Figure 1.

Creatine chemical exchange saturation transfer (CrCEST) maps of exercise‐induced changes in skeletal muscle creatine (Cr) concentration. Data displayed are from one healthy 36‐year‐old male following 2 min of plantar flexion exercise against 7 PSI pressure at 0.75 Hz. Top panel: CrCEST maps before (enclosed by white box) and after exercise show an increase in CrCEST asymmetry (increase in red shading), indicative of increased free Cr, liberated as part of the phosphocreatine shuttle to generate ATP ( PCr + ADP ↔ Cr + ATP ). During recovery, free Cr decreases as the ATP produced by oxidative phosphorylation shifts the reaction towards PCr regeneration. Bottom panel: Changes in CrCEST asymmetry before and after exercise are highlighted in prescribed regions of interest: lateral gastrocnemius (green), medial gastrocnemius (red), and the soleus (blue) muscles. Data are displayed as mean ± SD at each time point. The mean at each time point represents the average value from all activated voxels, and its standard deviation, from within each muscle.