RESUMO
OBJECTIVE: This study investigated the effect of spinal manipulative therapy (SMT) on the singing voice of male individuals. STUDY DESIGN: Randomized, controlled, case-crossover trial. METHODS: Twenty-nine subjects were selected among male members of the Heralds of the Gospel. This association was chosen because it is a group of persons with similar singing activities. Participants were randomly assigned to two groups: (A) chiropractic SMT procedure and (B) nontherapeutic transcutaneous electrical nerve stimulation (TENS) procedure. Recordings of the singing voice of each participant were taken immediately before and after the procedures. After a 14-day period, procedures were switched between groups: participants who underwent SMT on the first day were subjected to TENS and vice versa. Recordings were subjected to perceptual audio and acoustic evaluations. The same recording segment of each participant was selected. Perceptual audio evaluation was performed by a specialist panel (SP). Recordings of each participant were randomly presented thus making the SP blind to intervention type and recording session (before/after intervention). Recordings compiled in a randomized order were also subjected to acoustic evaluation. RESULTS: No differences in the quality of the singing on perceptual audio evaluation were observed between TENS and SMT. CONCLUSIONS: No differences in the quality of the singing voice of asymptomatic male singers were observed on perceptual audio evaluation or acoustic evaluation after a single spinal manipulative intervention of the thoracic and cervical spine.