Utilising Indoor Measured Power for Outdoor Riding

[Splash]

OK Guys.

Here's the scenario.....

• Bike 1 - Neo Smart Indoor Trainer with a 10 speed drivetrain rear cassette. All training on Bike 1 using acquired indoor measured power metrics (including FTP calibrated zones, etc.).
  
  
• Bike 2 - 11 speed drivetrain rear cassette with P2M power installed. Race and ride long endurance group rides on bike 2.

I will not be using Bike 2 on the NEO at all due to the different speed cassettes and not wanting to compromise my carbon frame in any way. Is it possible to utilise the Bike 1 calibrated power metrics for Bike 2 rides - knowing that different riding conditions, FTP and power meters exist? If so, how? If not, what is my best option to utilise bike 2 power meter, given that I have spent all training time indoors on a different setup?

How do others work around this in similar situation??


Splash

[shovelhd]

I used to test on the bike I raced on. In your case, that means two tests, or a test on the race bike with an offset for the trainer. The drivetrain doesn't matter that much. The factors that will affect accuracy across platforms are a) two different power meters and b) road versus trainer.

I've always used a 7% offset for the trainer, but you have a Neo Smart which is direct drive. I don't know how that would affect you. The main reasons trainer effort is harder for the same power is a) no let-up, the power delivery is constant and b) poor air quality and compromised cooling. The Neo doesn't change this.

[Joachim]

^^ 7-8% is a good offset. The few studies that have been done showed a 5-10% in ftp between outdoor and indoor testing and that % is different for each individual. Do a test for each bike and then calculate your zones. Your carbon bike won't be affected by using an indoor trainer. I have lots of riders with carbon bikes on lemond trainers, on wahoo Kickr and on compu trainers. Anyway that's not your question, but to tie in with ShovelHD, even direct drive riders show about a 6-7% discrepancy between outdoor and indoor watts.

[11.4]

I've usually found with athletes that there's a lot more than a 7-8% differential. You don't recycle the metabolized oxygen around you on a trainer, so you have to blow it away effectively or the quality of your air supply goes down. You also develop a bubble of humidity and heat around you on a trainer -- same kind of issues. Plus you don't change your bike's position like when you tilt it, ride uphill or down, and so on. Psychologically they are very different beasts, which alone is worth 10-15% (probably more like 25% in my particular head). There's simple heating effect on a trainer. And on and on.

I'd suggest you run tests on the trainer and measure FTP, power at corresponding heart rates, and so on. Both short and long efforts. That way you can see how your body responds differently on the two systems. Even then, the psychological element is not an insignificant element that you may not be able to calculate fully. I don't expect one power level to be convertible directly to power on the other system on a consistent basis. Rather, track both your power, whether on the road or on the trainer, and your heart rate and recovery -- just like you'd be doing on the road. If your heart rate and recovery are wonky, even if your power is constant, it tells you something important. Don't just look for a formula comparison.

[Joachim]

Originally Posted by 11.4

I've usually found with athletes that there's a lot more than a 7-8% differential. You don't recycle the metabolized oxygen around you on a trainer, so you have to blow it away effectively or the quality of your air supply goes down. You also develop a bubble of humidity and heat around you on a trainer -- same kind of issues. Plus you don't change your bike's position like when you tilt it, ride uphill or down, and so on. Psychologically they are very different beasts, which alone is worth 10-15% (probably more like 25% in my particular head). There's simple heating effect on a trainer. And on and on.

I'd suggest you run tests on the trainer and measure FTP, power at corresponding heart rates, and so on. Both short and long efforts. That way you can see how your body responds differently on the two systems. Even then, the psychological element is not an insignificant element that you may not be able to calculate fully. I don't expect one power level to be convertible directly to power on the other system on a consistent basis. Rather, track both your power, whether on the road or on the trainer, and your heart rate and recovery -- just like you'd be doing on the road. If your heart rate and recovery are wonky, even if your power is constant, it tells you something important. Don't just look for a formula comparison.

I've started correlate lactate values with power output and heart rate during indoor be outdoor efforts. I trust my data collection and will share the results down the road if you are interested.

[93legendti]

Do these factors still apply if you use a fan for cooling while on the trainer?

[HenryA]

And how does listening to music with earbuds effect power output? Faster with or without?

[Ti Designs]

Wait a second, is this 5-10% difference a linear function? Does it hold across the entire range, or are we talking an estimated difference at FTP? Most of the power meter based training methods I've read seem a bit off, but this need for global accuracy in a world where fudge factors are needed makes no sense at all. Compare apples to apples. Compare indoor training numbers to indoor training numbers, outdoor training numbers to outdoor training numbers, and use the same power meter.

[Joachim]

Originally Posted by Ti Designs

Wait a second, is this 5-10% difference a linear function? Does it hold across the entire range, or are we talking an estimated difference at FTP? Most of the power meter based training methods I've read seem a bit off, but this need for global accuracy in a world where fudge factors are needed makes no sense at all. Compare apples to apples. Compare indoor training numbers to indoor training numbers, outdoor training numbers to outdoor training numbers, and use the same power meter.

Well he is not using the same power meter since he already decided that he doesn't want to 'compromise his carbon frame' and that's why the recommendation is two different power ranges. One for each bike. Two tests, one for each bike. One for indoor and one for outdoor.

[11.4]

Originally Posted by Ti Designs

Wait a second, is this 5-10% difference a linear function? Does it hold across the entire range, or are we talking an estimated difference at FTP? Most of the power meter based training methods I've read seem a bit off, but this need for global accuracy in a world where fudge factors are needed makes no sense at all. Compare apples to apples. Compare indoor training numbers to indoor training numbers, outdoor training numbers to outdoor training numbers, and use the same power meter.

Linearity is a major question mark as well, but Ti always gets to the heart of the matter: the same basic question I was asking ... why bother? You come to realize that they simply aren't comparable, either in terms of the body load imposed on the rider or the relationship between power output and level of effort. I was mentioning heart rate and recovery as a simple parameter that may actually be a better comparison between road and trainer simply because power output gets filtered through a lot of variables on the trainer and isn't necessarily comparable. Joachim suggested lactate readings, which are an excellent approach but possibly a little beyond the average rider on a trainer in his living room. What we've been experimenting with are inexpensive finger-tip oximeters. They are pretty good proxies for lactate testing in a noninvasive way and easy to sample in real time. You can buy simple small oximeters quite cheaply, and they can give very useful data for indoor training. They measure your nearly instantaneous work effort rather than cumulative effort (as in lactate testing), so you can compare to power, heart rate, and perceived effort. It's not too bad.

But what's important is to understand that one should test against oneself under comparable conditions. I frequently get emails from riders who want to have an equation for predicting track performance from trainer performance. I always have to repeat the same precaution that they simply aren't comparable. Even if you could establish a translation between the data, you wouldn't really find much use for it. They are simply different.

[Joachim]

Originally Posted by 11.4

Joachim suggested lactate readings, which are an excellent approach but possibly a little beyond the average rider on a trainer in his living room. What we've been experimenting with are inexpensive finger-tip oximeters. They are pretty good proxies for lactate testing in a noninvasive way and easy to sample in real time. You can buy simple small oximeters quite cheaply, and they can give very useful data for indoor training. They measure your nearly instantaneous work effort rather than cumulative effort (as in lactate testing), so you can compare to power, heart rate, and perceived effort. It's not too bad .

I agree that for the average rider, lactate testing in his living room might go a bit too far, but if a rider already owns two setups with different power measuring devices.... You get my drift. Anyway, I hope Splash finds what he needs to get the most out of his training.

[Splash]

Great responses guys.

Really interesting information to delve into for more options.

I like the idea of using lactate and oxi-meters as a common base point.

Yes Joachim, I would be interested to see your correlation of lactate values with power output and heart rate during indoor be outdoor efforts.

Can I ask what tool you are using to obtain the lactate values?


Splash

[shovelhd]

Just test on the road bike. Simple.

[Splash]

Originally Posted by shovelhd

Just test on the road bike. Simple.

Are you meaning to test Bike 2 on the NEO and note any differences in wattage outputs between the P2M crank PM and the inbuilt NEO PM and then adjust your outdoor riding wattage (FTP, zones, etc.) to meet both indoor and outdoor PM's?

Splash

[shovelhd]

No. Test outdoors on the road bike with the P2M. Offset 7% for the other bike on the trainer. It doesn't have to be any more complicated than that.