Calibration questions

[Avanti]

Hi everyone,

Have had the IBike GenIII Pro for a little over a week now, many trials and testing later yesterday I was finally ready to take it out for a go at some intervals. Not having owned a power meter before honestly I have no idea where my watts etc should be at. I'm 28yo, 189cms tall, 79 kg and my bike fully loaded up takes my total weight to 92kg. I race and have a very solid base. Questions bear with me I have a few:
I'm concerned about my calibration testing, I did the cal ride out and back along with 7 coast-downs on a quiet slightly uphill street with what you call a medium grade bitumen. Everything to be honest seemed to go really well, I've looked at a number of post's on the forum and feel like my results aren't all that crash hot. I didn't go for a really aero position in these coast downs as the majority of my training is spent on the hoods. Can I ask for some feedback on my results.



So with those results in mind I went out yesterday to do 4 X 5 Min LT intervals, I forgot about power to do this as I'm yet to do any formal testing to get my power zones set up. So I took off at my prescribed HR Values and maintained 165 - 176 throughout all 4 intervals.It was a good session not great but I was very excited to get home and check these results out. Averages were ok on HR and Avg Speed, had a little left in the tank but I was happy with this trial run. The power data is below. Things to note from my point of view:
- Big gaps where power was non-existant (I didn't stop pedalling as it was a long straight narrow road slightly undulating...However Disregard the 3rd interval as I ran out of road on this...amatuer mistake!)
- My average power sort of sits around 240 w per interval...To be honest I know it's difficult to measure against others but I was dissapointed with this number as I believe I'm capable of higher numbers.


Guess I'm just after clarification on what I may have done wrong, any response would be very appreciated.
Cheers.

[dbrouse]

The data is showing that you stopped peddling a couple dozen times. Somewhere a heard something about power meters not registering if cadence is less than 35 rpm (???) or something like that. So maybe you didn't stop pedaling but it looks like you dropped below the minimum rpm required to calculate power.

It makes sense because the power dips correspond to the ends of your "efforts"...in most cases when I finish an effort I coast for a few seconds then spin it out.

I don't know enough about the device/calibration to confirm this but can someone look at the Crr for this profile?

I'm showing numbers like these:
CdA: 0.407 m^2; Crr: 0.0059

while you're showing
CdA: 0.239 m^2; Crr: 0.0109

Delane

[Avanti]

Hi Delane,

Thanks for the input, during the intervals the third was the only mishap where I had to turn around and thus my rpm would of dropped below 35rpm. I checked Garmin Training Center just to make to sure nothing weird happened and everything was normal. A very steady cadence and HR, the power dropoffs were noticeable if I were going on a decline which I expected but on the flip side during this time I was really trying to drive it down hill.

Those setting you mentioned were the one's giving me concerns especially the CRR, I decided when doing the coasts downs to let the unit calibrate this value as I wanted a realistic value. From what I've read the value I got is worse then riding on gravel and coarse bitumen, whereas the actual test section I used was a nice moderate grade.

[Velocomp]

Please post your ibcd4m file. Your CdA looks low and your Crr looks high.

Is this a road bike?

[coachboyd]

I took a look at the ride file and have a few comments.

First of all, John was right. . your cda looked a little too low and your crr a little low. I have attached a new profile here where I have fixed that. Save this file, then in your iBike software go to profiles->edit profiles->import and select this file. Then hit "send to iBike" and you'll be good to go.

Another thing I noticed is that you could really use the "user" interval feature of the iBike. I can tell based on the heart rate where your intervals where in this ride, but your power seemed to be all over the place (of course you were doing these based on heart rate so that explains why). When you do a shorter interval based on heart rate what happens is at first your power is really high (to get your heart rate to the targeted number), then to keep your heart rate the same your watts will actually have to start decreasing. This means that your intervals aren't as beneficial as they could be.

With the user intervals, you can see average watts, current watts, and elapsed time for each separate interval. Based on your new profile, you should try this workout again and aim for a target of about 320 watts. For the first minute or two of the interval it may seem somewhat easy to hold this, but the last minute will be pretty difficult. Then you rest and do it again. . .and again. . etc.

To access user intervals, hold the right button for two seconds while you are NOT moving. You will see the words "fit train" appear and then a menu will pop up that you can scroll to the right or left. When you see "user" hit the center button. Now you will access the "user" intervals whenever you hold the right button for two seconds when you are at speed.

Entering the user interval mode will start your first interval. You move to the next interval by pressing the center button, and you can review any previous intervals by scrolling with the up and down arrows. When doing intervals, aim for keeping the current and average watts as close together for the entire interval, and the average should stay around the same for the entire interval (320 at minute 1, 320 at minute 4).

Load up this profile and then try a few interval workouts. By doing this you'll really be maximizing the potential of training with power and that's when you'll see your biggest improvements.

[dbrouse]

(Sorry for jacking this thread)

Boyd...if my coach gives me this workout:

(6) 15sec HARD/15sec EASY
(6) 30sec HARD/1minute EASY
EASY for 5 minutes
6 minutes of 20sec HARD/20sec EASY
EASY for 5 minutes
10 minutes watts 205-235

Should I be using the user intervals?

[R Mc]

I'm not Boyd, but I'd say no--

There's no way you'll get all the button-pushing right while you're cross-eyed.

Pre-program that sucker in ib4 and send it to the iBike.

Then you just do the workout on auto-pilot like . . .

[dbrouse]

Once I start I thought all I had to do was press the center button to go to the next interval. No?

[R Mc]

You could, but I start second-guessing and miscounting.

Programming the intervals takes a little time, but one you do it, you have the workout, AND once you're on the bike, it's one or two button-presses instead of a couple of dozen . . .

You will have to specify a wattage target for hard though: 120% of ftp, 130%???

[lo-daddy]

I totally agree w/ R MC. Program the intervals and send it to the ibike. Then do what the ibike says. Kind of like having the coach tell you what to do while your on the bike. Once you download your ride to your PC, you will be able to see power/speed/HR breakdowns for each interval.

[dbrouse]

Ok...makes sense. I think you can only have 20 intervals...and it looks like I needed 22 to complete this one the way my coach sent it...

Any ideas?

[Avanti]

Wow thankyou so much for all the replies, Coach Boyd your post makes perfect sense and I really appreciate the tweaks you made. I'll take the unit out tomorrow and see how it pans out.
Your point about using heart rate as the barometer really makes sense of course it stands to reason that I pushed hard early trying to get it up but in turn fatigued and also hit high heart rate etc thus the power reductions. Next lot of intervals I will use the interval mode as described, again thankyou so much everyone a big help. I'll let you all know how it all works out.

[Avanti]

Sorry one more question, I'm fairly happy that my profile will be pretty close to spot on now. I'm not using the power meter for direct comparisons to anyone so my question is even if your profile could be recording slightly lower or higher readings...Does it really matter? ie As long as it's consistent measurement and not giving irregular data its still relevant to what your doing yes?

[dbrouse]

Avanti,

I think you are 100% correct. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results.

Once calibrated and stabilized on the bike, the iBike units appear to be extremely precise.

Delane

[R Mc]

to dbrouse about the intervals:

You get 20 effort/recovery steps (at least), so this workout might fit. And I'm pretty sure that I've done a workout with more than 20 steps . . .

If it doesn't, I'd exclude the last tempo-ish level effort: that's pretty easy to track with the timer and a lap feature.

As an aside, I have a question about the user intervals generating lap markers: last night we did our first time trial of the year, and I tracked part of my warm-up and the time trial effort itself via user-intervals. (we had a 25-30mph south wind, which meant that for 3 miles of the course 17mph was around 330average watts . . .

FYI, I REALLY like pacing a time trial only by watts and time--in a case like last night where the conditions are ridiculous, pacing by speed would have blown me up, while pacing by wattage meant I was able to finish strong. And learning that I was averaging 39mph on the tailwind section was sweet too . . .)

Anyway, when I downloaded the file, the lap markers were screwed up. My explanation: I pressed the right button to end several user intervals (lots of standing around waiting and I didn't see the need to have the clock running for that)--will that mess up how the unit places lap markers?

[Velocomp]

You may be creating a lap marker every time you enter and exit Fit Train...

[R Mc]

That would make sense . . .

Here's a feature request, since this thread has been thoroughly high-jacked:

how difficult would it be to get a lap marker inserted at the beginning of the first interval in a programmed set?

Currently I mark a lap about 30 seconds before I start the interval set, then start the program--and this means that anywhere from 20 seconds to a minute of "non interval" effort gets included in that first interval. It's not at all difficult to insert a lap-marker in iBike4 after the fact, but if it would not be a difficult matter . . .

[Avanti]

Thanks for your help CoachBoyd, all is going fantastic with the new settings really appreciate your help.