ELECTRICAL-STIMULATION OF HUMAN-MUSCLE STUDIED USING P-31 NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY

This study used phosphorous nuclear magnetic resonance (**3**1P-NMR) spectroscopy to examine the metabolic demand resulting from electrical muscle stimulation (EMS) applied to human skeletal muscle. For each of six subjects, the forearm flexor muscle group was monitored with **3**1P-NMR during both maximum voluntary and 6-s EMS-induced contractions. A simple protocol using a tourniquet was added in one subject to assess the role of blood flow in this model. Eight hertz (nontetanic) EMS showed less (p less than 0. 025) depletion of phosphocreatine (36%) than did tetanic 70-Hz EMS (60%), voluntary isometric (66%), and voluntary isokinetic (68%). The results of the tourniquet studies suggested that the nontetanic EMS allowed relatively increased muscle blood flow and oxygen supply during contraction. Tetanic EMS provided a similar metabolic demand to that of conventional resistive exercise, as measured by **3**1P-NMR spectroscopy.