The contribution of NMR, NIRS and their combination to the functional assessment of human muscle

In the last decade the study of the human muscle mechanics and energetics in physiology and pathology underwent a radical change. Indeed, the use of biopsy is being progressively accompanied by non-invasive techniques which allow a more integrative assessment of muscle function in vivo. Magnetic resonance imaging (MRI) provides a better insight into muscle structure down to the fascicular level, proving to be an essential source of information, particularly for the study of biomechanics. Magnetic resonance spectroscopy (MRS), besides the study of muscle anaerobic (high energy phosphate compounds by P-31 and H-1) and aerobic metabolism as well as of metabolic control, makes it possible to follow the time course of glycogen concentration (C-13) as a function of exercise intensity and duration and of its recovery both in healthy trained and untrained subjects and in diabetic patients. Near-infrared spectroscopy (NIRS) allows to assess muscle oxidative metabolism, providing changes of total, deoxy-and oxy-hemoglobin in the resting and contracting muscle. The concomitant use of the above techniques is expected to provide a synergic functional picture of the human muscle that is complementary to the structural and ultrastructural microscopic approach.