Interval Training 2x20, User Mode

[Landim]

Friends, I am starting on the interval training routine(have been using the unit just for learning on the beginning).

So I went for a ride today to do 2x20 minutes interval, I stoped and started the user interval. The first interval, the ibike gave me an average of 280w, and for the second 251w(this I remember).

But tonight when I came to download the files to the computer I got:

Dist: 12,6 km (0:20:03)
Energy: 390,8 kJ
Cals Burn: 373,6 kcal
Climbing: 61 m
Braking: 0,0 kJ (0,0%)
Min Avg Max
Power 213 324,9 423 W
Aero 0 274,5 611 W
Rolling 29 42,6 58 W
Gravity -432 1,9 288 W
Speed 25,9 37,8 51,2 km/h
Wind 25,1 39,3 53,7 km/h
Elev 29 44 55 m
Slope -3,7 0,02 3,9 %
Caden 56 96,4 110 rpm
HR 142 179,9 186 bpm
NP 327 W; IF 1,310; TSS 57,3
CdA: 0,365 m^2; Crr: 0,0048
86 kg; 17/6/2010 06:23
25 degC; 1014 mbar

and:

Dist: 13,0 km (0:20:02)
Energy: 358,2 kJ
Cals Burn: 342,5 kcal
Climbing: 60 m
Braking: 0,0 kJ (0,0%)
Min Avg Max
Power 177 298,0 405 W
Aero 0 237,7 601 W
Rolling 33 43,8 59 W
Gravity -427 9,2 267 W
Speed 29,6 38,9 52,6 km/h
Wind 19,3 36,1 52,0 km/h
Elev 24 39 51 m
Slope -3,8 0,10 3,5 %
Caden 55 94,9 118 rpm
HR 120 173,5 184 bpm
NP 300 W; IF 1,201; TSS 48,1
CdA: 0,365 m^2; Crr: 0,0048
86 kg; 17/6/2010 07:00
26 degC; 1014 mbar

So, I am a little confused, don't know what to think. During the interval I tried to keep an steady power and I saw the number droping from 320w to 280w ap(first) and from 280 to 250w ap(second), it surely felt harder than 250w. Any ideas on what I am doing wrong?

Cheers,

Leandro

Ps. Sorry if I do not make my english very understandable(I am from Brazil).

[Russ]

Hello Landim,

I was hoping some of the more regulars would answer but I will take a few guesses.. Actually I am not sure EXACTLY what you are asking but.

First, when you download to the computer, the default has been to do an automatic analysis on your data and apply some corrections. This may explain the higher avg power recorded on the computer.
This may even be in line with your expectations from perceived exertion that you mentioned.

As to the changing values as you ride, if you had a notable increase in barometric pressure during your ride, for example, then the iBike would be correcting your overall climbing to a decreasing elevation perception, which would be corrected for in the route analysis, if you finished at the same elevation as you started. Beyond that, I do not know unless your iBike is moving progressively during your ride. Also possible you are a little over trained and can't hold up the watts???

Just throwing out a few possibilities.

Russ

[lorduintah]

Russ is probably leading you in the right direction. You can check your preferences and see if you auto analyze the route upon loading a file. You can choose to not run an automatic route analysis or revert to the original and then perform analyses step by step or auto-route after you have had a look see. You can also correct altitudes, if you know the start and ending altitudes or the start and end were at the same place.

When you run the auto-route, the screen also allows you to look at tilt corrections made to your data, which may influence your watts.

Not being able to exactly duplicate the watts on two intervals - you are not greatly off between the two and as Russ said a little over-trained, de-hydrated or many other residual factors could lower your output, but your body may still feel as if you are doing the same level of exertion.

Tom

[racerfern]

Just a quick comment:

I don't think you'll have sufficient barometric changes in a 20 minute period to produce changes like that. AND if you did, I doubt it would happen twice. I vote for being unable to hold the wattage goal (for reasons known only to you).

FWIW, I believe my raw iBike data first and foremost. As long as I've done a wind offset I think it's on the money and most importantly it's consistent. I'll get a slight tweaking once I download the data because of tilt correction but I choose to have none of the automatic adjustments and I specify my starting and ending elevations.

[rcmaps]

I'll get a slight tweaking once I download the data because of tilt correction but I choose to have none of the automatic adjustments and I specify my starting and ending elevations.

I do the same too most of the time. Racerfern, do you know why the tilt drifts downwards over the course of a ride just about everytime? (well at least for me recently) This would cause a slightly lower power reading on the unit during the ride.

[racerfern]

My tilt tends to drift upward slightly on almost every ride so the on unit display is ever so slightly higher (the opposite of your experience). I don't know why it consistently goes in one direction or the other. However, the unit seems to have less tilt error in one second recording. FWIW I never use one second recording unless I'm doing very short intervals or a fitness test.

[Landim]

Thank you for the tips.

I will turn off the auto analysis option. The drop in power was not the issue(second interval). Just the readings ON the bike and ON the software later.

Is there any tip on where I can find the real elevation I start my ride? Google Earth?

I will do those intervals again tomorrow, see what happens.

[racerfern]

I use Google Earth if I'm going to a remote location for the first time. For my rides from home I still switch to entering the known elevation even if the iBike gets it right.

Lastly, I don't have any of the other features checked such as out/back or drafting. I usually ride with the top window showing wind speed rather than actual speed so I see the fact that I'm drafting by the huge change in relative wind speed and the matching drop in watts to maintain speed.

If a user fails to do a proper tilt, wind offset or somehow screws up the settings then the Analyze Route feature is awesome. However if you're setup is good, Analyze Route confirms your numbers without any adjustments rather than change them, IMO.

[Landim]

Thanks Fernando, I just did what you said, and returned to the original download. Now it is showing exactly what I did during the ride. Feels better for the data, but worst for the poor avg watts, reality is a hard

Got an elevation of 29m on Google, ibike found 34. It changed very little on the avg an NP. Very good.

Another question, the data does not match the online calculator such as Kreuzeter and others. Any tips on that?

[racerfern]

I use, http://bikecalculator.com/veloUS.html as it gives results that I can rely on and allows factoring in the wind. I've lost quite a bit of weight over the last few years and this calculator has allowed me to tweak my profile to be more aero as I trim down.

I'll look at your ride when I get home as corporate doesn't allow iBike software.

[lo-daddy]

Fernando the bike calculator website is very cool. It also confirms that my power numbers have always seemed way too low to me. It's always amazed me when people talk about FTP of 250W and greater. I've done calibration rides, coast downs, worked with Coach Boyd, and have gotten help from technical support to try to get a good profile. It amazes me when people report that are able to have FTP of 250W and greater. I raced a sprint triathlon in Charleston this past weekend. The race is advertised as 12.8 miles. My ibike reported under miles. My average power reported by the ibike was 190.4 and NP was 199W. My average speed was 22.1 MPH. Out of more than 300 people I had a top 30 bike split. I say this not to brag, but to point out I wasn't just soft pedaling. According to the web site bike power calcuator web site my average power of 190 W should have resulted in an avg speed of around 13.3 mph. If you use the website to find power from speed, my avg. power should have been much higher than the reported 190W from the ibike. I'm 5'10", 172lbs, and my total bike weight is 195. I've attached my most recent cal ride, and the race profile. Hate to hijack the thread, but I would be interested in someone looking at my numbers compared to the bike calculator website. Thanks for any help that can be offered to get a useable profile.

[racerfern]

@ lo-daddy
A couple of questions and comments:

1) Was this an out/back?
2) Were you on a TT bike?
3) Have you considered switching to profile 2 and trying the EST Aero function?
4) I don't see how you could possibly have a almost a mile difference. Even if your wheel size is substantially larger it would only account for a little more distance. Whoever said 12.8 miles? Have you accurately measured out your wheel circumference with you on the bike?
5) .263 is crazy low for CdA. Again TT bike? But what tires> .0059 seems high.

6) Lastly, IF you were on a road bike I would expect a CdA of about .35x. That would give average wattage of about 232 for this ride.

You have a few things you need to look at including your wind scaling which is negative on your cal ride.

Bike calculator is not perfect, but it's really really good.

[rcmaps]

I use, http://bikecalculator.com/veloUS.html as it gives results that I can rely on and allows factoring in the wind. I've lost quite a bit of weight over the last few years and this calculator has allowed me to tweak my profile to be more aero as I trim down.

I'll look at your ride when I get home as corporate doesn't allow iBike software.

Thanks a lot for this tip racerfern !

Just checked this out tonight and compared a ride I did today with the website and for a 96 min ride, the average watt from my iAero compared to this was only 2 Watts lower! Probably due to rolling terrain but overall average grade was 0.1%. Temperature probably dropped a couple of degrees and it also started to rain about 15 mins into the ride affecting barometer.

Also calories was only out by 10 !!!

On another note, I got a Low Batt warning partway into the ride. I stopped, turned off the unit and restarted it and to my relief it didn't complain any further during the ride and when I got home, I did have two separate ride files logged! Phew! Must remember to carry spare batteries on future rides especially during the colder weather (48 F today).

Gives me great confidence that my many calibration and coast down rides I did last month is somewhat correct and that my iAero is properly dialed in.

Great tool to check and calibrate wind offsets in future (ie for times that I can't do a proper wind offset prior to rides!)

[Landim]

How do we work with the Trans. Efficiency?

[racerfern]

Trans Efficiency is Cm which in iBike software is set at 1.02. I take that to mean divide by 1.02. IOW, 98% efficiency. So you can change the Trans Efficiency to 98%.

[lo-daddy]

@ lo-daddy
A couple of questions and comments:

1) Was this an out/back?
2) Were you on a TT bike?
3) Have you considered switching to profile 2 and trying the EST Aero function?
4) I don't see how you could possibly have a almost a mile difference. Even if your wheel size is substantially larger it would only account for a little more distance. Whoever said 12.8 miles? Have you accurately measured out your wheel circumference with you on the bike?
5) .263 is crazy low for CdA. Again TT bike? But what tires> .0059 seems high.

6) Lastly, IF you were on a road bike I would expect a CdA of about .35x. That would give average wattage of about 232 for this ride.

You have a few things you need to look at including your wind scaling which is negative on your cal ride.

Bike calculator is not perfect, but it's really really good.

Fernando,
Thanks for the reply. The cal ride was an out & back, but the race profile was a loop. My wheels are 700 x 23C. I used the factory default setting of 2096mm for the tire circumference. From everything I've read on the forum it appears the fast start screen with the new versions is supposed to be prety accurate. When I first got the ibike (more than 6 months ago) I did several coast downs post calibration ride, but my wattage numbers seemed low. I was told by customer support to not worry with the coast down but to rely on the fast start screen for profile creation. Coach Boyd sent a profile and customer support have also helped with a profile. My ibike is set up on a TT bike. The ibike is on a handlebar mount, and I also have a remote wind sensor. I let the ibike sit outside ~ 5 min before riding to acclimate to the outside temps and I always do a wind calibration prior to riding. Prior to cal rides I do several wind cal.
The website listed the race as 12.8 miles, but I would not be surprised if the course was short. The profile from the cal ride was the profile that was used in the attached race file. I was wearing a tri suit w/ an aero helmet. I will measure my tire circumf. tonight and try another calibration ride. I feel like I've really given the ibike a chance but it's frustrating trying to get a reliable profile and at this point I don't trust any of the data from the ibike. Perhaps it would have been better to work out the quirks in the existing ibike product line before moving on to bigger and better dashy things.

[coachboyd]

Landim,
Here is what I think happened. You have a long out and back ride where something happened to your wind data. Either the wind picked up during the ride, or your wind offset drifted.

When you analyzed the ride automatically, it "corrected" the wind data for the out and back and assigned it a zero average for the ride. If the wind picked up while you rode, then this would not be the case (which is why when you hit analyze route it asks if the wind had changed). I think your original data, before the auto route feature kicked in, is the better data to use.

Lo-daddy
Do you have a picture of your setup and with you on the bike? From just glancing at it, if you are on a TT bike, then the data looks good. If you were on a road bike, then I think the cda is a bit too low. One trick you may want to try is to soft pedal or even backpedal while going down a slight hill in your normal position. If you see the watts hovering around zero then you are good to go.

[Landim]

Coach, that's exactly what happened. We have very strong and crazy winds down here in Fortaleza.

Thanks, I have been using the Analise route feature wrongly.

[lo-daddy]

Lo-daddy
Do you have a picture of your setup and with you on the bike? .

I attached 3 pictures. Hopefully I did that right.

[coachboyd]

I would leave your profile right where it is based on those pictures. You're in an aero position, but with the bars that wide, the cda will be higher (and you'll be more comfortable) than if you had a super narrow aggressive position.

I think that with that position your data looks just fine and now you can just worry about going out and riding hard!

[Landim]

I do not want to create a new thread, so I'll just ask here. Last tuesday a went for intervals, did a 2x20' 283/273np. Today I did a 1x20' at 320w and a 1x30' at 317w. I am uploading the files to some one check if there is something off the readings today. I felt pretty good today, but it is kind a weird to get this values.

Thanks for the help.

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