Creatine CH2 and PCr dynamics closely correlate in dynamic interleaved MRS of exercising muscle

Motivation: To explore quantification of skeletal muscle oxidative metabolism by 1H MRS. Goal(s): We used the increased accuracy of 7T MRS with a dedicated RF-coil, interleaved acquisition and localization of 31P information to compare Creatine-CH2 and Phosphocreatine time courses during exercise and recovery. Approach: Eight volunteers were measured on a 7T MR system with RF-coil and ergometer dedicated for exercise. 1H and 31P MR spectra were acquired interleaved during exercise and recovery. Results: Exercise led to disappearance of the Creatine-CH2 resonance, while the CH3 resonance remained stable during exercise. The recovery time constants were similar (τPCr=37±9s and τCr=34±6s) and positively correlated. Impact: The time course of the Creatine-CH2 resonance in skeletal muscle can be accessed via dynamic 1H MRS. If accurately reflecting oxidative metabolism, this technique has the potential to render non-invasive metabolic studies broadly accessible, without needing multi-nuclear MRI capabilities.