Same Distance, Different Terrain, Different w/kg

[bradley7983]

Hello Forum - I'm just hoping to understanding something. This is probably a newbie question: For the life of me, I cannot seem to sustain the same power output on a flat course as I can on hills. I did a fitness test on a climb today, and I'm certain I can't produce the same numbers over the same flat distance. Is this typical for most cyclists?

[racerfern]

I can't produce the same consistent efforts on flats as I can on climbs. There are a couple of reasons:
1) Even though you're on the flats there are slight undulations where you suddenly have to really push as you go down a -.2% grade and subsequent increased effort to go up a .2% grade. At your limit, little things like this really stand out.
2) Wind doesn't affect you nearly as much on climbs (if at all) and the only real thing you need to overcome is gravity. On the flats wind can vary substantially, again at your limit these slight changes really stand out.

If you're doing intervals longer than 10 minutes you can look at the normalized power for the interval as that will give you a better indicator of your effort, smoothing out the peaks and valleys while giving a bit more credit for peak efforts. So on a flat you'll see a bigger disparity between normalized power and average power, while on a climb the two numbers should be very close to each other. What are the NP numbers for some of those efforts in your spreadsheet?

I do my fitness test on a climb thereby forcing me to try that much harder when I do intervals on flats.

[bradley7983]

Thanks, Fernando. I never thought about the minor changes (wind/elevation) on a flat, but now that you mention it, I do recall being sensitive to those variations. Good insight. Thank you.

Regarding NP, I haven't started tracking that yet, but it's always decently higher than my AP. I've gotten into the habit of looking at AP, so I'm admittedly hesitant to change my measuring method (AP vs. NP). Almost all of my riding is over rolling terrain, with cat 4 climbs mixed in. With that said, is best practice to use NP?

Thank you again!

[racerfern]

Assuming you don't have an iSport then continue as you are now. As long as you're hitting the lap button at the start and end of the intervals you'll be able to click on one of your laps and in the stats window see the AP and NP numbers. You can always create the "splits" later on in iB4 in case you miss one.

NP is always higher than AP since any "hard push" is weighted more than easier riding. Don't bother tracking NP for efforts less than 10 minutes, it gets skewed too easily. However for efforts of 30m or more NP is very useful. For long rides NP generally comes out to the same as AP if you excluded zeros, but that's another subject.

Comparing NP for dis-similar activities with the same perceived exertion should yield comparable numbers whereas AP might differ quite a bit more.

[NCH1]

You might also find some interesting information on NP, IF and TSS relevant to your training in the article linked below by Hunter Allen.
Alternatively, the Book Training and Racing with a Power Meter is a very good investment, whether you race or not. The book is available in the ibikestore.

Nik

http://home.trainingpeaks.com/articles/ ... score.aspx

[fastgreg]

Hi,

I have an idash and after a few rides outside I seem to be encountering the same thing - same exertion level but vastly different wattage between the flats and hills (maybe something is wrong with my setup?). On the tacx trainer throughout the winter I can hold 330w for 20 minutes and about 300w for a hour while climbing.

The other day on a flat one hour ride with relatively light winds I averaged 136 watts and was pushing quite hard. Occasionally with a slight headwind I looked down and I was averaging 150 watts doing 29k.

Does anything look amiss with the data below (I can provide the full file if you need it)?
Dist: 28.9 km (1:00:32)
Energy: 494.5 kJ
Cals Burn: 472.8 kcal
Climbing: 33 m
Braking: -5.6 kJ (-1.1%)
Min Avg Max
Power 0 136.2 399 W
Aero 0 94.7 179 W
Rolling 0 33.3 46 W
Gravity -192 4.3 219 W
Speed 0.0 28.6 39.8 km/h
Wind 0.0 26.2 36.5 km/h
Elev 16 28 49 m
Slope -8.0 0.07 7.9 %
Caden 0 77.0 101 rpm
NP 154 W; IF 0.821; TSS 68.1
CdA: 0.343 m^2; Crr: 0.0056
77 kg; 09/04/2011 1:48 PM
20 degC; 1010 mbar

I also went out to do some climbing the other day and here is a section of that file where I was climbing a few hills -
Dist: 2.1 km (0:06:26)
Energy: 118.5 kJ
Cals Burn: 113.3 kcal
Climbing: 103 m
Braking: -0.1 kJ (-0.1%)
Min Avg Max
Power 0 307.1 499 W
Aero 0 40.6 136 W
Rolling 12 23.0 31 W
Gravity -37 204.3 420 W
Speed 10.0 19.8 26.6 km/h
Wind 12.1 20.7 34.0 km/h
Elev 53 100 157 m
Slope -0.7 4.95 13.4 %
Caden 4 81.1 117 rpm
NP 321 W; IF 1.064; TSS 12.1
CdA: 0.343 m^2; Crr: 0.0056
77 kg; 08/04/2011 12:29 PM
15 degC; 1010 mbar

Thanks,

Greg

[racerfern]

Greg,

Your numbers are in line with each other. ASSUMING your windscaling is correct I come up with 145w for the flatish ride and 320w for the climbing. There are soooo many variables, I would have to see the files.

Your numbers are a just a bit low based on a quick look but they're certainly possible and maybe even normal. If you did your FTP test with this profile then just continue riding.

[fastgreg]

Hi Fernando,

Thanks for having a look. I will get out this week and do a FTP test on a flat course, and then do one with a significant climb in it.

I was wondering about the windscaling, on an idash the only calibration I can do is the 'Zero Wind' correct (I did do a calibration ride)? I have noticed that when I am not moving (and there is no wind) the wind setting reads -7 or 8 kph, is this correct? From reading some other post I understand that pushing 20mph or 32kph with no wind and on a perfectly flat road should require 200 watts...

I guess if everything is working properly I really need to work on my flat TT! I weigh 145 (5'10") and pretty much just train for hill climb races.

Again, thanks for your help.

Greg

[racerfern]

FTP tests on climbs generally yield higher results. It's easier to concentrate on holding a wattage number than on the flats where nothing is really flat. The slightest rises and falls in the road make it difficult to hold wattage. I also have the issue of cars whizzing by on my flats run that makes it tough as the wind ebbs and rises. If you can do a fitness test on the flats, I find it easier to do it with the wind where you're not affected as much as headwinds that change.

Assuming your wind scaling is correct and you zero out the wind, you will see wind numbers fluctuating at a stop. Velocomp is aware of this and it doesn't affect your ride. Notice that as soon as you ride away, the numbers go to normal. You're seeing this only at a stop.

[Mark_H]

It's probably to do with the fact that on the flat you are fighting wind resistance; on hills you are fighting gravity. Higher cadence muscles on the flat; lower cadence muscles on the climb. Different physical requirements.

Most training books note that hill climbing will elicit higher power output than flats and that we actually have a hill climbing FTP that is independent from the general flat terrain FTP.