Metabolic changes following neuromuscular electrical stimulation
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SUMMARY Purpose The thesis exists of two parts. In the first part the results of trials focused on enzyme activity, motor unit recruitment and changes in fiber type distribution in human lower limb muscle following neuromuscular electrical stimulation (NMES). Secondly, the metabolic response and symptom perception are compared of low-frequency NMES and high-frequency NMES of the quadriceps femoris muscles in patients with COPD. Methods A systematic review was performed to identify relevant trials, the methodological quality of these trials was scored and the literature was analyzed qualitatively using a best-evidence synthesis. In a prospective study the metabolic response (expressed in peak oxygen uptake and peak minute ventilation) and symptom perception (expressed in Borg symptom scores for dyspnoea and leg fatigue) were assessed during a low-frequency NMES session and a high-frequency NMES session. Results Most of the trials, included in the systematic review, report changes in enzyme activity and there are obvious changes in skeletal muscle shift following NMES. The results concerning the rank order of motor unit recruitment during NMES are conflicting. In the prospective study, the median peak oxygen uptake during the low-frequency NMES session was significantly higher compared to the high-frequency NMES session. The median minute ventilation and symptom Borg scores for dyspnoea and leg fatigue did not significantly differ between both NMES sessions. Conclusion From the viewpoint of this systematic review NMES looks promising as a useful training modality because of its changes in enzyme activity and its influence on muscle fiber shift. Also, the metabolic response and symptoms of dyspnoea and leg fatigue were low during as well low-frequency and high-frequency NMES sessions among patients with COPD.