Dynamometry for the assessment of trunk muscle strength in postpartum women with pregnancy-related posterior pelvic girdle pain: A reliability study

Abstract

Objectives: To investigate the inter and intra-rater reliability of maximum isometric trunk muscular strength in postpartum women with pregnancy-related posterior pelvic girdle pain using a handheld dynamometer. Methods: Thirty women (30.13 +/- 3.67 years) with pregnancy-related posterior pelvic girdle pain (PPGP) had their trunk muscular strength assessed using a handheld dynamometer. Inter-rater reliability was estimated for measurements of two separate raters on the first day of the investigation. The tests were repeated with the first rater seven days later to determine the intra-rater reliability. A digital handheld dynamometer was used for testing, and a metal bar was used to secure it to a table. Participants were instructed to use maximal force to push the dynamometer in various trunk flexion, extension, lateral flexion, and rotational orientations. Each trial was repeated three times and averaged to obtain the representative assessment data. Analysis of variance, interclass correlation, absolute agreement, and standard error of measurements were used to evaluate the repeatability of measurements. Results: Excellent inter and intra-rater reliability were demonstrated. The inter-rater reliability, computed with intraclass correlation coefficient (ICC), ranged from 0.979 to 0.992, and intra-rater reliability (ICC) ranged from 0.966 to 0.987. The standard error of measurement ranged from 0.35 to 1.26 for the different tests. Additionally, the dynamometer values in women with PPGP might be reported using just one trial after an instruction. Conclusion: The maximum isometric trunk muscular strength is reliable, and a quantitative assessment of the trunk strength in women with postpartum pregnancy-related posterior pelvic girdle pain and could be used to monitor the changes in postural stability between sessions.