Reactive postural adjustment in response to predictable and unpredictable perturbations in healthy adults: A comparison between swayback, hyperlordotic and erect postures.

BACKGROUND: Promoting an erect posture in standing has been advocated to offer superior protection to the spine when compared to hyperlordotic and swayback postures. RESEARCH QUESTION: Do postural adjustments towards external perturbation differ between erect, hyperlordotic and swayback postures? If so, which posture offers better protection to lumbar spine? METHODS: Forty-four healthy adults received top-down perturbations under unpredictable (without visual-and-auditory input) and predictable (with visual-and-auditory input) conditions in three simulated postures: erect, hyperlordotic, and swayback. Postural adjustments namely the centre of pressure parameters, joint angle onsets, and neuromuscular responses measured by muscle onsets and co-contraction between muscle pairs upon the perturbation were compared using the two-way repeated measures ANOVA. Post-hoc analysis with Bonferroni correction was conducted to identify the between-posture differences for the respective postural adjustment parameters. RESULTS: Path length, ellipse area and average velocity of centre of pressure were significantly greater under unpredictable condition as compared to predictable condition (p < 0.001). Significant between-posture difference was detected in centre of pressure path length (p < 0.035), pelvic tilt onset (p < 0.038) and all muscle co-contraction indexes (p < 0.001). Post-hoc analysis revealed significantly smaller centre of pressure path length in erect posture as compared to hyperlordotic and swayback postures (p < 0.01) under unpredictable conditions. Significantly greater co-contraction indexes of lumbar multifidus and erector spinae, and internal oblique and lumbar multifidus were found in hyperlordotic as compared to erect and swayback postures (p < 0.05). SIGNIFICANCE: Compared to erect posture, adoption of hyperlordotic and swayback postures altered the contributions of the active and passive subsystems of the spine that regulates postural control upon external perturbations. Such differences in neuromuscular control may lessen the capacity of the human spine to withstand loading and shear forces. Prospective studies are required to validate if habitually adopted hyperlordotic and swayback postures contribute to an earlier/ higher prevalence of spinal dysfunctions.

Comparative effectiveness of non-pharmacological interventions on sleep in individuals with chronic musculoskeletal pain: A systematic review with network meta-analysis.

This network meta-analysis aimed to estimate the comparative effectiveness of non-pharmacological interventions on sleep in individuals with chronic musculoskeletal pain. Seven databases were systematically searched up to February 2023. A random-effects network meta-analysis in a frequentist framework was performed to synthesize continuous data as standardized mean differences (SMD) along with a 95% confidence interval (95% CI). A total of 15,641 records were identified, and 107 randomized controlled trials involving 8,121 participants were included. Of 14 identified interventions, eight were significantly more effective than passive control in improving sleep quality at immediate post-intervention (SMDs = 0.67-0.74), with cognitive behavioral therapy (CBT) being the most effective treatment (SMD = 0.74, 95% CI: 0.45-1.03). Only CBT demonstrated sustained effects at short-term (SMD = 1.56; 95% CI: 0.62-2.49) and mid-term (SMD = 1.23; 95% CI: 0.44-2.03) follow-ups. Furthermore, CBT significantly improved subjective (SMD = 0.64; 95% CI: 0.25-1.03) and objective (SMD = 0.30; 95% CI: 0.01-0.59) sleep efficiency compared with passive control at immediate post-intervention. Our findings support CBT as the first-line treatment for improving sleep in individuals with chronic musculoskeletal pain, given its superior effectiveness across multiple sleep outcomes and its sustainable effects until mid-term follow-up. However, the certainty of evidence for these interventions in improving sleep quality was very low to low.