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Revista de Sanidad Militar de las FAS 71_4

Effectiveness of neuromuscular electrical stimulation in the functional knee rehabilitation in soldiers Sanid. mil. 2015; 71 (4)  243 Role of Military Physical Therapists in Recent Combat Campaigns Now, we show quantitatively important of physiotherapy in the army from 2005 to 2011. DISCUSSION As a method of functional knee rehabilitation in soldiers, NMES represents a promising alternative to traditional exercises to syste-matically improve strength parameters and motor skills. Scientific evidence shows that subjects whose aim is to gain therapeutic or functional strength, combining NMES with controlled and directed exercise should work. Size of the electrodes, waveform and associated parameters for NMES Forrester & Petrofsky examined the effect of the size and shape of the electrode, waveform and associated pain response during NMES18. This research showed that there was little difference between the size or shape of the electrode and the development of quadriceps strength in a NMES. This was surprising because, intuitively, a larger electrode should recruit more motor units in the muscle since NMES was dispersed over a larger muscle area19. However, it was shown that the sine wave modulated type was more effective than stimulation by a square or rectangular wave in obtaining muscle contraction with significant potential recruit-ment20. Another factor to consider is the spacing of the electrodes in the NMES. Petrofsky et al. studied this stimulation with different frequencies, size of the electrodes, current amplitudes, and pulse widths. The results were that changes in the stimulation pulse width and frequency had little effect on the penetration depth of the cur-rent in the muscle but it induced pain. However, this does not mean that the wider pulse widths do not transfer more power to the motor nerves that innervate the muscles and therefore allow a strong mus-cle contraction21,22. The parameters that influence the penetration of the current were: 1. The spacing of the electrodes alter the penetration depth: When the electrodes had a 10 cm or less of difference regardless if the electrode was large or small, the current was significantly high-er in the central line between electrodes23. Furthermore, the current penetration into the muscle was greater. Therefore, to stimulate a quadriceps muscle, the electrode placement must be specific and the distance between them must be small. 2. Stimulation by a sine wave has different current transfer char-acteristics compared to the rectangular wave stimulation: While on the skin, the change of sinusoidal or rectangular did not deliver any difference in currents; in muscle stimulation sine wave created between 25-50% more current than did stimulation by rectangular wave. This explanation may be related to the fat layer. The fat layer forms a dialectric strength because of its high electrical resistance; high capacitance is developed by the high conductivity of the skin and muscle driven by the separation of the fat24,25. Therefore, the sine wave passes through a condenser without altering the energy field, while a rectangular wave changes shape by passing through a filter capacitor and loses energy25,26, which would lead to an increase in the amplitude and cause pain18. Placement of electrodes: Comfortable quadriceps muscle contraction Regarding the placement of the electrodes, the evidence con-firms the influence of the positioning of the electrodes and their relationship with the perception of discomfort and/or pain during stimulation NMES, and the relationship between the depth of sti-mulation sites and mechanical-metabolic response-induced qua-driceps muscle27,28. The motor point stimulation on muscle causes increased muscle metabolic mechanical stress, which represents the basic factors for muscle strengthening and adaptation. It also means that the motor point stimulation causes the stimulus to be more bearable, avoiding rapid onset of fatigue induced by sustai-ned tetanic stimulation27,29. The size of the electrode, as we have discussed above, is not directly related to the degree of muscle contraction or the perceived pain. But qualifying the latter, it is very important that the choi-ce of electrodes is suitable to the area to be stimulated and if we use very small electrodes to stimulate a large area, the amplitude has to be high and can cause painful stimulation before reaching a sufficient quadriceps muscle contraction to allow strength training30. Therefore the selection of appropriate electrode size is essential for comfortable stimulation, all with specific electrode placement on the muscle motor to reduce the required amplitude threshold point. Signal analysis: Placement of electrodes at Point Motor vs Placement according to the book for the equipment To analyse the signal, the contractile parameters were evalua-ted: peak contraction, tetanus tension and tension-time area, cal-culated as the area between the baseline and the voltage signal27,28. To study the metabolic disturbances induced by contractions eli-cited with both forms of stimulation, oxy-hemoglobin (O2Hb) was measured, the deoxy-hemoglobin (HHB), the tissue oxygenation index (TOI), and the total index normalized hemoglobin (THI). Referring to the baseline, the greater the corresponding negative change during contraction values were O2Hb, TOI and THI; and corresponding to the largest positive change values during the re-covery period were HHB and THI27. So it is shown that when the motor point is stimulated, mechanical and metabolic stress on the quadriceps muscle is greater27. The method of stimulation is a key factor in determining the muscle induced functional improvements NMES. Unlike when fo-llowing the instructions which come with the equipment, which is adopted by most professional and non-professional users, the mode motor point stimulation elicited significantly higher mechanical res-ponses evaluated by the peak voltage during single twitches; maxi-mum tetanic tension; and the area under the time-voltage curve27. In particular, the voltage-time area has proved to be adequate for estimating the actual work performed by the motor unit recruitment parameter and, therefore, to predict the effectiveness of quadriceps muscle contraction. The scientific evidence says that this area is pro-


Revista de Sanidad Militar de las FAS 71_4
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