Accuracy of SRM and power tap power monitoring systems for bicycling

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. doi:10.1249/01.MSS.0000132380.21785.03

Author Gardner, A. S.
Stephens, S.
Martin, D. T.
Lawton, E.
Lee, H.
Jenkins, D.
Title Accuracy of SRM and power tap power monitoring systems for bicycling
Journal name Medicine And Science In Sports And Exercise   Check publisher's open access policy
ISSN 0195-9131
Publication date 2004
Sub-type Article (original research)
DOI 10.1249/01.MSS.0000132380.21785.03
Volume 36
Issue 7
Start page 1252
End page 1258
Total pages 7
Editor K. B. Pandolf
Place of publication Philadelphia, PA
Publisher Lippincott Williams & Wilkins
Collection year 2004
Language eng
Subject C1
321401 Exercise Physiology
750203 Organised sports
Abstract Purpose: 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.
Keyword Sport Sciences
Cycling Performance
Dynamic Calibration
Q-Index Code C1

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Created: Wed, 15 Aug 2007, 03:18:46 EST