Electrical stimulation of human muscle studied using 31P-nuclear magnetic resonance spectroscopy.

This study used phosphorous nuclear magnetic resonance (31P-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 31P-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 31P-NMR spectroscopy.

Chronic exertional compartment syndrome: correlation of compartment pressure and muscle ischemia utilizing 31P-NMR spectroscopy.

In the past 5 years, a great deal of time and effort has been expended in an effort to better define clinical, anatomic, and laboratory parameters of CECS. It is now a well-recognized entity and one that can be readily resolved with fasciotomy. But the reasons for predisposition and the pathophysiologic mechanisms remain obscure. It appears, however, that basing the decisions for fasciotomy on clinical characteristics alone leads to overdiagnosis and excessive surgery. In this series, almost 50% of the referred subjects failed to demonstrate adequate laboratory criterion for the diagnosis of CECS. Fasciotomy in these patients may have effected a cure, but the reasons may be unrelated to increased intracompartmental pressure. Furthermore, in the laboratory diagnosis of CECS, the rate of return to resting compartment pressure following exercise seems more accurate than reliance on resting pressure alone. 31P-NMR has proved valuable in the dynamic assessment of muscle ischemia as reflected by relative PCr concentrations. Finally, although a mechanism explaining the source of pain has not been established by this study, it appears that ischemia is not a significant factor.