We extended an interleaved 1H/31P multi-voxel sequence for simultaneous pH monitoring based on carnosine (pH1H, PRESS) and Pi (pH31P, semi-LASER) with a co-localized dynamic water reference (PRESS). Simultaneous pH evaluations were done at 3 T in the soleus and gastrocnemius muscles during a straight-leg plantar flexion paradigm. A pH1H bias of ~0.05 units was removed by using the dynamic water reference. pH1H and pH31P time courses (1-minute temporal resolution) were comparable. Pi and Carnosine (C2-H) resonances broadened during exercise in the gastrocnemius. This method opens the way for new applications in functional studies targeting individual muscles at 3 T.