Estimating work required for a course?

If you are faced with doing an event and cannot ride the course, do any of you have a method for estimating how much work you will need to do to finish?

Gran fondos tend to me equivalent to a Tour or Giro mountain stage, so you could go by pro data, correct (it will just take me much longer to do that work).

For ultra events, I wonder how you figure the endurance required using kjoules for a 200 mile ride with 16,000 feet of climbing, for example.

Any thoughts/theories?

 

I ended up doing the Granfondo Marco Pantani earlier this year, at three days notice, to fill in for a clubmate. I completed the medium course as my training had been fairly light (CTL about mid thirties) and largely devoid of longer runs. The medium course was 152km and involved 3400m of climbing including the Gavia and Mortirolo (ouch!).

The Powertap summary of the ride is shown below

Entire workout (150 watts):
Duration: 7:12:41 (8:28:55)
Work: 3837 kJ
TSS: 379.5 (intensity factor 0.731)
Norm Power: 178
VI: 1.19
Distance: 92.044 mi
Hope this sheds some light for you on the demands of cyclosportive type events!

 

Depends on how fast you ride it, what you weigh(on the climbs at least), wind conditions etc. But knowing your FTP and what percentage you'll ride for that duration lets you make a good estimate. IOW if you think you'll average 200 watts for the event and finish in 12 hours then plan on something like 8600-9600 Calories for the day. 20-60% of those will come from fat stores and the rest from stored glycogen and carbs you consume during your ride. Typical topped up glycogen stores are in the range of 1100-1700 Calories for average adults depending on body size, muscle mass and gender. You really don't want to totally deplete those stores either since it's hard to catch up during the event if you get hypoglycemic(translation you bonk from low blood sugar).

As you can see there are a lot of estimates buried in this approach, you can't know with any accuracy your exact average power or what percentage of fat vs. glycogen that represents or what your personal metabolic efficiency is at the levels you'll be riding.... So those estimates listed higher in this thread(oops that's another thread) are probably equally useful and all have some error vs what you'll really burn.

Anyway, you can use those kind of estimates to come up with a feeding plan but personally I find I can only take in around 300-350 Calories per hour in solid and liquid form before I start having GI issues like cramping and bloating. So even if the numbers tell me I need more I can't eat more during the ride without running into other issues. I did a 206 mile race with over 7500 feet of climbing about a month ago and did some estimates before race day. That helped me plan my feeding but I ended up eating less than my estimates even though I rode faster than expected. I just couldn't make myself eat more than about 300 Calories per hour while riding hard. I finished the day strong and never bonked and certainly wasn't trashed afterwards so the feeding worked all right even on fewer Calories than expected. I averaged over 21 mph for the day and nearly 200 watts AP so I wasn't exactly slacking either.

Anyway, I'd suggest doing some feed planning estimates before some of your long training days and see how it works for you before your big ride. No sense in filling your pockets with food you won't eat. I ended up passing on full musette bags in the late day feeds and just going on liquids and what I was carrying but still ended up with a lot of pocket food at the end.

Good luck,
Dave

 

I rode that this year as well, though I am well out of shape (too heavy). My official time was 8:05, though I am sure you waited for about 25 minutes as I did on the Gavia once the traffic jam started!

My challenge is translating that effort to a double century, but I would guess the events I have done would require about 8000 kjoules of work ...

 

I think the intensity factor of ~0.7 is good estimate for one day events. On non-stop multiday events I've experienced the IF to drop to ~0.6.