General Discussion Triathlon Talk » Avg power vs. Normalized Power Rss Feed  
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2012-06-18 7:51 AM

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Subject: Avg power vs. Normalized Power
I was just curious how you use these metrics for training and racing.  I know athletes like Jordan Rapp has Normalized power as one of his metrics that he follows during races.  I guess what I'm asking is what is the difference, and how do you use them for your training and racing?  Thanks.


2012-06-18 8:13 AM
in reply to: #4266502

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Subject: RE: Avg power vs. Normalized Power

A simple explanation is that average power is just that, you actual power you averaged for a duration of time. Normalized power is "what your average power actually feels like to your body"

so if Avg Pw is 200w and NP is 215w then you averaged 200w, but the toll it took on your body is equivalent to 215w if you had ridden that 215w at a completely steady rate ie with a VI of 1.0

2012-06-18 8:35 AM
in reply to: #4266502

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Subject: RE: Avg power vs. Normalized Power

AP & NP can give you a very good idea of what you've done during a ride without even looking at all your splits.  If you rode a hilly course with an AP of 200, but an NP of 230, that immediately tells you that you were likely pushing the uphills quite hard and/or coasting the downhills.  So two things to look for when you dig deeper into the data.  1)  Were you crushing the uphills and burning your matches, or 2)  Were you keeping power at a pretty good level uphill, but easing way off on the downhills.  Either way, you can find areas where you could push, or take it easier.

Since my head unit doesn't give me NP I cancelled the zeros in my average power so the data is closer to NP, and I get a better/clearer idea of how hard I'm really working.  I manually create a new lap every 10min during a ride and aim for a specific wattage target on each lap.  The only time I'm really looking at current power is when I climb and I'm watching my effort level closely, the rest of the time I'm paying attention to avg power (I can only see one or the other).

I've trying to pay attention to keeping my VI (difference between NP & AP) pretty close to each other, and last week rode a 58mile ride with 3500 feet of climbing and kept VI to 1.03.  Come race day I hope to do the same so that coming off the bike I'll have hit my target - as opposed to having dug much deeper than originally intended.

For a Sprint/Olympic distance race I would allow a higher VI or NP as you're going to be more aggressive on hills, and you can afford to dip into the well a bit more.

2012-06-18 11:44 AM
in reply to: #4266502

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Subject: RE: Avg power vs. Normalized Power
Thanks so much for the replies.  This is really helpful.  I was wondering if taking out the zeros would be close to NP.  My focus this year is mainly sprints and olys and I have been pushing the uphills quite a bit.  I'm also trying to see how hard I can push and still have a decent 5k/10k run.  This information is very helpful.  
2012-06-18 12:30 PM
in reply to: #4266502

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Subject: RE: Avg power vs. Normalized Power
From my experience, dropping the zeros was closer to NP than AP was, though it still wasn't necessarily that accurate. Think of it more as how hard you're working when you're working. The one that's "best" to use is the one that you understand most and that fits in with how you think. For me, I had to tone the higher level bits down, so NP works well. And before that was available the no-zeros was more useful towards this end. But the next person could just as easily be better off with AP.
2012-06-18 12:37 PM
in reply to: #4267056

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Subject: RE: Avg power vs. Normalized Power

I went from doing most HIMs last year to Olys this year. I think the  advice to keep the NP and AP as close as possible is more for the longer races. I was told a high VI (NP/AP) was fine in the 'shorter' races. Not sure what the more experienced people would say.

I did a very hilly Oly two weekends ago and I ended up with a VI of 1.09. It would have been impossible to get a much lower VI unless I would have backed off on the hills and would have left gas in the tank. The downhills were so fast I was generating 0 power at 75km/h.

My NP was 90% of FTP and I ran fine. But my AP was only 83% of FTP.

I was happy to have the new firmware on the Edge500. I will continue to use NP and try to keep my VI low only on the long distances.



Edited by marcag 2012-06-18 12:39 PM


2012-06-18 12:45 PM
in reply to: #4267212

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Subject: RE: Avg power vs. Normalized Power

Well, you do want to keep your VI down, but that doesn't mean it has to be 1.00 for the very reasons you just listed. Making the best time with the available power is the goal, not the flattest output. Short course can likely absorb some spikes better than long course, but something really spiky is still going to hurt your legs come the run.

Now in draft legal, they'll pretty much throw VI out the window as they're trying to break each other in the bike and make breakaways. Matt Chrobot's recent power file examples between legal & non-legal really showed the differences.

2012-06-18 12:52 PM
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Subject: RE: Avg power vs. Normalized Power
I noticed that on the tri bike when the course is flat, like in the sprint races and TT's I've done so far this year, average power and normalized power are almost identical. When I'm out on the road bike either in group rides there is a large difference, which makes sense. There's a lot of 'who can get up the hill faster' followed by regrouping on the other side. It is not a steady effort.
2012-06-18 1:47 PM
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Subject: RE: Avg power vs. Normalized Power

For me, I think that average power is a better metric to use while riding. I only recently updated my 500 with the latest firmware, so maybe at some point I'll look at NP during a ride, but at this point I feel it's helpful to look at afterwards. As others have said, the more hilly the course, the greater variance between avg power and NP.

I did a ride on Saturday where my avg power was 285 and my NP was 288. I was actually pretty surprised that there wasn't a larger discrepancy. One thing that may help me keep NP and avg power (is it called AP?) closer is to virtually never freewheel. Even when descending at 35+ mph I try to keep up some power. The only real time I freewheel is when I'm coming to an intersection or when I run out of gears.

2012-06-18 1:57 PM
in reply to: #4267408

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Subject: RE: Avg power vs. Normalized Power
natethomas2000 - 2012-06-18 11:47 AM

For me, I think that average power is a better metric to use while riding. I only recently updated my 500 with the latest firmware, so maybe at some point I'll look at NP during a ride, but at this point I feel it's helpful to look at afterwards. As others have said, the more hilly the course, the greater variance between avg power and NP.

I did a ride on Saturday where my avg power was 285 and my NP was 288. I was actually pretty surprised that there wasn't a larger discrepancy. One thing that may help me keep NP and avg power (is it called AP?) closer is to virtually never freewheel. Even when descending at 35+ mph I try to keep up some power. The only real time I freewheel is when I'm coming to an intersection or when I run out of gears.

I agree on flat-ish courses.  But with enough downhill (or downhill + tailwind), coasting isn't necessarily a bad thing.  Especially on long-course.  You get less returns on the power that you're putting into it.  I'm not saying to go into the red zone on climbs, though.  But conservation is the name of the game as the distance goes up.

Take my opinion with a grain of salt... Nate still dusts my time on the bike

2012-06-18 2:01 PM
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Subject: RE: Avg power vs. Normalized Power

Nate, just for hoots, after this weekend publish your NP/AP for the segment on chemin duplessis, the last segment 20km of the IM MT course. I'm betting your NP will be a lot higher than AP

You won't be coming down at 36, you will be coming down at 46.

Not sure what gearing you will be using or your weight, but you will be pushing well above 300-350 on the way up and 0 on the way down. Hard to keep AP=NP. I was riding a 34/50 in front, a 11/28 in back and 19 times I hit 400w. I weighed 170lbs at that race.



2012-06-18 2:59 PM
in reply to: #4267448

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Subject: RE: Avg power vs. Normalized Power

I have a century ride from not too long ago that has a number of decent hills (~8,350 ft of climbing). AP was 250 and NP was 276. I needed that 28 and was still going down into the 50's in places. In the tris so far this year, the difference is much closer because I'm doing a more balanced effort. The last one was 327 & 332 with some rather small rollers that fed well into each other.

Where VI "should" be really depends on the course and the ability of the rider. Mine is likely to be flatter than some on a sort of hilly course because I can keep up on the downhills with the 54/42 up front and either the 11/23 or 11/28 on the back, depending on how bad the hills get. I can do alright spinning up more than some too. I find that the coasting downhills seem to cause more separation than the uphills, short of getting into power levels you might find in a crit attack. The coasting downhills tend to last a bit longer than a 400w effort. Someone with a lower FTP isn't going to hold a 400w effort for long. For Nate or myself, that 400w isn't as far above our average, so it won't be as big of a spike. I'll attack the rather small local hills, but have no need to coast down the other side as speeds generally don't reach 40, so there is only a few watts difference.

2012-06-18 3:42 PM
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Subject: RE: Avg power vs. Normalized Power
I agree with what some of the others have posted above - AP=NP is not always the best, or even possible outcome, of certain sections of a ride.  That said, overall a lower VI is going to mean you have not over cooked it on the bike and have been balanced throughout. 
2012-06-18 4:33 PM
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Subject: RE: Avg power vs. Normalized Power
marcag - 2012-06-18 3:01 PM

Nate, just for hoots, after this weekend publish your NP/AP for the segment on chemin duplessis, the last segment 20km of the IM MT course. I'm betting your NP will be a lot higher than AP

You won't be coming down at 36, you will be coming down at 46.

Not sure what gearing you will be using or your weight, but you will be pushing well above 300-350 on the way up and 0 on the way down. Hard to keep AP=NP. I was riding a 34/50 in front, a 11/28 in back and 19 times I hit 400w. I weighed 170lbs at that race.

Marc,

I bet you're right about that section! My goal wattage for the race is 285, my race weight will be around 162 and my gearing is 53/39 with a 11/25 out back. I usually roll with an 11/23, and this is the first time I'm going with slightly more gears. Hopefully it'll help a bit on that steeper section.

As for comparing NP vs AP, I ride with 4-mile autolap, so I can definitely share the splits and power post race.

2012-06-18 4:40 PM
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Subject: RE: Avg power vs. Normalized Power
Neil and Nate,  I am curious as to why you auto lap at regular intervals.  Is this because you are mainly looking at Average power and by auto lapping you will get a better understanding of what you're doing in small increments?  Or is there something else?
2012-06-18 4:53 PM
in reply to: #4267893

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Subject: RE: Avg power vs. Normalized Power
It's so you have a larger period than instant (or 3s etc), but small enough to spot a trend. Are you doing more or less than earlier in the race? With one long section, it's more difficult to see that as it takes a greater deviation to affect the average (of any type).


2012-06-18 5:34 PM
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Subject: RE: Avg power vs. Normalized Power

Mine is likely to be flatter than some on a sort of hilly course because I can keep up on the downhills with the 54/42 up front and either the 11/23 or 11/28 on the back, depending on how bad the hills get.

Not to derail this thread too much... but wouldn't you be better suited to a 53/39?  Or are you focusing on shorter events / time trials?  It's not really the 54 that's a big deal, but the jump from 39 to 42 has an adverse effect on steep hills.

2012-06-18 5:57 PM
in reply to: #4267973

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Subject: RE: Avg power vs. Normalized Power
spudone - 2012-06-18 6:34 PM

Mine is likely to be flatter than some on a sort of hilly course because I can keep up on the downhills with the 54/42 up front and either the 11/23 or 11/28 on the back, depending on how bad the hills get.

Not to derail this thread too much... but wouldn't you be better suited to a 53/39?  Or are you focusing on shorter events / time trials?  It's not really the 54 that's a big deal, but the jump from 39 to 42 has an adverse effect on steep hills.

As long as it doesn't get pulled....

2012-06-18 8:11 PM
in reply to: #4267919

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Subject: RE: Avg power vs. Normalized Power

brigby1 - 2012-06-18 5:53 PM It's so you have a larger period than instant (or 3s etc), but small enough to spot a trend. Are you doing more or less than earlier in the race? With one long section, it's more difficult to see that as it takes a greater deviation to affect the average (of any type).

^^^^^This^^^^

Since I can't autolap I manually lap every 10min which is going to be just over/under 5km depending on the terrain.  So whether I'm in a hilly or a flat section I know what my effort level is at NOW.  What I did an hour or even 30min ago doesn't matter so much.  I'll have a total target for the overall ride, and will break that down into sections (just mentally, nothing complicated), and each 10min I'll aim to hit the target.  If it's a couple of watts above/below, no big deal - big swings and I know I need to be more attentive and focused.

2012-06-19 7:26 AM
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Subject: RE: Avg power vs. Normalized Power
brigby1 - 2012-06-18 2:45 PM

Well, you do want to keep your VI down, but that doesn't mean it has to be 1.00 for the very reasons you just listed. Making the best time with the available power is the goal, not the flattest output. Short course can likely absorb some spikes better than long course, but something really spiky is still going to hurt your legs come the run.


I think this is a great post regarding pacing in triathlon:

http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=38195...

If you are interested you can check out a couple of articles by Dr. Skiba regarding threshold and time above threshold in endurance cycling.

Shane
2012-06-19 7:54 AM
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Subject: RE: Avg power vs. Normalized Power

gsmacleod - 2012-06-19 8:26 AM
brigby1 - 2012-06-18 2:45 PM Well, you do want to keep your VI down, but that doesn't mean it has to be 1.00 for the very reasons you just listed. Making the best time with the available power is the goal, not the flattest output. Short course can likely absorb some spikes better than long course, but something really spiky is still going to hurt your legs come the run.
I think this is a great post regarding pacing in triathlon: http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=38195... If you are interested you can check out a couple of articles by Dr. Skiba regarding threshold and time above threshold in endurance cycling. Shane

Shane,  Thanks for this post.  There is some great information right there.  



2012-06-19 8:13 AM
in reply to: #4268681

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Subject: RE: Avg power vs. Normalized Power

gsmacleod - 2012-06-19 7:26 AM
brigby1 - 2012-06-18 2:45 PM Well, you do want to keep your VI down, but that doesn't mean it has to be 1.00 for the very reasons you just listed. Making the best time with the available power is the goal, not the flattest output. Short course can likely absorb some spikes better than long course, but something really spiky is still going to hurt your legs come the run.
I think this is a great post regarding pacing in triathlon: http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=38195... If you are interested you can check out a couple of articles by Dr. Skiba regarding threshold and time above threshold in endurance cycling. Shane

Very nice! Will definitely look for more of his articles. The books were very good reading.

2012-06-19 8:30 AM
in reply to: #4267973

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Subject: RE: Avg power vs. Normalized Power
spudone - 2012-06-18 5:34 PM

Mine is likely to be flatter than some on a sort of hilly course because I can keep up on the downhills with the 54/42 up front and either the 11/23 or 11/28 on the back, depending on how bad the hills get.

Not to derail this thread too much... but wouldn't you be better suited to a 53/39?  Or are you focusing on shorter events / time trials?  It's not really the 54 that's a big deal, but the jump from 39 to 42 has an adverse effect on steep hills.

Largely, it was to lessen the gap between the rings some. I liked having roughly a 2 gear drop instead of 3 when going between the chainrings. For a while before doing the switch, I paid attention to how I was doing on what hills there are in the area and was plenty strong to make the jump. I can keep it above 70 with the 11/23 on anything in the area except for a brief spot on one hill (it's not hilly around here). The 11/28 has been enough to get me up and over things on the trips up into Wisconsin (as in driving a few hours up). Like the century ride I referenced above, that was much harder than a course like Quassy. I didn't need the 28 for that and was able to keep things in the 70's at least (I think, several gadgets died or had trouble).

It's not something I recommend to others as the 53/39 is probably the better option. Seemed a good solution for me, and is very specific to me. We just don't have hills that are 8 miles at 8+%. If I was out West, that might change though.

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