Polar power sensor: some questions



paolotom

New Member
Aug 2, 2005
2
0
0
Hi to everyone!
I am a new poster from Italy; I am a 44 years old triathlete focused on long distance races.
I would like to share some data from my last race (IM Germany) compared to another competitor that had fairly the same result in the bike section (180km no drafting).
I have a Polar power sensor and the other competitor has SRMpro.
My split was 5h15' (including a stop penalty of 9' #!?; so it was roughly 5h06') and he 5h05'.
Overall normalized power: me 241w / he 219w
hour 1: me 250w / he 233w
hour 2: me 264w / he 216w
hour 3: me 234w / he 218w
hour 4: me 234w / he 218w
hour 5: me 224w / he 212w

I have 290w CP30 and the data are consistent with my RPE and training data.
I am 160lb and 5ft7'; he is 155lb and 5ft10'

The difference of 22w in our NP (10%) could be reasonably due to different aerodinamics or someone had found a basic difference in watts readings between Polar and SRM ?
I attach a photo on the bike (I hope it is usefull).

Paolo
 
paolotom said:
Hi to everyone!
I am a new poster from Italy; I am a 44 years old triathlete focused on long distance races.
I would like to share some data from my last race (IM Germany) compared to another competitor that had fairly the same result in the bike section (180km no drafting).
I have a Polar power sensor and the other competitor has SRMpro.
My split was 5h15' (including a stop penalty of 9' #!?; so it was roughly 5h06') and he 5h05'.
Overall normalized power: me 241w / he 219w
hour 1: me 250w / he 233w
hour 2: me 264w / he 216w
hour 3: me 234w / he 218w
hour 4: me 234w / he 218w
hour 5: me 224w / he 212w

I have 290w CP30 and the data are consistent with my RPE and training data.
I am 160lb and 5ft7'; he is 155lb and 5ft10'

The difference of 22w in our NP (10%) could be reasonably due to different aerodinamics or someone had found a basic difference in watts readings between Polar and SRM ?
I attach a photo on the bike (I hope it is usefull).

Paolo

Ciao,

Unless the SRM has been carefully calibrated (not from the factory) it may be difficult to know whether it is reading correctly, as SRMs have been known to come from the factory poorly calibrated (e.g., Gardner et al 2004).

Additionally, we also know that Polar's may not always be accurate and can be off up to ~ 10 % (see Millet et al, 2003).

Thus you are comparing (possibly) two unknowns which makes analysis between yourself and your friend difficult. additionally, as you are different mass and height this will also lead to different power scores, and if you have different equipment this again will be an issue.

The only real thing we can say, is that you started way too hard in the first two hours and faded badly. Of course, the first two hours could have been up a mountain (??) requiring that power, but in general more even pacing would be better in terms of managing fatigue, especially for the run afterwards

ric
 
ric_stern/RST said:
Ciao,

The only real thing we can say, is that you started way too hard in the first two hours and faded badly. Of course, the first two hours could have been up a mountain (??) requiring that power, but in general more even pacing would be better in terms of managing fatigue, especially for the run afterwards

ric
Ric, You are right!
I planned to stay in the 220/230w range but I take the penalty after only 25 minutes and I tried to fill the gap on my timetable and I have to be very carefull passing people (I had to be very fast) in order to avoid a second penalty (disqualified).
Anyway it was a big mistake: I filled the gap somewhere in the middle of the bike but the second part of the run was really, really challenging and I lose what I gained with the interests.
It was a rolling course so in the first 2 hours I didn't climb more than the rest of the race.

I know that there are too many variables that affect wattage results but your answer is clear: I have to consider a 10% error.

Cheers
Paolo