Manual therapy, such as spinal manipulation (SM), is commonly used to treat non-specific chronic low back pain (CLBP), although its mechanisms remain poorly understood. It has been hypothesized that the mechanical forces applied during spinal manipulation (SM) influence proprioceptive function, which is often impaired in patients with CLBP. This study aimed to investigate the effect of a single SM intervention on lumbar proprioceptive function and its potential relationship with analgesic effects in patients with CLBP. In a single-blind randomized controlled trial, data from 142 adults with or without CLBP were analyzed after random assignment to receive lumbar spinal manipulation (LMANIP), lumbar mobilization (LMOB), or no intervention (NI). The primary outcome was the proprioceptive weighting (PW) ratio, which reflects the central nervous system's preferred source of proprioceptive input for balance control, specifically from the lumbar and ankle muscles. PW ratios were assessed immediately before and after intervention by analyzing postural sway changes during vibrotactile stimulation (60 Hz). PW changed in both healthy participants and patients after the intervention, with a significantly stronger lumbar-steered PW following LMANIP compared to NI (β = -0.047, t(422) = -2.71, p = 0.007) and LMOB (β = -0.039, t(422) = -2.17, p = 0.030). Moreover, LMANIP was particularly effective in reducing pain in patients with stronger lumbar-steered PW before intervention (p < 0.017). These findings suggest that a single SM session enhances proprioceptive input from the lumbar muscles and that the strength of the analgesic effect is associated with the baseline PW status.

The authors have declared no competing interest.

NCT04869514

This project was funded by the European Centre for Chiropractic Research Excellence (ECCRE) and the Balgrist Foundation.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the Swiss local ethics board 'Kantonale Ethikkommission Zurich, KEK' (Nr. 2021-01331). All procedures adhered to the Declaration of Helsinki and current legislation pertaining to the management of personal data.

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All datasets analyzed in this study are available in the main text or upon request. Further information and requests should be directed to the corresponding author, Michael L Meier at the following e-mail address: michael.meier@balgrist.ch and will be considered on a case-by-case basis, in accordance with the local policies of the sponsor and the relevant Swiss and European Union data protection and privacy legislation.