Keeping the abdomen relaxed versus contracted during Pilates improves disability slightly and may improve other outcomes in chronic non-specific low back pain: a randomised trial

QUESTION: In patients with non-specific chronic low back pain, what is the effect of education to keep the abdomen relaxed versus contracted during Pilates exercises on pain intensity, disability, function and global perceived effect? DESIGN: Two-group, parallel, randomised trial with concealed allocation and intention-to-treat-analysis. PARTICIPANTS: A total of 152 patients with non-specific chronic low back pain participated in the trial. INTERVENTION: All participants were randomised to one of two groups and treated with Pilates exercises for 12 weeks (twice a week for 60 minutes). The control group (n = 76) received guidance on the specific activation of the core muscle group-primarily the abdominals, pelvic floor, diaphragm and deep spinal muscles-while the experimental group (n = 76) received guidance to perform the exercises in a relaxed and smooth way. OUTCOME MEASURES: Primary outcomes were pain intensity and disability at 12 weeks. Secondary outcomes were patient-specific function and global improvement at 12 weeks. RESULTS: Compared with keeping the abdomen contracted during Pilates, education to keep it relaxed led to these adjusted mean differences: change on the 0-to-10 pain scale (-0.6, 95% CI -1.4 to 0.2), change on the 0-to-24 disability scale (-1.4, 95% CI -2.6 to -0.2), change on the 0-to-10 patient-specific function scale (0.3, 95% CI -0.3 to 0.9) and final score on the -5 to +5 global perceived effect (0.6, 95% CI -0.1 to 1.2). CONCLUSION: Education to relax the abdominal muscles during Pilates exercises resulted in slightly greater improvement in disability compared with Pilates with education to keep the abdomen contracted. For the other outcomes (pain, patient-specific function and global perceived effect), the effect of keeping the abdomen relaxed during Pilates was unclear, with confidence intervals ranging from roughly as good to mildly better than keeping the abdomen contracted. REGISTRATION: NCT05336500.