A crossover study on the effect of cervical mobilization on motor function and pressure pain threshold in pain-free individuals.

OBJECTIVE: Cervical mobilization has been shown to elicit effects on pain perception, autonomic function, and motor function in subjects who experience musculoskeletal pain. The improvement in motor function may be a direct effect of the treatment or secondary to a hypoalgesic effect. This study tested whether it is possible to alter motor function following joint mobilization in situations where motor performance is not impaired by pain. METHODS: Twenty-four asymptomatic subjects participated in this double-blind, controlled, within-subjects crossover study. Pressure pain thresholds and electromyographic activity of the superficial neck flexor muscles were compared with repeated-measures analysis of variance between a posteroanterior cervical mobilization, manual contact, and noncontact condition. RESULTS: The results indicate no significant change in the pressure pain threshold (P =.846) after posteroanterior cervical mobilization. There was no significant difference in superficial neck flexor muscle activity during the craniocervical flexion test (P =.713). Post hoc power analysis demonstrated the ability to detect a 15% difference in electromyographic activity with 70% power. CONCLUSION: The improvement in motor function demonstrated in previous studies was not replicated, suggesting that either it is only possible to produce an effect when motor function is impaired or the change in motor function is secondary to the pain inhibitory effect of the treatment.