Detection of muscle injury in humans with 31‐P magnetic resonance spectroscopy

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Abstract
Strenuous exercise can result in muscle injury that may persist for 2 weeks. Our purpose was to determine if muscle injury can be detected with 31‐P magnetic resonance spectroscopy. Normal subjects performed repeated lengthening contractions with either arms or legs designed to result in mild muscle injury. One hour after the arm exercise, there was a significant increase in the inorganic phosphate to phosphocreatine ratio (Pi/PCr), with the maximum increase in Pi/PCr occurring 1 day postexercise (0.12 ± 0.01 to 0.21 ± 0.05). Pi/PCr remained elevated for 3–10 days. Similar results were seen following the leg exercise protocol. ATP/(Pi+PCr) decreased in all the arm exercised subjects. Exercise protocols that did not contain lengthening contractions did not result in changes of Pi/PCr or ATP/(Pi+PCr). Patients with various neuromuscular diseases with evidence of muscle damage (elevated CK, muscle soreness, and histopathological findings) also showed increased Pi/PCr at rest. We conclude that elevated Pi/PCr at rest can reflect nonspecific muscle damage in normal and diseased subjects.