clones2

Got a Quarq Elsa to play with this year - paired with my Garmin 500. Supermagneto Pro Trainer indoors. Here's my issue today:

Ride 1 - on trainer (calibrated with garmin) - rode around and stepped up from 18-25 mph on my supermagneto pro to see what the wattage was for each mph on the trainer versus what Cycleops says it should match too on their power chart for the trainer. (They say at 25mph - equates to about 305 watts - about 210 watts at 20 mph) This the road setting... At 25 mph - I was only putting out supposedly 250 watts... much lower than what I thought it would be - and much lower than the cycleops chart which was supposedly verified with a power tap.

Ride 2 - so I head outside, recalibrate a couple of times, and go for another ride to ride for about half an hour just under threshold. Just a hard ride on about a 7 out of 10... I have a few intervals on flat sections for 3 to 10 minutes where Im doing 19 - 22 mph... 45 degree temps... and my avg output for each is from 260 to 300 watts. I was assuming before getting the power meter that my FTP would be about 275 watts...so these efforts seem to line up.

Ride 3 - back indoors to see if the numbers changed at all after being calibrated several times... Rode 10 minutes at 26mph on the Cycleops Supermagneto Pro - all out effort - legs burning, sweat dripping, very flat chart of power output. Wattage only 267....

So... what's going on here??? Why would the indoor and outdoor efforts be soooo far off from each other? Would it be the temps? Which should be more accurate.

I am a racer and can ride sub 1 hour 40km's fwiw. I was hoping these numbers would align more to help with training indoors and outdoors. Thanks for any insight.

CharlyAlfaRomeo

Test your FTP, do your training based on that number and forget about MPH on the trainer because you're not moving.

canam73

What he said.

Plus, trainer power charts are only estimates. They don't know your tire size, psi or how hard you cranked the roller on.

Also, most people have some drop off in power vs hr or perceived effort when riding in doors. Good ventilation and fans help, though.

clones2

I understand that... However - my outdoor FTP would be about 275 watts. My indoor FTP would be about 225 watts. That doesn't make sense on the same power meter... How can you go from riding 6 months outdoors with an FTP of 275... then move indoors for 6 months and start training off a new FTP that is 50 watts lower...? Seems pretty weird to me.

Matt2.8NJ

Clones2, get used to indoor power being low. That's just the way a lot of people experience it.

My power numbers look sad indoors, a hero outside.

Dunbar

Use your outdoor power numbers. It's not uncommon to put out ~10% less power on an indoor trainer. Some trainers are much better than others at mimicking outdoor road feel. This is one of many reasons that I refuse to ride indoors on a trainer

gregf83 

It's normal for indoor power output to be less than output particularly if you haven't spent much time indoors. Temperature is the primary difference. You don't have a 20mph+ wind cooling you down indoors. To mitigate the effects get the biggest, most powerful fan you can find or use a couple of fans. In addition the inertial load is different on a trainer than outdoors so that will feel different and perhaps take some time to get used to.

Do some searches on any cycling forum and you'll find you're certainly not the first person to notice this effect. If you ride a lot indoors your indoor power will likely get much closer to your outdoor number.

caloso

250 inside feels like 300 on the road to me.

CharlyAlfaRomeo

Is the power number coming from the same meter indoors as outdoors?

chaadster

I think the whole point here, the whole point with training with power, is that power is the yardstick, not speed. If you're benchmarking off speed, which as mentioned above is highly variable, what's the point of using power? The power measurement is a constant, independent of tire pressure, wind, slope, etc.

So the problem is not your meter, it's that you don't want to accept the numbers. And anyway, the numbers do not look divergent to me (assuming equivalent effort, which there is no way to determine with info given). Probably you should add an HR monitor to the mix to help determine effort level and fitness.

Toolish

Based on 20 min testing my outside FTP is about 245, inside about 210, HR and RPE for the tests was very similar. Have a big fan, so assume part of it is inertia of the trainer.

Main issue I have with it is how it affects PMC

clones2

Ok -seems to be fairly common. Im definitely not testing off of speed. I was just under the assumption that perceived level of exertion outdoors and indoors would yield similar results. Thanks for the insight here.

spdntrxi

this

simonaway427

FTP of 275 and sub 1hr 40km?

That doesn't add up unless your TT route is downhill.

topflightpro

After nearly six years of training with power, I can tell you that you should expect your power on the trainer to be about 10-15 percent below when riding outside.

Gregf83 did a good job explaining the reasons for this, and he correctly pointed out that if you searched, you would find lots of threads discussing this already.

Also, it's virtually impossible to tie power to speed. For example, on Sunday, at times I was putting out 250-260 watts and going 4 mph while at others I was putting out 0 watts and going 45 mph.

merlinextraligh

In my experience, my FTP indoors on the trainer is a bit lower than outdoors, but the variance is likely more in the 5% range.

That said, the preceived effort on the trainer to hit the right level for a particular interval is often substantially greater than is outdoors.

In other words I can hit close to the same watt levels, but it hurts more and takes more willpower. Thus tempo intervals indoors often feel as hard as steady state intervals outdoors.

canam73

Just to add to this, when doing tempo and recovery paced stuff outdoors the little bumps we do when going up small hills, off stops and into wind gusts really add up. My AP and NP for that type of ride is always way higher outside. Inside it is just to easy to hit a target and never go more than 10% up or down.

I've also found making it a point to move around and stand every 5 minutes when riding indoors helps quite a bit with getting your power vs. PE closer to outside. Sitting in one position for to long is unnatural compared to how much outdoor cornering and hills make you change position. I even do this on my 20 min tests indoors and do better.

kv501

^This x 1,000.

ZeCanon intervals at identical wattages are death for me indoors. Absolute torture.

Outside, it hurts, but it's a "hurts so good" kind of pain that's at least tolerable.

clones2

This is a TT bike and full aero setup - My #'s show on relatively flat sections that 24.5mph is between 260 and 275 watts...

The same watts on my road bike setup is about 2 - 2.5mph slower... The comment about the 1hr 40k was just for others to reference or gauge my experience or fitness, and is unrelated to the main question about indoor and outdoor power discrepenacies

Anyway - thanks for all the insight so far.

achoo

I also tend to think trainer workouts are different from outdoor rides.

Outdoors, power output can be much more variable, up to and including zero output for significant time. On the trainer, there are no breaks unless you explicitly take one - power can be steady within +/- 5% or even less.

That seems to make for a significantly different workout.