Shared access to a SRM power meter

goldsmith_robert

Im trying to assist some amateur riders with their training. They don't currently have access to a PM and are unlikly to fork out the cash to get one each. The local club has kindly offered to buy one if it would help people train more effectively. This would mean we could estimate FTP / MAP for them on a turbo throughout the season. But they would not have the PM on their bike for training.

What is the best way for them to estimate training intensities during training without a PM? Is it worth the outlay of £1000+ for the club to provide this?

I know HR is v.variable, is it better than the cyclists perceived level of exertion?

What about giving them a set speed (i.e. cover X miles in XX time) for each workout?

Are we better off putting the SRM PM on a 'test bike' (one that can be altered to approximate their road bike set up) and testing on a 1hr or 20min TT on the road / track? (rather than a turbo). At least this could give them speeds to train at (on the flat, in still conditions!).

Thanks in advance.

jibberjim

Why get an SRM, when for the same money you could get both a Shimano and Campy Powertap wheel that could be shared and used on their own bikes.

schweiz

jibberjim wrote:

Why get an SRM, when for the same money you could get both a Shimano and Campy Powertap wheel that could be shared and used on their own bikes.

+1

With a rear wheel you can swap easily between bikes. PT is ANT+ compatible so Garmin Edge 605/705/500 computers can also be used to show the power output too and that can be matched against a GPS route.

The accuracies of SRM and PowerTap are similar:

Gardner, A. S., Stephens, S., Martin, D. T., Lawton, E., Lee, H. and Jenkins, D. (2004) Accuracy of SRM and power tap power monitoring systems for bicycling. Medicine And Science In Sports And Exercise, 36 7: 1252-1258. wrote:

Although manufacturers of bicycle power monitoring devices SRM and Power Tap (PT) claim accuracy to within 2.5%, there are limited scientific data available in support. The purpose of this investigation was to assess the accuracy of SRM and PT under different conditions. Methods: First, 19 SRM were calibrated, raced for 11 months, and retested using a dynamic CALRIG (50-1000 W at 100 rpm). Second, using the same procedure, five PT were repeat tested on alternate days. Third, the most accurate SRM and PT were tested for the influence of cadence (60, 80, 100, 120 rpm), temperature (8 and 21degreesC) and time (1 h at similar to300 W) on accuracy. Finally, the same SRM and PT were downloaded and compared after random cadence and gear surges using the CALRIG and on a training ride. Results: The mean error scores for SRM and PT factory calibration over a range of 50-1000 W were 2.3 +/- 4.9% and -2.5 +/- 0.5%, respectively. A second set of trials provided stable results for 15 calibrated SRM after 11 months (-0.8 +/- 1.7%), and follow-up testing of all PT units confirmed these findings (-2.7 +/- 0.1%). Accuracy for SRM and PT was not largely influenced by time and cadence; however. power output readings were noticeably influenced by temperature (5.2% for SRM and 8.4% for PT). During field trials, SRM average and max power were 4.8% and 7.3% lower, respectively, compared with PT. Conclusions: When operated according to manufacturers instructions, both SRM and PT offer the coach, athlete, and sport scientist the ability to accurately monitor power output in the lab and the field. Calibration procedures matching performance tests (duration, power, cadence, and temperature) are, however, advised as the error associated with each unit may vary.

goldsmith_robert

Thanks for the replys, and good suggestions.

The only reason I suggested SRM is that ive been told that the software is better for analysis then powertap. Im quite new to training with power feedback but understand the principles and Im very much persuaded by the evidence (hence this post).

I guess the advantage of powertap would be that individuals could use their own bike on a number of occasions to get several estimates of FTP, including races / TT's. If the accuracy is equivelent to SRM its difficult to justify the extra financial outlay for the club just for the software.

Anyone got experience of powertap vs SRM and care to comment?

Is there another benifit of SRM that im missing?

DaveyL

Re the software, the Poweragent software for the PT is dreadful, but I expect that with the release of their new Joule head unit, the software might get a significant overhaul - it's just a hunch I have, though others more knowledgeable than I may be able to confirm or refute.

However, for power analysis, WKO+ is "the business" and comes in at ~$99 (I think), though the multi-athlete one (which you would probably be wanting) may be more expensive. Again, others will know better than I.

I'd say the advantage of the PT wheel would be that the riders could not just use it for FTP testing, but could train and race with it as well, if they worked out a schedule between themselves - obviously several riders may be taking part in the same race, but there would at least be an element of spreading the PT around.

Alex_Simmons/RST

DaveyL wrote:

Re the software, the Poweragent software for the PT is dreadful, but I expect that with the release of their new Joule head unit, the software might get a significant overhaul - it's just a hunch I have, though others more knowledgeable than I may be able to confirm or refute.

Jesse at Saris has specifically said that the upgraded software will include a calculation of all the metrics that are going to be displayed on the Joule, such as Normalised Power and TSS.

However it is still not available, so one can never be sure until it become available.

James_London

If the upfront cost is an issue, why not rent a few meters from Bob at www.cyclepowermeters.com and spend a little on coaching to get the most out of them?