Endocrine response after cervical manipulation and mobilization in people with chronic mechanical neck pain: a randomized controlled trial

BACKGROUND: Most of the research on the effects of spinal manipulation on endocrine function has been done on healthy subjects and has yielded contradictory results. The potential role of cervical manual therapy intervention in order to induce changes in the endocrine system has not yet been investigated. AIM: The aim of this trial is to compare the effects on salivary cortisol levels and clinical outcomes of cervical manipulation versus cervical mobilization or sham manipulation in patients with chronic mechanical neck pain. DESIGN: Randomized controlled trial. SETTING: University of Alcala de Henares: outpatient (referrals from office workers). POPULATION: A total of 83 patients with chronic mechanical neck pain. METHODS: Participants were randomized to receive one session of cervical manipulation, cervical mobilization, or sham manipulation. The measured variables were salivary cortisol levels, neck pain and disability, pressure pain thresholds (PPT), and cervical range of motion (ROM). They were obtained at baseline, immediately after treatment (except neck disability), and at one-week follow-up (except cortisol). RESULTS: A significant and comparable increase in cortisol levels was observed immediately after cervical manipulation and mobilization (both P<0.001). Neck disability improved to a similar degree in the cervical manipulation and mobilization groups at the one-week follow-up (both P<0.001). Neck pain was reduced immediately after cervical manipulation (P<0.001), cervical mobilization (P=0.001), and sham manipulation (P<0.001). There were no significant changes in most ROM directions after either treatment. No significant interaction effect was observed for PPT. CONCLUSIONS: Cervical manipulation and mobilization resulted in a similar increase in cortisol concentrations immediately post-treatment in people with chronic mechanical neck pain. Supraspinal mechanisms may thus play a role in the hypoalgesic effects that follow the application of both interventions. CLINICAL REHABILITATION IMPACT: The increase in cortisol levels was similar with cervical manipulation and mobilization so induced stress levels can be similar in both interventions.