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.
The critical shoulder angle and its correlation with rotator cuff tears and alternatively glenohumeral osteoarthritis has become a popular research topic in recent years. With carefully standardized x-rays, a correlation emerges. This development has generated interest in potential clinical usefulness for this measurement, as well as possible surgical interventions to modify the course of these shoulder problems. Lateral acromioplasty may have a role in rotator cuff surgery, but early study results are mixed. Prophylactic lateral acromioplasty has been proposed but would not be evidence based at this time, and there could be unintended negative consequences. For now, accurate x-ray films and awareness of the critical shoulder angle by the clinician could impact the index of suspicion and also may prove useful in patient counseling for these 2 shoulder diseases.
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