Technical note: MR-compatible pedal ergometer with electromechanical pedal resistance and exercise triggering enhanced by visual feedback via video display

Background: During and after exercise,dynamic 31P MR parameters are typ
ically measured using an MR-compatible ergometer. Self-built equipment for
 local condition can be constructed where possible.
 Purpose:To develop a pedal resistance ergometer with rocker arm based on a
 system that combines electric weight displacement,visual self-monitoring,and
 exercise triggering. The repeatability and reproducibility were tested.
 Methods:The hardware and software for the ergometer were constructed from
 commercial components in a home laboratory. Twelve volunteers participated
 in the testing of the ergometer.
 Results: A fully automated ergometer system was developed, allowing the
 pedal resistance to be adjusted during the examination. The system includes
 a self-monitoring and triggering mechanism that enables both the operator and
 subject to monitor pedal frequency and force.The operator can modify the pedal
 resistance as desired during the exercise. This self-monitoring solution is sim
ple and cost-effective, requiring only a commercial potentiometer, an Arduino
 converter, and a conventional video projector with a personal computer (PC).
 Additionally,all system components are located outside the magnetic resonance
 (MR) room,avoiding interference with the MR system.Results of several test of
 the reproducibility/repeatability of power at three pedal resistance values (15%,
 24%,25%maximalvoluntaryforce)wereexpressedbothasacoefficientof vari
ation ranging from 6% to 3.1% and as an intraclass correlation of coefficient
 ranging from 0.96 to 0.99. Similar values were also found for other dynamic
 parameters of 31P MR spectroscopy. These findings are similar to published
 data obtained on different types of ergometers.
 Conclusions: Based on more than 1 year of usage,the ergometer proved suc
cessful in handling stationary and variable loads,and can be easily operated by
 a single user.