Effects of breathing exercises combined with low back muscle exercises on lumbar function, pain, and quality of life after surgery for lumbar disc herniation: a three-arm randomized controlled trial

Patients undergoing surgery for lumbar disc herniation (LDH) may continue to experience pain, impaired lumbar function, disability, reduced health-related quality of life, and kinesiophobia. Because the diaphragm contributes to intra-abdominal pressure regulation and trunk stability, breathing exercises may complement low back muscle exercises. Evidence regarding breathing exercises after LDH surgery remains limited, and direct comparisons between abdominal breathing and inspiratory muscle training (IMT) are lacking. This study compared the additional effects of these two breathing interventions in patients undergoing minimally invasive lumbar discectomy. In this three-arm randomized controlled trial, 87 patients scheduled for minimally invasive lumbar discectomy were randomly assigned in a 1:1:1 ratio to the low back muscle exercise alone group (control group, designated CG), abdominal breathing plus low back muscle exercise group (designated AG), or inspiratory muscle training plus low back muscle exercise group (designated IG), with 29 participants per group. All three groups received routine postoperative health education and the same low back muscle exercise program. AG and IG additionally performed abdominal breathing and inspiratory muscle training, respectively, for 12 weeks. Outcomes were assessed at baseline and after the 12-week intervention. The primary outcome was lumbar function assessed using the traditional Japanese Orthopaedic Association (JOA) score for low back pain (maximum score, 29 points). Secondary outcomes included the Oswestry Disability Index (ODI), Numeric Rating Scale (NRS) for pain intensity, 36-Item Short Form Health Survey (SF-36), and Tampa Scale for Kinesiophobia (TSK). Of the 87 randomized participants, 83 completed the 12-week assessment and were included in the complete-case analysis. All three groups showed significant improvements in lumbar function, disability, pain, and kinesiophobia; all eight SF-36 domains improved in the AG and IG groups, whereas seven of the eight domains improved in the CG group. At 12 weeks, the IG group had better JOA, ODI, TSK, and most SF-36 outcomes than the AG and CG groups (all P < 0.05). Both breathing exercise groups had lower NRS scores than the CG group ( P < 0.001 for IG and P = 0.004 for AG), with no significant difference between them ( P = 0.820). No breathing exercise-related adverse events were reported. Both breathing interventions improved postoperative recovery outcomes in patients with lumbar disc herniation. Inspiratory muscle training was more effective than abdominal breathing in improving lumbar function and most health-related quality-of-life domains and in reducing disability and kinesiophobia. This trial was prospectively registered on April 12, 2024, before enrollment of the first participant on April 15, 2024 (ChiCTR2400083000).