Power difference - indoor Vs outdoor

I am aware, from previous posts, of the various factors that may influence the reduced power output one sees when riding indoors. We have been doing a lot of work, however, with a few clients who have both PT on their road bikes and ride a PT equippped PT300 trainer indoors.

The differences we are seeing in 2x20 sessions is as great as 40w.

Given that most of these riders do their on road 2x20 sessions on a climb, do you think there is any merit in the theory that if they were to do the road sessions on a flat course, that the power differential would be less due to the fact that putting out power on a flat course is more akin to putting out power on a PT300 ?

If not then all I have is the lack of practice these guys have on the indoor machine to account for such a large differential (requiring 2 separate FTP figures in CP)

Any thoughts greatly appreciated.

I would expect this difference to narrow as they gain experience riding at high intensity indoors. I'd be interested in seeing if there is a difference after, say, 8-10 trainer sessions.

OK - but what about the smaller variance between trainer & flat road versus hill road sessions - does this hold any water?

The logic is that it is easier to get your power up on a climb and so this makes trainer riding closer to flat road riding where it is more challenging to get power up.

I think what makes it easier to produce a given power on a climb versus the flat is the concentration required. On a climb, with a more constant resistance, we don't have to concentrate as much because there is resistance on each pedal stroke, even if the resistance changes slightly from stroke to stroke due to slight grade or wind changes. We can be mentally lazy and count on having something to push against. On the flat, the grade or wind changes can cause the resistance to virtually disappear and we have to immediately increase the downstroke velocity to compensate for the sudden loss of resistance. This requires much more acute concentration to keep power up. But, from a physiological adaptation perspective, I don't think there is a difference between riding uphill and on the flat at the same constant power. So, from a concentration perspective, I agree that riding a trainer is more like climbing in that it is mentally easier to maintain a given power.

P.S., I just realized that you said you thought trainer riding was more like riding on the flats than climbing. No, I disagree, I think it is more like climbing due to the more constant nature of the resistance.

I have to agree with you - riding with a steady and smooth resistance on a PT300 is akin to a climb. The argument being presented to me is by somebody who struggles to match their 2x20 power on flat roads in a big gear (also steady effort) and as such feels that this is what riding the trainer feels like to him. His power on the big gear flat ride is closer to his PT300 ride.

I think it's something different: riding the trainer sucks. It's boring. It's hot, even with good fans (and I assume your riders are using good fans, right?).

Most competive riders start out as recreational riders and make the jump to competing because they enjoy riding bikes. Being outside, with the wind in your face generally beats riding a trainer by a large margin.

Don't get me wrong... I can now do just about (probably within 5%) of my outdoor numbers indoors on the trainer. But that's by watching the power meter and shooting for particular numbers and developing quite a bit of mental stamina. I've even become a bit of a sadist, preferring to ride the trainer for some workouts.

I'd say give them time... it takes some time to develop the mental toughness necessary to put out the same numbers indoors.

I would tend to agree but find that having done the tests myself, it is hard to put a 30-40 variance down to these factors. I can do a 290w 20 min on the road but literally cannot do more than 10 mins at a push on the trainer - HR and RPE indicate a higher physilogical strain - can this really be just down to mental toughness - I don't think so.

It has to have something to do with the mechanism of pedalling at a very steady resistance with no momentum ?

On a climb I am under and over my goal power regularly but on a trainer it is just like riding through mud.

How long have you been working at it? Jumping on and believing that the session will be impossible to finish can be a self fulfilling prophecy. When I've got a difficult goal number to hit, sometimes I'll start the first 3-4 minutes at what I know is achievable and work my way up to the goal number.

Physiologically, what's your cooling setup like? Honestly, you cannot have too many fans. Doing these in a stuffy room with no air circulation would be a killer.

I think this is a common initial experience, but the difference narrows with experience. There is a post from Andy C. to this effect on one of the threads about trainers. IIRC, when they do trainer-based testing, they have the test subjects ride for some number of weeks on a trainer to adapt. After a period of adaptation, I think they have found no difference in the power a subject can generate on a trainer vs. outdoors. I think frenchyge found this as well when he began riding a trainer this past winter (out of necessity). I find that my HR is similar on a trainer at the same power as outdoors and that the main issues are overheating and concentration.

One more note... I absolutely positively need something to take my mind off of the effort when I'm doing hard workouts on the trainer. Movies can be good, but believe it or not, I've found audiobooks to be the best. Listening to a fast paced audiobook forces me to take some of my concentration and focus it on building the story in my mind rather than my natural point of focus, "this sucks, how long till it's over." I've actually even extended an interval or two in the past because I want to get to the end of a chapter.

i can generate >20% power *indoors* on a trainer, while suffering like a dog in the heat with one average fan, being bored out of my brain. i wish i could generate more outdoors.

(and yes, it's the same Power Tap, and i have the same experience with an SRM, and my HR is higher outdoors!).

My outdoor hour power, i can maintain indoors for 3-hours (assuming i don't die of boredom!).

And, i hardly ever ride the trainer these days!

Ric

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25 watts more outdoors (20 min) mostly cuz I dont fall asleep

i'm thinking even the most steady hill or flat course can't come close to approximating the steady unwavering pace you can attain on a set of rollers or a trainner.

I tried doing an hour at FTP last week on a fairly flat course, i found it hard to keep my power between 200 and 300w. On the rollers i can usualy just pick a gear and cadence then cruise along for an hour watching tv and me PT graph shows no more then a 10w variation.

I menchain this because having small spikes up and down around your FTP can definitly influence how much energy you have for the rest of the interval.

Say for example, 5 mins into your first 20min, there's a very short, but steep rolling hill, like not even 30meters, and you decide to just power up it, and end up pushing yourself up to 450w for 10 or 20 seconds, HR goes up, cadence goes down a tad, then you settle back down to your FTP of 260w. Even missing slight grade changes like 1% can push my power up to 320 or 330w without me even noticing. Not to menchain going down the other side of a slight slope i always have to be aware that i'm keeping my power up over 200w, cause my natural tendency is to glass crank it a bit and recover.

There's also hopping out of the saddle to avoid bumps, dips, cracks, pot holes, the nervousness and anxiety of dealing with cars, worrying about getting a flat, trying to watch the road but also your power read out.... etc

Once you factor in all those real world scenario's it's easy to see how you could prematurely weeken your legs if you're trying to do a steady 260w ftp 2x20.

One last though, indoors you can pretty much carve your cadence in stone where being outside changes in cadence or having a completely different cadence cause you're doing your FTP workout on a hill can skew results quite a bit too if you're not in your more efficient cadence range.

There's a hill around here i climb at 400W takes about 2 and a half mins if i pace myself for 10 repeats. and i'm pretty dead once i'm done # 3
On the rollers i can hold 400w for over 4 minutes 5 or 6 times in a row cause there's no changes, accelerations(bumps) my legs have to work thru it's completely steady and a continuous load, and i'm at my optimal cadence of 95-100 the whole time instead of 80-90 which is usualy what i do when climbing in the saddle.


Just my experience though.

That question has puzzled me for a while.

My power on the trainer was much lower than on the road. I realized that it had something to do with a) cadence and b) variability.

I also agree with the cooling and motivation effect.

For the whole winter training (indoor), I was maintaining 100-103 RPM. On the road, I quickly realized that I could generate more power more easily at a cadence of 92-96 RPM.

In fact, being relatively new to training with power, I find that learning to find sweet cadence zones depending on the conditions has been a great benefit so far.

The variability of the cadence also help it seems.

I don't think that logic holds water. 2 weeks ago I did a stage race in Arkansas which featured a couple difficult climbs, unlike any to be found here in Kansas. The Mt Nebo climb was 2.5 miles at an average grade of ~11%, and I was thinking that this would certainly set a new best 20MP because I never have an opportunity to climb for 20 minutes straight. We raced 35 miles flat to the base of the climb, and then 2.5 very difficult miles up extreme switchbacks. Looking at the power file post-race, I found that my power on that 20min was within 5w of what I would see for a hard effort on a flat course. That's just a personal observation, but it's enough for me to question whether 'climbing' in general really allows for more power, or whether people just tend to push harder on climbs that aren't terribly long.