Functional electromechanical dynamometer is a new, reliable, and safe tool to assess trunk muscle strength in young adults with non-specific chronic low back pain

Chronic low back pain (CLBP) is a leading cause of disability worldwide. Trunk muscle weakness is linked to the onset and severity of CLBP. While isokinetic dynamometers are reliable for assessing trunk flexors, extensors, and rotators, the reliability and safety of Functional Electromechanical Dynamometers (FEMD) remain insufficiently studied. Therefore, this study aimed to determine the reliability and safety of trunk strength assessment using FEMD in adults with non-specific CLBP (NSCLBP). Twenty-eight participants with NSCLBP attended three sessions: familiarisation and two assessments (48-72 hours apart). Trunk flexors, extensors, and rotators were assessed using isokinetic and isometric modes with a FEMD. Reliability was analysed using intraclass correlation coefficients (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland-Altman plots. Reliability was good to excellent across all trunk muscle groups: flexors (ICC = 0.87-0.92), extensors (ICC = 0.87-0.90), right rotators (ICC = 0.91-0.96), and left rotators (ICC = 0.86-0.96). Mean SEM ranged from 0.88 to 12.63 kg and CV from 6.56 to 15.63%. Three participants reported mild transient discomfort immediately after testing, with no pain reported at 24 hours. These findings indicate that FEMD-based assessment of trunk strength is reliable and safe for patients with NSCLBP, supporting its application in clinical and research settings to monitor rehabilitation.