RESUMO
Objective: The present study aimed to investigate if a new placebo device for interferential current (IFC) that delivers current during only the first 40 seconds of stimulation is effective at promoting adequate subject blinding. Methods: Seventy-five subjects were recruited and enrolled into three groups: active IFC, inactive placebo, and new placebo. Pressure pain threshold (PPT), cutaneous sensory threshold (CST), and pain intensity were measured before and after the intervention. After the final assessment, the subjects and the investigator who applied the current were asked about the type of stimulation administered. Results: None of the placebo forms studied resulted in significant changes to PPT, CST, or pain intensity. The subjects stimulated with active IFC at high intensities (> 17 mA) of stimulation showed higher PPT and CST and lower pain intensity than subjects stimulated at low intensities ( p < 0.03). The new placebo method blinded the investigator in 100% of cases of IFC and 60% of subjects stimulated, whereas for inactive placebo, the investigator was blinded at a rate of 0% and 34% of subjects. Conclusion: The new method of placebo IFC was effective for blinding of research investigators and most of the active IFC-treated subjects, promoting an appropriate placebo method.
