Validity and reliability of hand-held dynamometry for abdominal flexion muscular assessment

Context: Abdominal musculature underpins core stability, which can allow for optimal performance in many activities of daily living (eg, walking and rising from a chair). Therefore, assessment of the abdominal muscles poses as an important consideration for clinicians in order to identify people at risk of injury or functional decline. Objective: This study aimed to build on the limited amount of knowledge surrounding abdominal muscle strength assessments by investigating the validity and reliability of handheld dynamometry (HHD) for the assessment of isometric abdominal flexion strength. Study Design and Participants: Comparative analysis for validity and test-retest reliability was employed on a cohort of apparently healthy individuals. HHD was compared with the criterion, isokinetic dynamometry, through an isometric contraction of trunk flexion on both instruments. Hand-held dynamometry assessments only were performed on a subsequent day for reliability analysis. The peak values for all assessments were recorded. Results: A total of 35 participants were recruited from the University of South Australia and the general public. Comparative analysis between the HHD and isokinetic dynamometer showed good agreement (intraclass correlation coefficients = .82), with the Bland-Altman plots confirming no proportional bias. Reliability analysis for the HHD reported good consistency (intraclass correlation coefficients = .87). Conclusion: HHD together with the participant setup (supine, trunk flexed, and supported at 25° with the legs horizontal and remaining unfixed) is a valid and reliable tool to assess isometric abdominal flexion strength.