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NGP Normalized Graded Pace

NGP Normalized Graded Pace

Postby dbrillha » Fri Aug 23, 2013 10:30 am

Is there a calculation for NGP? I know this is a "secret" formula by Training Peaks, but I'd like to try to calculate my rTSS, which requires this.
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Re: NGP Normalized Graded Pace

Postby dbrillha » Sun Aug 25, 2013 8:29 pm

Okay... I've reverse engineered the NGP formula from WKO+ v3. I've created a whole bunch of different test workouts via SportTracks, exported the TCX files, uploaded into WKO+, and fit a curve to the resulting NGP and rTSS.

The results lead me to believe NGP is immature and unreliable.

First off, if you run a FLAT route, or you run a hilly route, in which you end where you started (gain = loss), the NGP (normalized graded pace) is the same as the actual pace. In other words, there is no compensation for all the hill work. Stephen assumes the effort to run up a hill is exactly the same as the gain running down hill.

Second, there is no influence from altitude, body weight, temp, wind, terrain (road -vs- trails), etc. It is well known that VO2Max drops by about 2% for every 300m above sealevel, which means pace X is more intense (closer to your threshold) the higher you go.

However, if you end up higher or lower than you started, here is the equation used by WKO+ to calculate NGP (where AP = actual pace).

NGP = AP / (1 + 4.8 * Grade)

For example, running up a 7% grade at a 10:00 pace. Your NGP = 10:00 / (1 + 4.8 * 0.07) = 7:29 (this is your equiv pace if you were running on a flat road)

Furthermore, if your FTp is 7:45 (the best pace you can run a 15K), and you ran up that 7% hill for 30 mins, the WKO+ v3 formula for rTSS is:

rTSS = 100.5 * 0.5^1.025 * (7:45/7:29)^2 = 58.2

============

Hope this comes in handy for some of you. But, I think the fatal flaw in rTSS is that you don't get any credit for running a loop or out-and-back hilly route. If climbs were given more points than descents, then a hilly course would result in a NGP that is faster than a flat course.
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Re: NGP Normalized Graded Pace

Postby gerhard » Mon Aug 26, 2013 3:50 pm

dbrillha wrote:First off, if you run a FLAT route, or you run a hilly route, in which you end where you started (gain = loss), the NGP (normalized graded pace) is the same as the actual pace. In other words, there is no compensation for all the hill work. Stephen assumes the effort to run up a hill is exactly the same as the gain running down hill.


Trails calculates some Grade adjusted pace algorithms:
http://code.google.com/p/trails/wiki/Fe ... usted_Pace

Most of those are based on studies, where they found that you loose more uphill than what you gain downhill.
Trails implements graphs, it seem reasonable to me. I am slightly better uphill than the default MervynDavies, and do not gain so much on steeper downhills. Overall I feel like hills are still not fully compensated.
Note: you need good elevation data (barometer) to make something out of the graphs...

GradeAdjusted pace is currently not included in the CF-Trails interface, could be added (most work is in CF).
Similar, the Ideal (Utopia) compensation factors from PerformancePredictor could be available from CF. I would assume the Ideal pace as in Trails is the interesting, it complex to add all extrapolation factors.
(If you have a reference for Elevation affecting performance, that could be added to PP...)
NGP formula in Trails would inflate the numbers if calculated for every point, still, could be added.
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Re: NGP Normalized Graded Pace

Postby dbrillha » Tue Aug 27, 2013 11:09 am

I've performed a bunch of tests on hill climbs and descents for me. What I've found is that my:

NGP for climbs = AP / (1 + 6.0 * Grade)
NGP for descents = AP / (1 - 2.5 * Grade)

For example, consider a 10 mile loop with 1400 feet of elevation change.

If I run up a 3 mile hill with a 4.4% grade, at a 10:30 pace, my NGP 8:18.
If I run down a 2 mile hill with a 6.6% grade, at a 7:50 pace, my NGP is 9:23.
And 5 miles is flat, so my 9:15 actual is the same as my NGP.

The overall average NGP is 9:00. That means I get some credit for running hills, rather than all 10 miles being flat. About 20 sec/mile more of an effort.

=====

What I find interesting is that if I didn't know the segment stats, and only knew the bare minimum about this run. That it was 10 miles long, that the overall average pace was 9:20, and that there was 700 feet of gain. I could come up with the SAME NGP. I don't need to evaluate the run as a whole bunch of segments.

NGP-dcb.GIF
NGP-dcb.GIF (31.68 KiB) Viewed 5461 times


I get that everyone will be different. But the general ratio of 6 -vs- 2.5 for climbs and descents, is probably relatively close for many of you. And the NGP -vs- Actual Pace differential for my climbs and descents feels right using these parameters.
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Re: NGP Normalized Graded Pace

Postby dbrillha » Tue Aug 27, 2013 11:14 am

References re: altitude changes to VO2Max (and therefore, the relative intensity of running at a fixed pace):

http://www.rice.edu/~jenky/sports/altitude.html

The body's adaptation to high altitude helps significantly but doesn't fully compensate for the lack of oxygen. There is a drop in VO2 max of 2% for every 300 m elevation above 1500 m even after allowing for full acclimatization.


http://www.ncbi.nlm.nih.gov/pubmed/16311764

VO(2max) would be decreased at altitude even when exercising at the same absolute maximal exercise intensity as at sea level and; (2) the decline in .VO(2max) in endurance-trained athletes (ETA) would be linear across the range from sea level through moderate altitudes.
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