Are my Power Values unrealistically low??

[timbradley]

I have recently gotten myself a polar power output sensor kit to go with my S720i (I'm too poor for a powertap!).

Have been using it indoors on my trainer only since I bought it, and, other than once when the sensor got moved and I was putting out about 3kW(I wish!!!!!!!) the readings have seemed surprisingly low

Values as calculated on TrainingPeaks.com acordding to my rides:

CP.2: 417W
CP1: 230W
CP6: 191W
CP12: 163W
CP30: 146W
CP60: 122W
(Nothing Higher than this has been estimated)

Now, from looking at other peoples values, these look somewhat low...I have set the Power sensor as close as possible to the chain at 39x12, remembering that my non-trainer wheel has an 11-23 Cassette, so I have to be a wee bit generous with space.

I'm 27, I don't race, but I think I'm in pretty good shape, 6'1", 77kg, lean but not terribly skinny

Are these values a bit low?

 

[peterpen]

yes, those are pretty low. But take it out on a group ride or hard training ride and see if they stay that low - the trainer is not ideal for such things unless you're doing specific workouts/ testing. If you just sat on the trainer and spun while watching a DVD, your numbers might really be that low. If you take it outside and put in some hard efforts and your numbers stay that low, you're either untrained or the Polar is set up incorrectly.

 

[Tom Anhalt]

I have recently gotten myself a polar power output sensor kit to go with my S720i (I'm too poor for a powertap!).

Have been using it indoors on my trainer only since I bought it, and, other than once when the sensor got moved and I was putting out about 3kW(I wish!!!!!!!) the readings have seemed surprisingly low

Values as calculated on TrainingPeaks.com acordding to my rides:

CP.2: 417W
CP1: 230W
CP6: 191W
CP12: 163W
CP30: 146W
CP60: 122W
(Nothing Higher than this has been estimated)

Now, from looking at other peoples values, these look somewhat low...I have set the Power sensor as close as possible to the chain at 39x12, remembering that my non-trainer wheel has an 11-23 Cassette, so I have to be a wee bit generous with space.

I'm 27, I don't race, but I think I'm in pretty good shape, 6'1", 77kg, lean but not terribly skinny

Are these values a bit low?

First, you need to get the chain closer than that. If the chain isn't actually rubbing on the case in a 39-12 combo, it's not close enough...seriously.

The key measurement is that in your largest USEABLE combo of large chainring and larger cog make sure that the chain is never further than 30mm from the top of the case. If that makes it rub in some extreme small-small combos, so be it. You shouldn't be cross-chaining like that anyway.

Second, physically weigh the chain and verify that you've entered the correct chain weight and length into the head unit. Also, confirm your measurement for the chainstay length.

Lastly, I hate to say it, but the Polar is known for "hit or miss" performance on indoor trainers. I've actually gotten pretty consistent results in a test on a Computrainer and I know of at least one other person who reports the same. However, there's also a lot of evidence out there of flakey trainer operation, so I'd take whatever results you get off of a trainer with a HUGE grain of salt.

If you want to try to get a better handle on the accuracy, take it outside and find a hill to climb. Then, compare the results to what's predicted at analyticcyling.com...making sure, of course, to input reasonable numbers (i.e. don't just blindly use the default settings).

Hope this helps,
Tom

 

[RapDaddyo]

Which trainer do you use? Some on this forum (e.g., frenchyge) have some pretty good data on the power/speed relationship for their trainers (e.g., Kurt Kinetic Fluid). And, there's this comparison chart for many other trainers http://www.geocities.com/almost_fast/trainerpower/. Most trainers heat up during the course of an interval, which changes the speed/power relationship, but at least it will give you another data point for validation of your Polar numbers.

 

[gclark8]

After the recent TdF power hype, I did some readings on the training equipment at the gym, rowing and cycling.

I am over 55, 85kg and reasonably fit, my training is based on HR ranges with a Max HR 160.

HR 150 = 156 watts
HR 135 = 125 watts
HR 125 = 120 watts
HR 117 = 115 watts
HR 105 = 100 watts

I don't see your figures being too low.

 

[dm69]

After the recent TdF power hype, I did some readings on the training equipment at the gym, rowing and cycling.

I am over 55, 85kg and reasonably fit, my training is based on HR ranges with a Max HR 160.

HR 150 = 156 watts
HR 135 = 125 watts
HR 125 = 120 watts
HR 117 = 115 watts
HR 105 = 100 watts

I don't see your figures being too low.

lol, u think you can put out a comparable amount of power rowing compared to cycling? I think at my max hr i would put out about 20watts rowing

If they were your numbers cycling ^ then you probably need to ride more often

 

[Sillyoldtwit]

After the recent TdF power hype, I did some readings on the training equipment at the gym, rowing and cycling.

I am over 55, 85kg and reasonably fit, my training is based on HR ranges with a Max HR 160.

HR 150 = 156 watts
HR 135 = 125 watts
HR 125 = 120 watts
HR 117 = 115 watts
HR 105 = 100 watts

I don't see your figures being too low.

Sorry George but those figures are very low. I'm well into my 60s and have been training seriously since Feb and I could spin 156 watts all day. If you have a spare couple of days with plenty of time on your hands, take a read of my thread - It's killing me but...

One more thing, forget HRMs. When I do my 20minute plus intervals I cover up the HR indicator because I don't want it telling me to slow down. As RD once said, "your heart will take anything you throw at it" or words to that effect.

When I finish an interval, I take a peek at the HR and if I've worked hard it is around 165 and that's not the max because I'm nowhere near spewing up my breakfast. But everyone is different when it comes to HRs.

So depending on what your goal is, adjust your training accordingly. If you want to ride faster and climb better, then you have to do some serious workouts. If you like just cruising on the bike, then your figures are fine.
Enjoy cycling - it's a great sport! TYSON

 

[ZimboNC]

One way to very roughly corroborate the power data you're seeing would be to record your solo outdoor speed on a flat stretch of ground with little or no wind. If you can average 20mph for a 30 minute ride then I would say that your power measurements are flawed.

--Steve

 

[SaintAndrew]

One way to very roughly corroborate the power data you're seeing would be to record your solo outdoor speed on a flat stretch of ground with little or no wind. If you can average 20mph for a 30 minute ride then I would say that your power measurements are flawed.

--Steve

ballpark, how many watts would the average joe put out to be @ 20mph for a half hour?

 

[MY02_STi]

ballpark, how many watts would the average joe put out to be @ 20mph for a half hour?

85kg rider on (very) flat ground, say 170-180W. Anything less than (very) flat maybe up to around 240W

 

[RapDaddyo]

ballpark, how many watts would the average joe put out to be @ 20mph for a half hour?

I have a 3-mile circuit that I am planning to use for a century ride in less than 5 hours with my cycling club (primarily recreational riders). I chose the circuit because it is very flat (total of 38' of gross climbing per lap) and the road surfaces are wide and smooth. There are 4-90 degree right turns, which slows speed down a bit. Wind is never completely calm, but I have done some testing with light winds (~5-10mph). It takes just a little more than 200W to average 20mph on the course and I weighed ~82kg when I did the testing.

 

[ZimboNC]

Another data point: I weigh 162 pounds and did a closed-circuit solo century with about 40 feet of climbing per mile (4000 feet total). I was in the drops a little less than 1/2 of the time. Removing the stoplights from the data, I averaged 20.8 mph and averaged 230 watts.

So, the question is... based on the various wattage quotes you are getting, do you think your power meter readings are erroneous?

--Steve

 

[SaintAndrew]

85kg rider on (very) flat ground, say 170-180W. Anything less than (very) flat maybe up to around 240W

whatr if you weigh 100kg's lol? (i stopped riding and started lifting alot for a couple years)

 

[MY02_STi]

I have recently gotten myself a polar power output sensor kit to go with my S720i (I'm too poor for a powertap!).

Have been using it indoors on my trainer only since I bought it, and, other than once when the sensor got moved and I was putting out about 3kW(I wish!!!!!!!) the readings have seemed surprisingly low

Values as calculated on TrainingPeaks.com acordding to my rides:

CP.2: 417W
CP1: 230W
CP6: 191W
CP12: 163W
CP30: 146W
CP60: 122W
(Nothing Higher than this has been estimated)

Now, from looking at other peoples values, these look somewhat low...I have set the Power sensor as close as possible to the chain at 39x12, remembering that my non-trainer wheel has an 11-23 Cassette, so I have to be a wee bit generous with space.

I'm 27, I don't race, but I think I'm in pretty good shape, 6'1", 77kg, lean but not terribly skinny

Are these values a bit low?

Tim, I use the Polar unit on my trainer exclusively and it correlates very well with the data I get out on the road (although this does not happen all that often as the bike with the Polar unit fitted is a very old steel frame )

I find the polar unit almost useless for 'sprint' type efforts on the trainer as the unit seems to take around 20 seconds or so to stabilise and give 'normal' readings but for Steady State L4 and L5 efforts it seems to give very good results.

Now for the bad news: I'm 50, I do race, I'm 6' 1" (185.4 cm) and 79 kg (which is fairly similar to you - except for our ages )) and on a recent L4 2*20:00 session (this past week) my figures were:

CP5: 376W
CP10: 350W
CP20: 337W

Maybe the setup of your Polar unit is a bit off. As a simple check (which I've done and it works) is just remove the battery completely and re-install and then see if you're getting the same readings

Hope this helps

 

[timbradley]

Thanks for all the responses - I'll adjust the power unit with respect to the largest combo it will operate on w/o cross chaining (53-21) and report back with my results

Although not for a while as I damaged my shoulder on the weekend...off to the doctor tonight to try to find out what I did to it!!

Cheers all

 

[Tom Anhalt]

Thanks for all the responses - I'll adjust the power unit with respect to the largest combo it will operate on w/o cross chaining (53-21) and report back with my results

Although not for a while as I damaged my shoulder on the weekend...off to the doctor tonight to try to find out what I did to it!!

Cheers all

Good luck with the doctor!

When you get back to checking your PM out, don't forget to recheck your chain weight and chainstay length values

 

[timbradley]

Well, it may be a little while until I get the opportunity to test out the PM adjustments!

Apparently, I have capsulitis in my right shoulder - doctor was of the opinion that it will be a couple of months before I have full strength use of it again!!

This sucks!