This study describes the methodological developments to both convert and transmit several mechanical signals in a magnetic environment (3T Verio Siemens) as optical signals. Multiple sensors were connected to a MR-compatible ergometer used to assess dynamic knee extensions kinetics. The corresponding signals were analog to digital converted and transmitted as optical signals through a single optical fiber. The quality of mechanical and 31P MR spectroscopy (31P-MRS) signals remained high and disclosed no adverse interference from the transducers ensuring both conversion and transmission. The multiplexed signals transmission allowed an accurate assessment of human movement kinetics in a magnetic environment.