The Test-Retest Reliability and Minimum Detectable Change of a Dynamometric Device used to Quantify Lifting Strength

Nova Southeastern University, Davie, Florida, USA

Objective. Determine the test-retest reliability and minimum detectable change (MDC) of a dynamometric device (DYN) used to quantify isometric lifting strength. Background. The ability to perform lifting maneuvers from varying heights is a basic activity of daily living. Lifting assessments are used to quantify strength, profile injury risk, and determine work capacity. Vertical lifting strength from below the waist may be quantified using free-weights, lift- boxes, and dynamometry. While DYNs are most efficient for testing time and portability (eliminate need to use weights), a paucity of research exists to determine their reproducibility and error-based clinimetric properties. Methods. Fifty healthy participants (mean age 25-years) were recruited via convenience sampling. Following consent, participants underwent a brief warm-up followed by the lifting assessment. Participants stood on a platform; knees and hips slightly flexed, maintained a lumbar spine lordosis and grasped the DYN handle at knee level. Upon command, participants lifted in a vertical direction with maximum effort. Four repetitions were completed 1-minute apart and repeated 48-hours later. Results. Intersession test-retest reliability was excellent, with an intraclass correlation coefficient (3,1) = .969. The MDC (90% confidence interval) was 18 kilograms (kg). Conclusion. The DYN used in this study possessed excellent reliability during the initial phase of lifting where physical demands are the greatest. The MDC90 indicates that changes of 18kg or greater are needed to exceed the threshold of error. A limitation of this study is the use of an isometric task, which is only one position of a dynamic functional lifting task.