• Bakken AG
• Eklund A
• Hallman DM
• Axén I

• Affiliation / Karolinska Institutet. Institute of Environmental Medicine. Unit of Intervention and Implementation Research for Worker Health
• Affiliation / University of Gävle. Department of Occupational and Public Health Sciences. Centre for Musculoskeletal Research
• Affiliation(G) / Sweden / Gävle
• Affiliation(G) / Sweden / Stockholm
• Autonomic Nervous System
• Heart Rate
• Muscle Stretching Exercises
• Musculoskeletal Manipulations
• Neck Pain
• Open Access Document
• Random Allocation

Background: Persistent or recurrent neck pain is, together with other chronic conditions, suggested to be associated with disturbances of the Autonomic Nervous System. Acute effects on the Autonomic Nervous System, commonly measured using Heart Rate Variability, have been observed with manual therapy. This study aimed to investigate the effect on Heart Rate Variability in (1) a combination of home stretching exercises and spinal manipulative therapy versus (2) home stretching exercises alone over 2 weeks in participants with persistent or recurrent neck pain.

Methods: A randomized controlled clinical trial was carried out in five multidisciplinary primary care clinics in Stockholm from January 2019 to April 2020. The study sample consisted of 131 participants with a history of persistent or recurrent neck. All participants performed home stretching exercises daily for 2 weeks and were scheduled for four treatments during this period, with the intervention group receiving spinal manipulative therapy in addition to the home exercises. Heart Rate Variability at rest was measured at baseline, after 1 week, and after 2 weeks, with RMSSD (Root mean square of successive RR interval differences) as the primary outcome. Both groups were blinded to the other group intervention. Thus, they were aware of the purpose of the trial but not the details of the “other” intervention. The researchers collecting data were blinded to treatment allocation, as was the statistician performing data analyses. The clinicians provided treatment for participants in both groups and could not be blinded. A linear mixed-effects model with continuous variables and person-specific random intercept was used to investigate the group-time interaction using an intention to treat analysis.

Results: Sixty-six participants were randomized to the intervention group and sixty-five to the control group. For RMSSD, a B coefficient of 0.4 (p value: 0.9) was found, indicating a non-significant difference in the regression slope for each time point with the control group as reference. No statistically significant differences were found between groups for any of the Heart Rate Variability indices.

Conclusion: Adding four treatments of spinal manipulation therapy to a 2-week program of daily stretching exercises gave no significant change in Heart Rate Variability.

Trial Registration: The trial was registered 03/07/2018 at ClinicalTrials.gov, registration number: NCT03576846. 

Author keywords: Manipulative therapy — Stretching exercises —  Heart Rate Variability —  HRV —  Autonomic nervous system

Author affiliations: AGB, AE, IA: Department of Environmental Medicine, Division of Intervention and Implementation Research for Worker Health, Karolinska Institutet, Stockholm, Sweden; DMH: Centre for Musculoskeletal Research (CBF), Department of Occupational Health Sciences and Psychology, University of Gävle, Gävle, Sweden
Corresponding author: Anders Galaasen Bakken—Anders.Galaasen.Bakken@ki.se

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