Reliability and Validity of Isometric Back Extensor Strength Measurements Using Hand-Held and Isokinetic Dynamometry in Sitting and Semi-Standing Positions

Introduction: The prone position is generally regarded as the standard posture for back extensor strength testing. However, some older adults may have difficulty assuming this position, making alternative approaches more clinically feasible. It remains unclear whether measurements obtained in the sitting and semi-standing positions demonstrate sufficient validity compared with those in the prone position. This study aimed to evaluate the reliability and validity of isometric back extensor strength measurements using hand-held dynamometry (HHD) in the sitting position and the Biodex system in the semi-standing position. The results were compared with measurements in the prone position.