Using power for racing

you cant flat line your power any more than you can flat line your heart rate when on the road, just bare in mind that for any time you spend above threshold, you'll likely need to pay back that overstretch at some other point on the course. in fact that may well be your strategy...spend more power on hills and headwinds and repay the effort when its easier for a faster average speed.

thats assuming you're talking about time trialling, if its road racing then best advice is to ignore what you see and try not to get too alarmed when the power requirements go from coasting at 150 watts to 400 watts for 5 mins!

beldon said:

Got my first race of the season tomorrow. As i`m new to the power game I have been surprised just how much it fluctuates when on the road 😕

I am going to try and race a 10 mile TT at about 320/330 watts on my srms but how the hell do you keep it somewhere near when you are trying full on!

Anyone got any tips or is just try and see what happens

Thanks

I did my fist 10mile TT a few days after getting a PT, and having used a Tacx Flow turbo beforehand, had some recalculating to do due to the output discrepancies. That said, I did the 10 at too high a power which lead to a decrease in my power output over the 2nd part of the course. The good thing was being able to evaluate the event afterwards on CP.
Robkit's point about variable power pacing is something I've integrated into riding and training for TT's, and I think it is an essential consideration, although it is very independent upon each course and the weather conditions on the day.
As far as keeping an eye on your output whilst riding, even though the output is up and down, it is possible to get an idea on your power output by getting used to the 'feel' of the power your using. I plan to use my PT throughout this season on all my 10's and 25's as I find it more useful for pacing than not having one to look at.
Next weekend, I have a 2-up 20mile TTT, and I am very interested to evaluate the event to get an idea on my output in a lead postion and as a drafter.

AndROOb said:

Next weekend, I have a 2-up 20mile TTT, and I am very interested to evaluate the event to get an idea on my output in a lead postion and as a drafter.

I'd be very interested in hearing about (or even seeing) that! Please do post your insights after you've had a look at the file. And if you'd be willing to attach the .csv file, I'd love to look at it too.

I'm about 3 rides into my new PT Pro - they've all been indoors on the trainer (too much snow outside right now) but I can't wait to get outside and see the effects that terrain and wind have on my rides and power values.

Cheers,
Pad

beldon said:

Got my first race of the season tomorrow. As i`m new to the power game I have been surprised just how much it fluctuates when on the road 😕

I am going to try and race a 10 mile TT at about 320/330 watts on my srms but how the hell do you keep it somewhere near when you are trying full on!

Anyone got any tips or is just try and see what happens

I have had my PT SL for ~9 months now and (for lots of reasons) have spent a lot of time on my training rides attempting to precisely manage power. It is not easy, but here's what I have found works best for me. First, I set up my on-bike computer for the shortest averaging interval for all four functions (watts, speed, cadence and HR), because I want to know my numbers real-time rather than averaged. Second, during the ride I manage power through managing cadence. Typically, I ride in the general vicinity of ~100rpm and ~300w. So, each rpm translates to ~3w, plus or minus a bit. Road grades and wind gusts cause power to fluctuate quite a bit and I don't try to chase watts all over the place. I'm more interested in keeping my cadence smooth and my effort constant. When the grade or wind changes, I choose a gear and settle into my cadence. Then, I'll glance at the watts readout to get an idea of where I am. If I'm within ~30w of my target, I'll adjust my cadence. If I'm more than 30w off my target, I'll change gears because my gear spacings are typically in the 5-10rpm range. I find I can manage my cadence with much more precision than I can manage power.

RapDaddyo said:

I have had my PT SL for ~9 months now and (for lots of reasons) have spent a lot of time on my training rides attempting to precisely manage power. It is not easy, but here's what I have found works best for me. First, I set up my on-bike computer for the shortest averaging interval for all four functions (watts, speed, cadence and HR), because I want to know my numbers real-time rather than averaged. Second, during the ride I manage power through managing cadence. Typically, I ride in the general vicinity of ~100rpm and ~300w. So, each rpm translates to ~3w, plus or minus a bit. Road grades and wind gusts cause power to fluctuate quite a bit and I don't try to chase watts all over the place. I'm more interested in keeping my cadence smooth and my effort constant. When the grade or wind changes, I choose a gear and settle into my cadence. Then, I'll glance at the watts readout to get an idea of where I am. If I'm within ~30w of my target, I'll adjust my cadence. If I'm more than 30w off my target, I'll change gears because my gear spacings are typically in the 5-10rpm range. I find I can manage my cadence with much more precision than I can manage power.

Nice one. I will try that one. The TT all went wrong for me anyway. I`ve had a bad cold all week and spent the days before in bed. I was about 30 watts down on the average power for the 10 miles and was beaten by people I would normally beat or be close to. However, it was quite interesting. I tempered my start as I have a tendency to go off far too hard and die later, but when I downloaded the srm`s it showed my first 40 secs at above 700 watts! No wonder i die. Need to take a bit more off i suspect. 🙂

The power was all over the place and within a few seconds was showing from 250 watts up to 400! I`m sure it will get easier to manage but I`m beginning to wonder whether its worth racing on them after all

beldon said:

I tempered my start as I have a tendency to go off far too hard and die later, but when I downloaded the srm`s it showed my first 40 secs at above 700 watts! No wonder i die. Need to take a bit more off i suspect. 🙂

At the start of a TT, even a training one that doesn't really matter, you'll be amped out and at the gun will have the tendancy to go way hard. And when you do, the first 90 seconds or so still won't "feel" hard. But that initial effort will hurt you later on.

Next time try rolling out EASY... like leaving the coffee shop on the sunday ride. bring the power just up to the threshold you want to maintain, and DON'T GO OVER IT (at least for a flat TT... something with hills may warrant the "go hard up, go easy down" approach).

Finally, I disagree with RapDaddyo about the averaging, at least for a tt. Where your effort is relatively constant, having the averaging set at a relatively long duration (I like ten seconds) will really help you pace yourself. If it's jumping up and down 30 watts with every pedal stroke, it'll be VERY hard to really tell what kind of average you are putting out, especially in a TT, where you are supposed to be working at threshold.

beldon said:

The power was all over the place and within a few seconds was showing from 250 watts up to 400! I`m sure it will get easier to manage but I`m beginning to wonder whether its worth racing on them after all

This is common. I think (precise) power management is an acquired skill, but the skill can be acquired on training rides. Some on this forum believe they can manage their power without a PM. Maybe they can, but their skill does me no good whatsoever. In a TT, power management is what it's all about and for courses with lots grade and wind changes the optimal power management strategy is not at all obvious. Based on some testing I have done, I think optimal power management in a challenging TT (with grade and wind changes) is worth more than any single piece of aero equipment (wheels included).

Thanks again. I will try and start easier but it just feels so alien to not fly out as hard as possible.

One of my team mates was telling me about how he set off so slowly (to his average power) once that a woman vet beat his time for the first 1/2 mile! He ended up with a PB, so I know it works.

Just need to work out to permanently show the average watts on the srms now

Just pick a range of about 30 watts, with your goal in the middle. Let's say you want to average 330watts. Keep a range of 320-350watts. The more you ride with a powermeter, the easier it will be to maintain that range. It's ok if you spike near 400 for a few seconds, just be sure to let it come back down, or you will pay! Also, take into consideration the terrain. With the same effort, power will always be higher on uphills than downhills. So ride the downhills 10% below target to recover a bit. And allow a few more watts on the hills.

beldon said:

Thanks again. I will try and start easier but it just feels so alien to not fly out as hard as possible.

One of my team mates was telling me about how he set off so slowly (to his average power) once that a woman vet beat his time for the first 1/2 mile! He ended up with a PB, so I know it works.

Just need to work out to permanently show the average watts on the srms now

Beldon what was you average power and what time did you do? What was the course like and was it windy?

I did the NRHR and did a 1:11:14(1:14:14 inc 3 min late start) anyway I averaged 230 watts over 25 miles, my NP(normalise power) was 250 watts, whatever that means. I roughly calculated Hutch would have averaged 340 watts and NP of probably 375 watts. Did Blair Buss have SRMs on? If so do you know what his average power was?

Thanks,
Brian.

padawan said:

I'd be very interested in hearing about (or even seeing) that! Please do post your insights after you've had a look at the file. And if you'd be willing to attach the .csv file, I'd love to look at it too.

I'm about 3 rides into my new PT Pro - they've all been indoors on the trainer (too much snow outside right now) but I can't wait to get outside and see the effects that terrain and wind have on my rides and power values.

Cheers,
Pad

Hi Padawan,
here's the file from the 20mile TTT I did yesterday. There is a pattern to the lead/draft positions, although it's not that clear. I found that in the lead position, I was averaging 250-300w most of the time, and in the drafting position, between 180-220w. My NP over the 20 miles was 235w(I think), and our official finish time was 52:17. Not too bad for the first event of the season, I've got another 3-up TTT during april, and look forward to analysing the file when that's completed.
The file is a CP file, let me know if you need the PT(csv) file.

AndROOb said:

Hi Padawan,
here's the file from the 20mile TTT I did yesterday. There is a pattern to the lead/draft positions, although it's not that clear. I found that in the lead position, I was averaging 250-300w most of the time, and in the drafting position, between 180-220w. My NP over the 20 miles was 235w(I think), and our official finish time was 52:17. Not too bad for the first event of the season, I've got another 3-up TTT during april, and look forward to analysing the file when that's completed.
The file is a CP file, let me know if you need the PT(csv) file.

just tacking on a comment that I've been meaning to post for a while regarding the PT, sampling and the resultant reported power. Beerco is the expert on this sort of thing but I'll give it a stab ...

THe PT effective sampling period is 1.26 seconds -- that's pretty long compared to a typical crank cycle period of say 90 rpm or 0.666 seconds. It's also not SYNCHRONIZED to crank speed as is the SRM. As the sampling period randomly 'sees' more or less of the high-power crank cycle (and that's highly non-linear), instantaneous reported PT power can vary a LOT. My main point is that the PT will report variation that doesn't exist!

In Hunter and Andy's book, this is explained quite well ... as are most things 🙂

If using a PT, I would highly^3 recommend using at least 3-sample averaging on the display .. perhaps longer as some have indicated.

Another 'trick' for intervals is to set the Watts display to average power mode -- not sure I'd try that in a TT though - ideally I would love to have both live and average power data displayed. That would be superb for intervals or TT'ng. Yeah I know the Ergomo has it already ... but I have too much investment in PTs and SRMs at present. It's too bad we can't reformat the SRM display to display AP in place of HR. I find HR is just a darned distraction on the main display.

Re HR and cadence settings, I left them at (IIRC) the 5-sample default rate.

ymmv.
rmur

rmur17 said:

THe PT effective sampling period is 1.26 seconds -- that's pretty long compared to a typical crank cycle period of say 90 rpm or 0.666 seconds.

I agree that this is the PT computer recording interval. Is this also the actual strain gauge sampling rate or are the strain gauges averaging over multiple observations before the transmission? Speaking of which, does anybody have the specs on the PT strain gauges --mfgr, model#?

RapDaddyo said:

Is this also the actual strain gauge sampling rate or are the strain gauges averaging over multiple observations before the transmission?

IIRC, the hub transmits data to the receiver and hence to the handlebar computer at a frequency of several hundred Hz. The handlebar computer then has the task of averaging this data and performing the necessary calculations. The 1.26 s recording interval is therefore not an inherent limitation of the hub, but is actually the result of the limited memory capacity of the original PowerTap (I kid you not: apparently they arrived at 1.26 by dividing the available memory by the length of the longest ride they wished to record).

acoggan said:

IIRC, the hub transmits data to the receiver and hence to the handlebar computer at a frequency of several hundred Hz. The handlebar computer then has the task of averaging this data and performing the necessary calculations. The 1.26 s recording interval is therefore not an inherent limitation of the hub, but is actually the result of the limited memory capacity of the original PowerTap (I kid you not: apparently they arrived at 1.26 by dividing the available memory by the length of the longest ride they wished to record).

I *think* but am not certain, that the hub takes 60 records per second, which the h/bar computer then averages.

ric

ric_stern/RST said:

I *think* but am not certain, that the hub takes 60 records per second, which the h/bar computer then averages.

This makes sense. I can't conceive of why the strain gauges would sample as infrequently as once per 1.26 seconds.

ric_stern/RST said:

I *think* but am not certain, that the hub takes 60 records per second

Yeah, that sounds right...it's the SRM that samples at a few hundred Hz (two, to be precise).

acoggan said:

Yeah, that sounds right...it's the SRM that samples at a few hundred Hz (two, to be precise).

And, can't that data be recorded with the torque cable extra?

ric

ric_stern/RST said:

And, can't that data be recorded with the torque cable extra?

ric

Yes, I believe that the version of the PowerControl with the output port simply "streams" the raw data to the special SRM software running on the desktop/laptop computer. 'Biker-linz' might be a better person to ask, though, as I've never actually used an SRM system with this option.