd adjusted his food intake assuming he'd be drafting a group all day, he'd be shagged, and stuffed for winning the race.
