A study in the accuracy and precision of determining the moment of inertia for an ergometer flywheel

The purpose of this study was to establish the accuracy and precision for determining the moment of inertia of the flywheel of a friction loaded ropebraked ergometer. An accurate assessment of the moment of inertia is required to correct the power output of subjects undertaking tests such as the Wingate Anaerobic Test (WAnT). In this study the moment of inertia of a Monark 824E Ergometer was obtained using the current British and European
Standard test and the results were compared with values obtained using a commercially available WAnT correction system. This is a standard piece of equipment used by physiologists to correct work expended values of subjects in order to account for the additional work requirements caused by the moment of inertia of the ergometer flywheel. The WAnT correction system results were compared with results obtained using data from a Tachometer. The calibration procedure for the WAnT correction system was followed and simultaneously the flywheel speed was recorded using the Tachometer. The moment of inertia obtained using the procedure outlined by the British and European Standard was
found to be 0.8 kgrn 2 (SD 0.0085). Using the WAnT correction system the moment of inertia was given as 1.1792 kgm 2 (SD 0.233) and 0.8194 kgm2 (SD 0.001) using the Tachometer. It was found that repeatability using the commercial correction software was poor. The method used by the WAnT correction system for
calculating the frictional resistance of the system gives incorrect values which are much higher than the actual frictional resistance. Thus the use of the data provided by the WAnT Correction system to correct work expended values from athletes can lead to inaccurate physiological results.