Introduction to in vivo P-31 magnetic resonance spectroscopy of (human) skeletal muscle

P-31 magnetic resonance spectroscopy (MRS) offers a unique non-invasive win dow on energy metabolism in skeletal muscle, with possibilities for longitu dinal studies and of obtaining important bioenergetic data continuously and with sufficient time resolution during muscle exercise. The present paper provides an introductory overview of the current status of in vivo P-31 MRS of skeletal muscle, focusing on human applications, but with some illustra tive examples from studies on transgenic mice. Topics which are described i n the present paper are the information content of the P-31 magnetic resona nce spectrum of skeletal muscle, some practical issues in the performance o f this MRS methodology, related muscle biochemistry and the validity of int erpreting results in terms of biochemical processes, the possibility of inv estigating reaction kinetics in vivo and some indications for fibre-type he terogeneity as seen in spectra obtained during exercise.