Agreement between the Stages Cycling and PowerTap Powermeter
Keywords:cycling, powermeter, validity, reliability
Several powermeters for almost every type of bicycle are available. The PowerTap (CycleOps) quantifies cycling power and cadence in the rear wheel hub and has already been validated in previous studies. The Stages Cycling Powermeter (Stages Cycling) is lower-priced and more flexible for usage as it measures in the left crank arm. The aim of this study was to determine the agreement between these two devices.
38 participants performed laboratory tests on a stationary roadbike. Power output and cadence were recorded with PowerTap and Stages simultaneously. Differences in power output and cadence were determined. The agreement between methods was quantified by use of mean differences and limits of agreement.
Stages Powermeter underestimates power output by -1.9±4.0%) in comparison to the PowerTap (limits of agreement: 5.9% to -9.7%). Considering cadence, Stages calculates 0.94± 0.16) revolutions per minute more than the PowerTap (limits of agreement: -0.4 to 2.3 rpm). Mean coefficients of variation for power output (50.1%) and cadence (14.2%) estimate good reliability of Stages compared to PowerTap (50.3% and 14.3%).
Despite a systematic bias, Stages can be considered a suitable alternative to measure power output. However, limitations regarding power output measurement have to be respected, especially when cycling with high intensities.
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