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Power Meters for Dummies

 
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JaRok2300




Joined: 01 May 2014
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Location: Worcester, UK

PostPosted: Fri Apr 28, 2017 7:51 am    Post subject: Power Meters for Dummies Reply with quote

I finally took the plunge and picked up a used Powertap G3.

I've read a fair bit about FTP and the various training percentages for given intervals etc which I have been using on my Bkool/Golden Cheetah over the winter.

What I haven't really found much about is the real basic stuff like what metrics do you have on your head and what would you monitor.
On a shorter ride I'm thinking I'd recreate the interval type sessions I've been doing on the turbo but on longer 2/3 hour rides I'm not so sure.

I guess instant power would be too erratic so 3s or 30s might be better and then some sort of variability metric may be useful too. I've got a Garmin 910 & 705.

Thanks for any advice.
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Jorgan




Joined: 12 Nov 2007
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PostPosted: Fri Apr 28, 2017 9:27 am    Post subject: Reply with quote

You can customise your head unit screens to give you all sorts of data. On my Edge 500, I have 4 screens (one is for when I ride without power metrics). Certainly for racing, you need to pay close attention to things like IF (Intensity Factor or % of FTP), TSS (Training Stress Score) and Normalised Power (NP).

- IF will tell you if you're pushing your ride/race too far beyond your threshold, or in training that you can (or need) to go harder.
- TSS is essentially how many matches you've burned (are you exceeding your planned outlay of 'work')
- NP is black magic that tells you again if you're pushing too hard (like IF)

Lots of training rides will give you targets for the above power metrics come race day. I use a 920XT, but the Edge is also there right in front of me with more data.
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Aldo




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PostPosted: Fri Apr 28, 2017 11:37 am    Post subject: Reply with quote

On my display I have 3s averaged power (less noisy but still good indicator of current effort) and average power for the total ride. NP is worth having too as the higher NP is relative average power, the more you are surging effort. On a flat course, NP and average should be very close but on a hillier ride this is harder to achieve.

One of the best uses for me is to stop me pushing too hard up hills, or at the start of the race it stops you getting carried away
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Cat5 in the Hat




Joined: 14 Mar 2011
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PostPosted: Fri Apr 28, 2017 5:00 pm    Post subject: Reply with quote

For easy training I have 3s avg power

For interval work I have 3s avg power and lap average

For TTing I have avg speed, current speed and time. No power showing.

Buy a copy of Training & Racing with a Power Meter by Coggan & Allen.
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JaRok2300




Joined: 01 May 2014
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PostPosted: Mon May 01, 2017 7:32 pm    Post subject: Reply with quote

Oh well, that was easier than expected.
705 doesn't support any of those fancy metrics so 3s power it is then.
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hammerer




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PostPosted: Thu May 04, 2017 10:45 am    Post subject: Reply with quote

On mine I have 3sec power then cadence underneath. The 3rd line I have speed and HR 4th line 30sec pwr then have "30sec" l/r balance next to it

distance and time on screen 2 with a couple other things
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Chrace




Joined: 28 Apr 2010
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PostPosted: Fri May 05, 2017 3:06 pm    Post subject: Reply with quote

At IM Copenhagen I used a screen with only 3s avr power. The only thing I monitored was whether I went too high (or low, the slacker). My logic was merely that it doesn't matter what speed I am at, only what effort I am producing to avoid blowing up before the run.

The second screen had distance to go, but still no time. I didn't want it to mess with my head and try hit an "X bike split".

For training I generally have 3s avr as big as I can, then time/distance followed by clock time and speed. I seem to remember the 705 can do this quite nicely.
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jibberjim




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PostPosted: Fri May 05, 2017 4:00 pm    Post subject: Reply with quote

I'm interested in the 3s avg people, there's already a 2-3second lag on the power, so with 3s avg you find a change in power "now" not really impacting the number significantly for 5s, does that not lead you to start tail chasing the power and wildly fluctuating anyway, exactly what the 3s (to avoid aliasing effect) is attempting to discourage?
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Jorgan




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PostPosted: Fri May 05, 2017 4:48 pm    Post subject: Reply with quote

I don't get why people don't just use IF & NP to mete out their effort.
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Chrace




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PostPosted: Sat May 06, 2017 7:02 pm    Post subject: Reply with quote

jibberjim wrote:
I'm interested in the 3s avg people, there's already a 2-3second lag on the power, so with 3s avg you find a change in power "now" not really impacting the number significantly for 5s, does that not lead you to start tail chasing the power and wildly fluctuating anyway, exactly what the 3s (to avoid aliasing effect) is attempting to discourage?

Not really. I'd say I could use 30s average for most scenarios since that's about the rate I look down anyway. But that's not what I use it for.

I mostly check on power when I can feel I am starting to push. Then I check if I am overdoing it and need to ease off, or whether it's just me getting tired. I don't ride and look down all the time, making current/instant power fairly useless since it fluctuates a lot (for me anyway). Some smoothing is required I feel.

Similarly, I check when I feel it's going easy but I can see I am flying. Then it might be me who's starting out too hard and need to ease off.
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Chrace




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PostPosted: Sat May 06, 2017 7:04 pm    Post subject: Reply with quote

Jorgan wrote:
I don't get why people don't just use IF & NP to mete out their effort.

The 705 doesn't have IF and NP.

I missed it back then, or at least I thought I did. Then I switched and did more Triathlon X style stuff where IF is a goner anyway. NP is kind of useful, but 3s avr works best for me on the hills to cap effort (or simply know when I am burning matches).
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