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Revista Dor

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MACHADO, Alessandro Ribeiro de Pádua; OLIVEIRA, Iraides Moraes de; ALVES, Adriano Pereira  and  ANDRADE, Adriano Oliveira. Analysis of the relationship between M wave parameters and pain. Rev. dor [online]. 2011, vol.12, n.4, pp.301-307. ISSN 1806-0013.

BACKGROUND AND OBJECTIVES: Pain is a subjective and individual sensation causing major discomfort. So, it is necessary to put into practice methods to objectively quantify it. Several studies indicate that evoked potentials (EP) generate responses which may reflect painful processes. Our study has used characteristics extracted from the M wave, which is a type of EP related to neuromuscular response, as possible pain sensation markers. METHOD: Participated in this study 13 volunteers, being 6 males and 7 females. Five sessions of an experimental protocol were held. In each session, volunteers received electrical stimulations on the abductor hallucis muscle. Initially, 1 mA current with 20 pulses of 2 Hz was applied. Then, the electric current was incremented in 1 mA until volunteer reported maximum pain. For female volunteers, menstrual cycle day in each session was also recorded. Several M wave characteristics were evaluated. RESULTS: Global minimum of the M wave is correlated to increased electric current amplitude of stimulation, and consequently to more pain felt by the individual. Female participants have reported pain threshold and tolerance with lower electric current intensity as compared to male volunteers. CONCLUSION: Global minimum of the M wave was related to increased pain and in males pain threshold and tolerance were higher as compared to females. Different menstrual cycle phases have not interfered with evaluations.

Keywords : Electric stimulation; Evoked potentials; Pain; Sensory threshold.

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