Simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy measurements of the lumbar back muscle during...

The aim of this study was to demonstrate the feasibility of simultaneous surface electromyography (SEMG) and 31P-MR spectroscopy (31P-MRS) measurements on the back muscle of volunteers during the performance of an isometric exercise. Six volunteers (three male, three female) performed a modified Biering-Sörensen test inside a 1.5 T MR scanner while simultaneously recording SEMG signals. A surface coil was used for 31P-MRS with a CSI sequence. Spectra were collected with a voxel resolution of 40 mm x 40 mm x 100 mm and a temporal resolution of 30 s during periods of rest, sustained muscle contraction and recovery. The duration of muscle contraction was 150 s. SEMG analysis yielded a decrease of the mean SEMG frequency of approximately 20%. The SEMG amplitudes were constant or increased up to approximately 150% during exercise. 31P-MRS showed a maximum decrease of the phosphocreatine (PCr) amplitude down to approximately 32% of its initial value. Simultaneously, a doubling of the inorganic phosphate (Pi) signal was observed. The present study demonstrates that simultaneous SEMG and 31P-MRS measurements of the back muscle are feasible during isometric exercises.