Agreement between the Stages Cycling and
SRM powermeter systems during field-based off-road climbing

Hurst, HT; Atkins, SJ; Sinclair, JK; Metcalfe, J

Abstract

The aim of this study was to determine the agreement between two portable cycling powermeters for use during field
based mountain biking. A single participant performed 15 timed ascents of an off-road climb. The participants’
bicycle was instrumented with Stages Cycling and SRM powermeters. Mean and peak power output and cadence
were recorded at 1s intervals by both systems. Significant differences were determined using paired t-tests, whilst
agreement was determined by calculating the bias and random error and the associated 95% limits of agreement
(LoA). Significant differences were found between the two systems for mean power output (p<0.001), with the
Stages powermeter under reporting power by 8 ± 1 % compared to the SRM. Bias and random error for mean power
output were -18 ± 7 W (95 % LoA = 12 - 25 W above and below the mean). CV was 5.5 % and 5.2 %, for the Stages
and SRM respectively. Peak power output was significantly lower with the Stages powermeter (p=0.02) by 6 ± 1 %
when compared to the SRM powermeter. Bias and random error for peak power output were -25 ± 74 W (95 % LoA
= 49 – 99 W above and below the mean), whilst CV was 13.7 % and 13.1 %, for Stages and SRM respectively. No
significant differences were found for mean or peak cadence, whilst CV were <3 % for mean cadence for both
systems and <6 % for peak cadence for both systems. This study found that both powermeters provided a reliable
means of recording mean power output and cadence, though peak power values were less reliable. However, the
Stages system significantly underestimated mean and peak power output when compared with the SRM system.
This may in part be due to differences in strain gauges configuration and the subsequent algorithms used for the
calculation of power output and the potential bilateral influences on power output production.

Citation

SRM powermeter systems during field-based off-road climbing. Journal of science and cycling, 4(1), 21-27

• Journal Article Type: Article
• Acceptance Date: Mar 26, 2015
• Publication Date: Jun 1, 2015
• Deposit Date: Dec 7, 2017
• Publicly Available Date: Dec 7, 2017
• Journal: Journal of Science and Cycling
• Electronic ISSN: 2254-7053
• Volume: 4
• Issue: 1
• Pages: 21-27
• Publisher URL: http://www.jsc-journal.com/ojs/index.php?journal=JSC&page=article&op=view&path%5B%5D=162
• Related Public URLs: http://www.jsc-journal.com/ojs/index.php?journal=JSC&page=index