Objective: This study aimed to evaluate lumbar lordosis during sit-to-stand (STS) and stand-to-sit (SIT) in individuals with and without chronic nonspecific low back pain (CNLBP). The second objective was to investigate sex-related differences in lumbar lordosis.

Methods: Twenty-six patients with CNLBP and 26 controls were recruited. Controls were matched with cases using a frequency matching method. Reflective markers were placed over the spinous process of T₁₂, L₃, S₂, and the anterior and posterior superior iliac spines. The participants were instructed to stand up at a self-selected pace and maintain their normal upright standing posture for 3 seconds, and then sit down. Kinematic data were recorded at a sampling frequency of 100 Hz using a motion capture system. Lumbar lordosis angle was calculated from the intersection between the line joining T₁₂ and L₃, and the line joining L₃ to S₂.

Results: Lumbar lordosis was decreased in patients with CNLBP during STS and SIT compared with the asymptomatic group (mean difference = 2.68°-9.32°; P ≤ .005). Furthermore, no differences were seen in lumbar lordosis at starting position between CNLBP and asymptomatic groups during STS and SIT (mean difference = 2.68°-3.75°; P ≥ .099). Interestingly, the magnitude of the effect size suggested that the difference in lumbar lordosis values between female and male participants was relatively large (Cohen's d = -1.81 to 0.20).

Conclusion: Decreased lumbar lordosis in patients with CNLBP during STS and SIT could be considered as an important point during rehabilitation. Moreover, the present study showed that there is a sex-related difference among women and men in lumbar lordosis during STS and SIT tasks.

Author keywords: Movement; Kinesiology; Lumbar Vertebrae; Low Back Pain; Lordosis; Sex

Author affiliations: MP, JS, HM, SHF: Department of Physiotherapy, School of Rehabilitation Sciences, Iran University of Medical Sciences, Tehran, Tehran, Iran; IET, RB: Neuromuscular Rehabilitation Research Center, Department of Physiotherapy, Semnan University of Medical Sciences, Semnan, Semnan, Iran; MT: Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Tehran, Iran.

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