Validity and Reliability of the PowerTap Mobile Cycling Powermeter when Compared with the SRM Device

Abstract

The SRM power measuring crank system is nowadays a popular device for cycling power output (PO) measurements in the field and in laboratories. The PowerTap (CycleOps, Madison, USA) is a more recent and less well-known device that allows mobile PO measurements of cycling via the rear wheel hub. The aim of this study is to test the validity and reliability of the PowerTap by comparing it with the most accurate (i.e. the scientific model) of the SRM system. The validity of the PowerTap is tested during i) sub-maximal incremental intensities (ranging from 100 to 420 W) on a treadmill with different pedalling cadences (45 to 120 rpm) and cycling positions (standing and seated) on different grades, ii) a continuous sub-maximal intensity lasting 30 min, iii) a maximal intensity (8-s sprint), and iiii) real road cycling. The reliability is assessed by repeating ten times the sub-maximal incremental and continuous tests. The results show a good validity of the PowerTap during sub-maximal intensities between 100 and 450 W (mean PO difference -1.2 +/- 1.3 %) when it is compared to the scientific SRM model, but less validity for the maximal PO during sprint exercise, where the validity appears to depend on the gear ratio. The reliability of the PowerTap during the sub-maximal intensities is similar to the scientific SRM model (the coefficient of variation is respectively 0.9 to 2.9 % and 0.7 to 2.1 % for PowerTap and SRM). The PowerTap must be considered as a suitable device for PO measurements during sub-maximal real road cycling and in sub-maximal laboratory tests.

The Effect of Variable Gradients on Pacing in Cycling Time-Trials

“…A potential limitation of the study is the reliability of the power meters employed. The PowerTap typically gives a 1.2 % lower power reading compared to the ' gold standard ' SRM with power coe cients of variation (CV) of 1.8 % and 1.5 % respectively [5] . Paton & Hopkins [14] reported similar power CVs of 1.5 % for the PowerTap and 1.6 % for the SRM but more importantly for this study, identiÞ ed the mechanical component of the CVs as 0.9 % and 1.1 % respectively (equivalent to a ~ 0.4 % speed error).…”

Training-Intensity Distribution in Road Cyclists: Objective Versus Subjective Measures

“…HR and PO data were collected during every training session using portable power meters of different brands owned by the cyclists: SRM system (n = 3) (SRM, Jülich, Welldorf, Germany), Power2max (n = 6) (Power2max, Chemnitz, Germany), PowerTap 24 (n = 2) (CycleOps, Madison, USA), SRAM Quarq (n = 1) (SRAM, Chicago, Illinois, USA), Rotor (n = 1) (Rotor bike components, Madrid, Spain), Stages powermeter (n =1) (Stages Cycling, Saddleback LTd., UK) and Pioneer power meter (n = 1) (Pioneer, Kawasaki, Kanagawa, Japan). Validity of all the crank based mobile power meters was assessed by comparing the measured power output by the mobile power output to the set power output by the ergometer (Cyclus2 ergometer, RBM Electronics, Leipzig, Germany) during every stage of the incremental test.…”

Historical Improvement in Speed Skating Economy

“…However, mechanical power output cannot be measured directly during speed skating, as can be done during cycling. 6,7 Only by calculating the power losses due to ice and air friction during skating at a constant velocity, can an indirect estimate of mechanical power output be obtained. 8,9 Because of the difficulties with directly measuring skating efficiency, an alternative measure, skating economy, defined as the submaximal V̇O 2 expressed in mL•kg -1 •km -1 , 10 can be used.…”