Functional Threshold Power Outdoors and Indoors

harringtonp

Hi Guys,

Noticed that when doing interval workouts, I can hold the same wattage for an interval outdoors much easier than on an indoor trainer, perceived effort feels less and heart rate average for the interval is lower.

Also when building a power profile I noticed that I can get best values on a decent hill so a 5 or 20 min test on a hill will give a higher average than on the flat.

Did some googling and this is quite a common thing, most people with PMs report it being harder indoors than outdoors though you do come across the occasional person who claims the opposite.

Anybody here have ideas as to why this is the case ?

couerdelion

Outdoors you have a cooling breeze, indoors even a fan can't really replicate that.

harringtonp

couerdelion wrote: »

Outdoors you have a cooling breeze, indoors even a fan can't really replicate that.

Does that account for 15-20 Watts ?

Diarmuid

First what PM do you use? With the Power2Max once you heat up the room a few degrees (body head) you have to freewheel to allow it to self-adjust.
Apart from that, I'd agree that it's mostly down to the airflow plus the mental aspect (boredom of sitting on the turbo). I don't know anyone who doesn't find it harder to hold the same power on the turbo that they can on the road.

harringtonp

Diarmuid wrote: »

First what PM do you use? With the Power2Max once you heat up the room a few degrees (body head) you have to freewheel to allow it to self-adjust.
Apart from that, I'd agree that it's mostly down to the airflow plus the mental aspect (boredom of sitting on the turbo). I don't know anyone who doesn't find it harder to hold the same power on the turbo that they can on the road.

Use a power2max and generally never worry about calibration with it, just pedal away... they do claim after all it self calibrates and nothing specific is needed. However unlike an outdoor cycle where one always free wheels at times (and the PM presumably recalibrates) in a turbo session once I start pedaling I generally don't stop until the session ends. So next time will stop pedaling for a few seconds after warmup and just before first interval.

I doubt though if the PM readings are the problem, they have always seemed consistent and I have had reason during the odd indoor session to stop pedaling momentarily.

This blog

http://alex-cycle.blogspot.ie/2009/01/turbocharged-training.html?m=1

gives some reasons and he has cooling top of his list, I would have thought inertial load would play a bigger part, particularly when you start wondering at what points strain is measured in the strain gauges in the PM.

Also on a turbo one can and does tend to hold power steady for an interval. If doing the same interval on a hill I find you get out of the saddle on ramps, generate a power way beyond the interval target for some seconds and then sit down and are able to continue more or less at the level you were previously at.

These spikes help push the average up, its like you dip into the neuromuscular process for a short time without it detracting from your ability to maintain the steady power. Anyone else have comments or observations on this ? Or is the line of thought total b****...

Lumen

As discussed in the recent climbing thread, inertial load is lower on hills (at lower road speed), as is cooling.

But lots of people claim that they can generate MORE power on hills than on the flat.

So if a turbo shares the cooling and inertial load characteristics of a hill....

niceonetom

Do people see the same discrepancy when using rollers instead of turbo? That'd separate out the inertial load difference from the psychological weakness.

Beasty

Personally I find it easier to do the short/high power efforts on the Wattbike - my highest power output on that is over 1,300w, my highest on the roadbike is quite a lot less than 1,200w - however they are not directly comparable - the WB measures more accurately based on complete pedal revs while the bike PMs do it by the second. In addition it's a lot easier to hit the "sweet spot" on the WB

Moving onto zone 6 stuff - 3-6 mins or so, the WB performance retains the edge except in the hill climb scenario where I have put out a bit more power

For longer times I think the enviromental and psychological issues tend to dampen indoor performance. Outside you do have the fresh air and more distractions to take your mind off the pain. However even having said that my personal performances on the WB over this winter have been far superior to those on the roadbike for all "distances" I have been prepared to grind/spin it out on the WB (up to just over an hour). That's because every WB session has a purpose and I will usually be trying and hit targets/improve PBs. On the roadbike there are more variables, particularly opportunities to ease off on a downhill or having just put a bit of effort in on a climb (which is where NP starts to be a bit more representative of overall effort)

The only time I feel I can push it as hard as I can on the roadbike is in TTs - again on hill climbs I will typically outperform the WB power. However for flat TTs you actually lose some power due to being in the aero position - I reckon that probably reduces threshold power by up to 25w or so. If I look back at my 10m TTs over the summer that would be about the reduction in power compared to what I have done over 20 mins on the WB in recent weeks. Hence looking at it that way I'm probably matching performance indoors and outdoors over that time period

harringtonp

Interesting observations. With the large fly wheel on the wattbike I would expect that it would be very similar to a road bike in flat calm conditions in terms of how it feels to hold comparable wattage for comparable time intervals.

Before getting the power2max I was doing power sessions on a Sports Art Gym bike and when I moved from this to the turbo trainer/PM setup I noticed a small reduction in power. I assumed that it was that the gym bike was uncalibrated and just threw out a watt figure just to keep punters happy. It has a large flywheel and I am not so sure now. It may well have been calibrated and I suspect RPE and HR on it for a given wattage might be similar to that on the PM when cycling on the flat outdoors.

I don't really buy the airflow thing as I've done some turbo sessions outside in freeze your balls temperatures and it still feels harder. And if riding intervals on a stinking hot day I would also expect higher RPE for given wattage than on a normal temperature day.

While the psychological/boredom aspect definitely does make turbo sessions harder it does not explain the higher HR for holding the same watts in an interval.

As all my training sessions that count over the winter (Sunday spin is the one "easy" one and is) are done on a turbo, my zones are based on a field test on the turbo. If doing similar sessions outside when weather is better I'll use a field test from outside. In fact it could make sense to have 2 outside field tests if you want to take it to extremes, one during a flat time trial (using a road bike !) and another on a hill. Then depending on whether you are doing flat or hilly intervals you use one or the other

couerdelion

Cooling is a big thing I believe. Sat outside in a stationary position albeit in a cold temp won't have the same effect as ride along when convective cooling takes place. Think of it like this - place a can of beer on your windowsill in a wet sock and go back 5 mins later - probaby won't have cooled much - hang it outside the car window whilst your moving along - it will be lovely and cool 5 mins later. That just IMO anyway.

Friel has some ideas too - http://www.joefrielsblog.com/2011/01/indoor-vs-outdoor-bike-performance.html

harringtonp

couerdelion wrote: »

Friel has some ideas too - http://www.joefrielsblog.com/2011/01/indoor-vs-outdoor-bike-performance.html

That is well worth the read, in particular the comments from users. A heap of suggestions and possibilities are thrown up. Bottom line I gather from this and other stuff I read is that nobody really knows for sure. Could be a great PHD for somebody academically minded to take on.

harringtonp

Beasty wrote: »

The only time I feel I can push it as hard as I can on the roadbike is in TTs - again on hill climbs I will typically outperform the WB power. However for flat TTs you actually lose some power due to being in the aero position - I reckon that probably reduces threshold power by up to 25w or so. If I look back at my 10m TTs over the summer that would be about the reduction in power compared to what I have done over 20 mins on the WB in recent weeks. Hence looking at it that way I'm probably matching performance indoors and outdoors over that time period

Dragging this up again as recently did a threshold session on the turbo on a TT bike with 3x12min intervals where within each 12 minute interval I alternate 2 minutes between very slightly under threshold and over threshold. Usually do these turbo sessions on the road bike, this time started on the TT bike at the same levels but quickly found I was blowing up. So for second and third interval had to reduce by 30 watts to get me through it. Noticed also that physiologically HR was about 5 beats lower, lactate in the legs was the limiting factor.

Was surprised at how large the difference was and was wondering if training in the TT position could reduce it by much ? Or is that just how it is.

BTW best wishes for a speedy recovery Beasty.

Beasty

I know one top cyclist in Ireland who reckons he loses 25w or so in the TT position. I think my power loss is pretty similar. Of course you make up more "real" time as a result of being more aero

pprendeville

So what's your FTP in watts and HR. Also like to get an idea of where I'm at in comparison with others. Height and weight if I'm not being too cheeky as well.

godtabh

pprendeville wrote: »

So what's your FTP in watts and HR. Also like to get an idea of where I'm at in comparison with others. Height and weight if I'm not being too cheeky as well.

253 watt. 6ft 95kg. Would need to check hr

pprendeville

Cool. Cheers. That's a good workout which (over/under) which I must start using soon. Was reading a mag last year and Ian Stannard said he uses it a lot for the climbs.

mossym

harringtonp wrote: »

Was surprised at how large the difference was and was wondering if training in the TT position could reduce it by much ? Or is that just how it is.

.

can hit targets a lot easier on the road bike than the tt bike on the turbo, so don;t think what you are seeing is any way strange