Figure 2: Upper insert shows positioning of the axial slab within the calf region, from which two phosphorus spectra were acquired. The upper 31P spectrum took twenty seconds to acquire, while the lower one took 11 minutes. Notice that longer acquisitions lead to much better peak resolution. Peaks evident are phosphocreatine (PCr at 0ppm), inorganic phosphate (Pi at 5 ppm), and adenosine triphosphate (ATP between -5 and -20 ppm).