RPE (+HR?) vs Power for TTs - Page 6

My name is Andy so I feel obligated to reply

I'm certainly no TT expert (like the other Andy) but when I'm doing things well, I use the PM to make sure I don't go out too hard. I have a pretty decent anaerobic capacity but a pretty low threshold which can get me into trouble . So, for the first 5min, I have an upper limit target and try not to exceed it much.

For the next 50min I look at the PM from time to time - not continuously - to make sure I'm not slacking too much and have a lower limit target - my threshold - which I try not to go below unless I'm flying down hill or something (I use that as an opportunity to soft pedal). Mostly I regulate via RPE this way. For the last 5 min the PM is worthless because you're just burying yourself.

The one TT that I won was quite interesting I thought. It was very short - two laps of our local car racing circuit. There's a little hill once per lap. The plan was to use the PM to go "easy" on the first lap except for the hill, and then go balls out the second lap. I had an upper limit target (around 300w) for the first lap and didn't even look at the PM for the second (o.k. maybe I did).

Anyway, in spite of the plan, the first lap ended up around 325w and the second at around 306w. It's very very hard to not go out too fast. It ended up being o.k. as I won the tt by one second, but just goes to show you that even with tools it's difficult to do what you intend. I do imagine that I did better with the PM than I would have without it.

I echo this observation. And, if you look at my little TT test in an earlier post, my HR would have been of little value to establishing a pace for the first 2.5 minutes. I think if I didn't have a PM, I would have been dependent on RPE (and bike speed) to modulate my intensity in the first few minutes until HR stabilized. The problem is that we pay such a high penalty for going out too hard due the 4th power lactate/power curve. I think I'd go more by bike speed unless the first leg was upwind on a gusty day and then I think it'd be a total crap shoot.

I think that experienced riders (and you don't necessarily have to be elite, just have ridden hard over varying terrain enough to get a feel for your limits) generally already pretty much know how to best pace themselves. Indeed, if you take the powermeter files from various riders TTing the same course, normalize the data by expressing it as a percentage of their average power, and overlay the plots as a function of distance, what you'll find is a striking correspondence - basically, we all "give it some stick" and "float" in the same places (e.g., up and down hills). Nonetheless, I do view TTing with a powermeter useful even in such non-steady-state races, as it 1) prevents you from starting out too fast (an all-too-common mistake, even among experienced riders), 2) gives you constant objective feedback against which to compare your subjective feelings, and 3) provides a "carrot" to chase when you feel like slacking off. That said, I don't think using or not using a powermeter in such events has a major impact on performance (except for preventing you from starting too hard), at least in those riders who have developed and trust their own perceived effort. It may, however, be really helpful to riders who haven't achieved the latter state. I think that this is more likely to be true of riders who "grew up" as a cyclist using a heart rate monitor all the time, and thus have been distracted/prevented from developing an accurate effort sense, and/or of individuals who simply tend to tend to overthink/overanalyze things (note: these comments are not meant to be directed at anyone in this thread, but are just general observations - so please, nobody take them personally).

FWIW, here are a few examples of my experience when TTing with a powermeter:

1) the first time I ever used one (a borrowed SRM) in a TT (which happened to be flat), I taped over the display and raced just on perceived exertion, as I have always done. Sure enough, when I looked at the data afterwards I learned that I had ridden the first handful of minutes at >10% over the the power I was able to sustain, despite the fact that it felt like I was maintaining a steady effort and despite the fact that I had >20 y of racing experience under my belt at the time.

2) fast forward a few years, and I used my then-new-to-the-market PT in a very hilly-to-rolling TT. I'm still keying off of perceived exertion, but make an interesting observation: the times that I exceed the power corresponding to my VO2max for a significant period of time when cresting one of the rises are the times when I feel like I "bog down" speed-wise afterwards, whereas the times that I just approach but not exceed that power are the times that I seem to be able to keep it rolling. IOW, my physiology, perceived effort, and actual performance all seem to correspond, thus vindicating (if you can consider it that...the scientific literature says that perceived exertion can be quite accurate) the use of perceived exertion. Nonetheless, having the powermeter providing objective feedback was still helpful, as in effect it allowed me to continuously recalibrate my perceived effort (as for heart rate, well, forget it: the response time was too slow for it to really be of any use).

3) a couple more years go by, and I'm racing a ~35 min TT the day after a hard ~3 h road race. My legs are absolutely dead, but I give it all I can anyway and end up with a respectable (for me) average power. My average heart rate, OTOH, was nearly 20 beats/min lower than usual!! If I hadn't had the power data, I would have been one of those guys running around after the race complaining "man, that sucked - I just couldn't get my heart rate up today!". Having the power data, however, I knew that I couldn't have really expected to go any faster, so didn't waste mental or physical energy trying to drive my heart rate up to its usual levels in the first few miles.

Great insight Andy (C.), thanks. One point that I wanted to comment on:

The only issue I see with using RPE is that, like HR, unless your senses are very finely tuned it only tells you *when you're already screwed.* In other words, by the time your legs 'bog down' you've already pushed too hard. Power, on the other hand, lets you be proactive in your pacing to avoid the negative effects of overshooting your bounds.

Just wanted to second that thought. Thanks Andy.

True, true - that was really my point by relating how I overshot my sustainable power during the first TT I ever did using a powermeter.

OTOH, powermeters have their limitations as pacing tools as well, especially during very short events, e.g., a pursuit. For example, while my wife always raced with one her last year of competing, she didn't rely on it for feedback during her speciality event - it was simply too hard to read and make sense of the jumpy power numbers when powering around the velodrome. In a situation such as this, I think the powermeter data are much more useful for post-hoc analysis, i.e., you do a ride by feel, then look at the power data to see where you went wrong and try to do better next time again by feel.

FWIW, I'm doing the pursuit at master track nationals in about two weeks. I'll have the SRM on my bike, but I only plan on looking at it once, to make sure I've hit the right speed/cadence going into turn 3 of my first lap. After that, I'll be relying on perceived exertion and split times to adjust my pace.

Great post, Andy. Obviously, you gave this a lot of thought. One sort of bottom-line question as it pertains to this thread. Let's say you are going to ride a new course in a 40K TT and you wanted your best performance. The course is a typical TT course, rolling, closed loop or out/back, with some wind changes. First, would you want your PM on your bike or would you be indifferent? Second, would you manage your effort primarily with perceived exertion, primarily with power, or a mix? Third, do you have a feel for the net benefit (if any) the availability of power data would have on your time?

[QUOTE=acoggan]good luck with your race(s) Andy. Remember to keep a tight line - every .. what 1.2 seconds? counts But you know that already ...

rmur