RESUMO
Neuromuscular electrical stimulation can be used to increase strength of skeletal muscle. In neuromuscular electrical stimulation of innervated skeletal muscle, the application of the highest possible intensities of electricity is an important determinant of therapeutic success with regard to strength training. The therapeutic goal of "strengthening muscles" is opposed to the side effect of discomfort through the application of electricity. The aim of the present study was to compare three forms of electric current with respect to subjective tolerance and maximum achievable muscular strength. Twenty-nine healthy male volunteers were included in a single-blind study in which three forms of electric current were applied in a randomized fashion. The following types were compared: a short monophasic form, a biphasic form that was twice as long in terms of impulse duration, and a long monophasic form with an equal impulse duration than tht of the biphasic form and with an impulse form that corresponded to the short monophasic current. Stimulation was administered via surface electrodes placed on the knee extensors in the lower extremity on the right side. The intensity of the current was increased to the individual limit of tolerance or to a maximum of 100 mA. The main target parameter used to determine the success of treatment was the maximum electrically induced strength as a percentage of maximal voluntary contraction. The short monophasic form of electricity was associated with much less discomfort than the long monophasic and biphasic forms (p < 0.0001, p = 0.0062). Furthermore, the biphasic form was better tolerated (and therefore had a larger therapeutic range of application) than the long monophasic form (p = 0.041). The biphasic and long monophasic forms produced higher values for maximum electrically induced strength than did the short monophasic form (p = 0.0001, p = 0.0010). To summarize: the biphasic form had a larger range of therapeutic application than the long monophasic form. Furthermore, the biphasic form produced 40% more electrically induced strength than the short monophasic one. It may be concluded that, in terms of therapeutic application, the biphasic form of electric current is superior to the monophasic forms described in the present study.
Assuntos
Terapia por Estimulação Elétrica/métodos , Estimulação Elétrica Nervosa Transcutânea/métodos , Adulto , Condutividade Elétrica , Humanos , Contração Isométrica/fisiologia , Masculino , Dose Máxima Tolerável , Músculo Esquelético/inervação , Junção Neuromuscular/fisiologia , Medição da Dor , Resultado do TratamentoRESUMO
BACKGROUND AND METHODS: Pulsed magnetic field therapy is frequently used to treat the symptoms of osteoarthritis, although its efficacy has not been proven. We conducted a randomized, double-blind comparison of pulsed magnetic field and sham therapy in patients with symptomatic osteoarthritis of the knee. Patients were assigned to receive 84 sessions, each with a duration of 30 minutes, of either pulsed magnetic field or sham treatment. Patients administered the treatment on their own at home, twice a day for six weeks. RESULTS: According to a sample size estimation, 36 consecutive patients were enrolled. 34 patients completed the study, two of whom had to be excluded from the statistical analysis, as they had not applied the PMF sufficiently. Thus, 15 verum and 17 sham-treated patients were enrolled in the statistical analysis. After six weeks of treatment the WOMAC Osteoarthritis Index was reduced in the pulsed magnetic field-group from 84.1 (+/- 45.1) to 49.7 (+/- 31.6), and from 73.7 (+/- 43.3) to 66.9 (+/- 52.9) in the sham-treated group (p = 0.03). The following secondary parameters improved in the pulsed magnetic field group more than they did in the sham group: gait speed at fast walking [+6.0 meters per minute (1.6 to 10.4) vs. -3.2 (-8.5 to 2.2)], stride length at fast walking [+6.9 cm (0.2 to 13.7) vs. -2.9 (-8.8 to 2.9)], and acceleration time in the isokinetic dynamometry strength tests [-7.0% (-15.2 to 1.3) vs. 10.1% (-0.3 to 20.6)]. CONCLUSION: In patients with symptomatic osteoarthritis of the knee, PMF treatment can reduce impairment in activities of daily life and improve knee function.