Page 2 - Confused about setting Threshold Power

18-10.-2005, 12:03 AM

#16

acoggan

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Posts: 2,622

Re: Confused about setting Threshold Power

Quote:

Originally Posted by RapDaddyo

First, I'm not complaining about CP. I love it.

1) Glad to hear it!

2) I didn't take your comments as a complaint - I just used them as an excuse to share some of the thinking that went into the program.

18-10.-2005, 12:16 AM

#17

RapDaddyo

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Location: Las Vegas, NV

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by acoggan

1) Glad to hear it!

2) I didn't take your comments as a complaint - I just used them as an excuse to share some of the thinking that went into the program.

Well, while I have your ear, let me put one more thing on my wish list. The power/duration curve is great, but all of the data points are from actual workouts and sometimes it doesn't make sense. For example, I don't think the line should ever go up as you move from left to right. But, there doesn't appear to be a smoothing option. That would be nice.

18-10.-2005, 12:22 AM

#18

acoggan

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by RapDaddyo

I'll pass your suggestion along to Hunter et al. (or you could just post it yourself at the forums at www.cyclingpeakssoftware.com). As for why you sometimes get such funny jumps, it's because the power-duration (or normalized power-duration) curve is, if I understand correctly, only drawn using selected time points. Otherwise, it's not possible to squeeze in all the data that needs to be displayed, due to lack of pixels.

18-10.-2005, 12:33 AM

#19

RapDaddyo

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by acoggan

Thanks. I'll post it myself. I would rather have you spending your time inventing things like NP rather than dealing with such trivial issues. While you're at it, how about a predictive sustainable power at a duration for which there are no data points, but based on the power/duration curve from actual rides. This would be useful for recreational cyclists to select a sustainable power for, say, a century.

18-10.-2005, 02:03 AM

#20

TMD

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Join Date: Oct 2005

Posts: 16

Re: Confused about setting Threshold Power

Quote:

Originally Posted by acoggan

First, I commend you on initially taking a "watch and learn" approach - that's basically what I did for the first couple of years that I used a powermeter, and it was only subsequent to that that I attempted to formulate/formalize a more structured approach to using a powermeter.

As for your question, I would say that your functional threshold power is probably around 275 W. It might actually be higher than that, depending on just how hard you actually pushed yourself during that particular workout. OTOH, it could also be slightly (~5%) lower, as the algorithm isn't perfect. For now, though, I'd suggest entering that value (unless you've got some reason to doubt it, e.g., the frequency distribution of your power shows a distinct "shoulder" at a significantly lower power). Over time, you'll probably be able to refine that estimate even w/o doing any formal testing, and should you decide that 275 W is too high, you can always retroactively assign a lower value. (CyclingPeaks actually recalculates your normalized power, IF, and TSS each and every time you open a workout, i.e., the values are not stored as part of the .wko file.)

One last comment: there are at least seven different ways of identifying your functional threshold power, eight if you want to calculate it assuming that it is a fixed fraction of your MAP. You can search the wattage list for a post titled "seven deadly sins" for more info.

Thanks for your response Andrew, and kudos for a terrific software package. Based on yours and Rapdaddyo's response I'll use normalized power - so that clears up my main question. I'm still confused, however, on the NP number from the Mean Maximal Power Graph on the athlete home page vs the NP number listed in the ride summary stats at the bottom of each indivdual ride. For example, I looked at the Mean Maximal NP graph and observed 274 watts for a 60min period that had a ride date attached to it. When, I went to the specific ride that was referenced and scrolled down to the hard number stats for 60min the watts were 271. I realize these two numbers are very close and certainly close enough for me, but I'm still a bit confused.

As with anything, the more experience I get with the Powertap and the more riding an testing I do, I'll gain a better understanding of what my TP is. Since, I am in my "watch and learn" phase, I'm not really too concerned what the initial value is since I'm really looking at the TP that I input as more of a placeholder (but at least one that is based on an educated guess).

18-10.-2005, 02:07 AM

#21

RapDaddyo

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by TMD

I looked at the Mean Maximal NP graph and observed 274 watts for a 60min period that had a ride date attached to it. When, I went to the specific ride that was referenced and scrolled down to the hard number stats for 60min the watts were 271.

The 271 is AP. Select it to highlight it (the little box to the far left of that row in the summary stats), then use your mouse to select the range on the graph itself. Then, you'll get the NP for that segment. I realize it sounds complicated and unnecessary, but that's how you have to do it in the current version of CP. Now, you may still not get exactly 274. To find the 274, you would have to export the workout file to Excel and do a rolling 60min NP calculation and find the largest value. I know, it's a pain but that's the only option that I know of.

18-10.-2005, 02:12 AM

#22

TMD

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Join Date: Oct 2005

Posts: 16

Re: Confused about setting Threshold Power

Quote:

Originally Posted by RapDaddyo

Actually, the AP for the segment was 220w and the NP was 271w - this data is not from the graph, but from the Summary Stats at the bottom of the page where you can view Kj, Heart Rate data, etc. for different time periods. When I get hpome tonight I can post more detailed info.

18-10.-2005, 02:17 AM

#23

frenchyge

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by TMD

Select the range titled Max 60 minute power (or something similar) by clicking on it, and the summary stats you mention will change to reflect just what is within that 60-minute range. If you don't have any particular range selected, then the summary stats will represent the entire ride.

18-10.-2005, 02:22 AM

#24

RapDaddyo

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by TMD

Then, that is for the entire ride duration. Above that section is a set of ranges (from 5sec to 60min). In all likelihood, your max 60min NP was higher than 271w. But, your max 60min NP is not necessarily on the ride of your max NP for the entire duration of the ride. I know this gets confusing, but the place to start is with the Mean Maximal NP chart. I think that's the chart that showed 274w you mentioned. That ride has your max 60min NP, but as discussed above it's not all that easy to find that precise 60 min ride segment without exporting the workout file to Excel and calculating a rolling 60min NP for the entire ride. The best way to get in the ballpark without exporting the file is the procedure I suggested.

18-10.-2005, 02:23 AM	#25
acoggan Registered User Join Date: Jul 2003 Posts: 2,622	Re: Confused about setting Threshold Power This might explain things best: CyclingPeaks actually started out as just an Excel macro, that would search through a .csv file to find your best ("peak") 5 s, etc., power. That aspect was retained as the macro grew into a program in its own right, with things like normalized power gradually brought into the mix. To date, however, the program doesn't search for your peak normalized power at any duration when analyzing/displaying individual files, only when creating a summary mean maximal normalized power chart on your Home Page. So, when you call up the file from the data on which your peak 60 min normalized power actually occurred, there's no direct way of finding it using CyclingPeaks...you have to export the data to e.g., Excel and do the calculations manually, as described by RapDaddyo. Again, another feature that hopefully will eventually be added...

18-10.-2005, 02:26 AM

#26

RapDaddyo

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by frenchyge

Actually, this isn't exactly correct. Selecting the range by clicking the box to the far left of the Peak 60min row (or any other row) will highlight the range in black but will not change the summary stats (including NP). You have to then select the range with your mouse (dark blue color), after which the summary stats reflect the selected range.

18-10.-2005, 03:22 AM

#27

frenchyge

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by RapDaddyo

Nahhh.... If you left-click on the white (maybe gray-ish), rectangular box that says "Peak 60min" in it, then the range will be selected and stats displayed. Clicking the far left column (to get the eye) does show the range, but that's not what I'm saying.

18-10.-2005, 03:33 AM

#28

RapDaddyo

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by frenchyge

Correct. I forgot about the feature you're talking about. I usually just use the Peak xx range to direct my attention to a range of interest. It is rare that I do any further analysis of the precise range, so I usually expand or shrink the selected range somewhat. For example, it's entirely possible that the Peak 60min segment has a few minutes of very low power at one end or the other, which is not the part of the ride I'm interested in. So, I use the box to the far left to zero in on a range and then select what I am specifically interested in with the mouse. I haven't used the feature you're talking about in so long that I forgot it existed. Anyway, neither procedure is going to get you to the Peak 60min NP. There is no automatic feature to find it. For that, you need to do more analysis.

18-10.-2005, 04:02 AM

#29

frenchyge

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by RapDaddyo

Anyway, neither procedure is going to get you to the Peak 60min NP. There is no automatic feature to find it. For that, you need to do more analysis.

When you select the Peak 60min range, and the stats show up in the summary below, the NP for that range appears there. While it's possible that the Peak 60min range does not also possess the highest 60min NP for the workout, I believe the 60min Peak AP and 60min Peak NP ranges will usually coincide.

18-10.-2005, 04:41 AM

#30

RapDaddyo

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Location: Las Vegas, NV

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Re: Confused about setting Threshold Power

Quote:

Originally Posted by frenchyge

Yes, you get the NP stat, but it's not true that the peak 60min AP is the same range as the peak 60min NP. I have differences up to 5w in my workout files as recently as the last 28 days.

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