Normalized Power & Perceived Exertion

frenchyge

I've had my PT for ~3 weeks and I've played around a bit and gone on some group rides with it to get an idea of my typical power outputs. On 2 occasions I've completed group rides and later found that my max 60-min normalized power (using Cycling Peaks) was 290W, and on a solo ride I've seen 287W normalized power for 1hr 20min. In both of these cases, the average power was much lower (244W and 220W, I think) than the normalized power because of the rolling terrain in this area, but I'm interpreting this data to say that I should be able to hold ~290W for 1 hour on flat terrain, or an indoor trainer. Is that right?

In any case, I wanted to do a full 1-hr test to confirm this assumption and set an official FT baseline, so I jumped on the trainer last night with the intention of starting at a ~300W pace and riding for 1 hour. Well, about 4 minutes into the test my glutes are burning ( ) and I'm thinking that there's no way I'm going to be able to hold this for an hour, so I drop down to about 280W. Another 3 mins go by and my quads are also sore now, so I'm trying to pump myself up to at least complete a 10-minute interval at this rate before quitting, dejected. Average power (and NP) for the 10-min interval was 287W, and I found a hard 20-minute interval on last Saturday's ride where I averaged that same power.

A couple of things concern me: 1) 300W on the trainer felt a lot harder than the same output on the road, and hurt my legs in different places(?) 2) Does RPE correlate better with NP or avg pwr? 3) Am I correct in assuming that I should be able to generate avg power on a trainer that corresponds to NP from an outdoor ride? 4) is there something about an indoor trainer (magnetic, in my case) that affects the readings on a powertap hub? I didn't do a torque-zero, but the watts did go down to zero when I stopped pedalling. 5) some trainers claim to have better 'road feel' but does that have anything to do with the relation between RPE and power output?

Of course there were other factors involved, so I'm not willing to give up on normalized power (low sleep the night before, trainer bike setup vs. normal bike, questionable food intake before the ride, trainer motivation, etc.) at this point, but that effort was pretty depressing compared to my expectations. I think I'd be lucky to hold ~260-270W for an hour based on what I saw last night. Comments?

acoggan

When the intensity is rated during exercise, perceived exertion is generally pretty accurate, although a certain percentage of all individuals have a hard time really cluing in on their body's signals (an expert in this area once referred to such subjects as "perceptual idiots"). What you're talking about in the first couple of cases, though, is your global sense of effort for the entire workout, something that Carl Foster has referred to as "session RPE". I don't know of any research regarding the precision/accuracy/validity of this approach, but suspect that it might be more variable due to its retrospective nature. For example, you might rate a ride that finished very hard as being more difficult than an equally-intense one that was more evenly paced, just because the final portion of the first workout was so fresh in your mind.

As for attempting to replicate your normalized power on a trainer and finding it painful, I am not all surprised. Many things are different when you ride indoors: there's no scenery, no riders around you to motivate you, heat stress tends to be higher, the intensity is absolutely unrelenting (at least on an ergometer), the "loading conditions" faced by your muscles (i.e., where in the pedal stroke you tend to feel more or less resistance) are different, etc. It is reasons such as this that we routinely required cyclists serving as research subjects in the laboratory to train on the ergometer a couple of days per week for several weeks before participating in any experiments in which performance was to be measured.

In any case, based on your normalized power from outdoor rides, I am quite confident that you could sustain 290 W (+/- 5%) for 1 h on the trainer, provided that you were sufficiently motivated to do so.

frenchyge

Thanks for the comments Andy. Your highlighted comment was particularly apparent last night. It has been a while since I've ridden on my trainer, but I was really surprised by the extent to which I had to drive over the deadspot at the top of the stroke just to keep the pedals from bogging down. I couldn't just hammer the downstroke like I was used to on the road.

Is 'trainer time' considered to be less effective than 'road time' for this reason? Trainer time sure feels hard because of the unrelenting intensity, but is some of that benefit lost because of the non-specific way in which the leg muscles are trained? I'm looking to upgrade my trainer this winter, so maybe I'll put more importance on the larger flywheel if that is the case.

palewin

Frenchyge: could you either include your weight, or provide some equivalent numbers in terms of watts/kg? While perhaps we shouldn't, I always try to compare the power numbers posted to my own, and end up wondering whether I should simply burn my USCF license, until I remember that most of the numbers aren't scaled to a 138-lb rider! Thanks.

frenchyge

35 yrs old, 6'1", 175lbs, riding for ~6 yrs (club rides, and century stuff), just started racing this year (Cat 5) but am one of the strong-ish Cat 3-5 riders on my current team. W/kg is 4.7 @ 5-min, 3.6 @ 1-hr.

Check this out for a better sampling comparison tool:
http://www.cyclingpeakssoftware.com/profile.html

jws

frenchyge,

Among what Andy said, don't discount the "heat stress" aspect, especially in summer. Most guys who ride the trainer in winter do it in a cold (5 deg C or so) room with multiple fans blowing.

Also, you may find a really comfortable position hard to obtain on the trainer. So, don't put too much emphasis on your indoor power unless you're going to train there a lot.

Jimmy

frenchyge

The trainer is in my basement (which stays cooler), and I had a box fan blowing on me during the ride. I was sweating a little, but not dripping.

I am planning to use my trainer a lot again this winter, but was just using it to find a 'flat stretch of road' last night. I was hoping to see a good correlation between road power and trainer power so that I won't have to re-calibrate all my zones for the trainer, and then back to road next Spring. In fact, part of my motivation for switching to power training was the expectation that I would be able to correlate my Winter training with my Summer training. That said, I was a little shocked at having gotten my butt kicked so quickly.

acoggan

I've trained extensively on various ergometers and trainers for about 20 years, and based on that experience I'd say that the answer is "it depends". (You just knew that was coming, didn't you? ) Specifically, I think it depends on the particular trainer, as well as the power output: when the inertial load* is much lower than that typically encountered outdoors, or when the power isn't all that high, then the difference between indoor and outdoor training may be significant (note the use of the word "may"). However, if the inertial load is high enough (even if it isn't nearly as high as outdoors), and/or you're working fairly hard, then things tend to converge and it really isn't a significant issue. Or to put it another way: I personally wouldn't obsess about finding a trainer that has a large inertial load, although given my druthers I'd pick one that has a good "road feel", if for no other reason that it is more pleasurable to ride.

To give an example: yesterday I did an incremental exercise test on my Velodyne (flywheel mass = 10 kg; inertial load approx. 2/3's of riding outdoors at the same "speed") during which the power was incremented by 25 W every 1 min. I lasted 15:10, with my MAP being 378 W. This morning I repeated the test, but instead of using the 53x14 I left the bike in the 39x23 throughout the test. The wheel and flywheel turned more slowly as a result, meaning that the inertial load/stored kinetic energy was less. It felt different, especially at the lowest power outputs. Nonetheless, when the going got tough the going...well, got tough, and I last 15:19, an insignificant difference. However, if I had done this test on my mag trainer, with its much smaller flywheel, I am sure that the difference in feel would have been even more dramatic, and my performance might have been affected.

Another example: back in January I did 1 h of 15 s on/off "microintervals" on each of three different trainers: my Velodyne, my mag trainer (a Minoura, BTW), and a Cyclops fluid trainer that I borrowed. (On three different days, of course.) Due to the differing characteristics of the three trainers, the quadrant analysis plots from these workouts were distinctly different, yet they all felt roughly equivalent to me. Combined with experiences such as the first example above, I therefore believe that the power you produce is the most important determinant of your physiological and psychological (perceptual) responses, with how you actually produce that power being much less important.

*The inertial load that you encounter is dependent not only on the mass of the flywheel, but also how that mass is distributed (mostly determined by size) and how fast the flywheel is spinning. You'll therefore get a more "road-like feel" if you use the highest wheel speed (and the heaviest wheel) that you can, and some people have even gone to the trouble of adding additional mass to either the flywheel or their wheel.

acoggan

BTW, for seated efforts I can't distinguish between the maximum power I can generate indoors or outdoors for any duration. Only when standing outdoors am I able to produce a bit more power than indoors, probably because I can use my upper body a bit more.

RapDaddyo

I don't have to spend much time on my trainer due to the weather conditions here, but I can absolutely relate to your experience. When I do get on my trainer (Tacx Swing), every power level >200w "feels" harder than the same power level on the road. I haven't done a correlation with HR, but it feels as though it is more effort on the trainer. As Andy says, if I did workouts on the trainer a few times a week for a few weeks it may well feel equivalent. But, initially at least, it feels much more difficult. Is your HR at 300w the same as on the road or higher?

frenchyge

I didn't wear the strap last night, but my breathing felt heavier. Outdoors, 300W feels like a fun-hard effort, whereas last night it didn't feel fun at all. When my glutes started hurting, I kept thinking "I'm going to be a laughing stock if I blow out my glutes too, like Rapdaddyo."

RapDaddyo

When I saw "glutes," I thought, "Oh, no!"

HammerHead

I dunno man. I train with a power tap, and those numbers look good to me.

I personally think the difference between trainer and outdoor riding is that when I'm indoor on the trainer - all I'm thinking about is how I feel. No scenery, no other riders to chase, no wind, nothin. Me and the pain. My heart rate is comparable vs wattage outside or on the trainer.

__________________
I'm only truly happy when I'm anaerobic.

frenchyge

Good point. That's definitely the case.

Thanks, I'm not dissatisfied with my numbers, but I was frustrated by not being able to reproduce my road efforts (according to the normalized power algorithm) indoors.