An Objective Assessment for Plank Performance in Active Adults With and Without Low Back Pain: A Reliability and Comparison Study.

Authors

Matt Turner, Michael O'Dwyer, Cassie Schumacher, Kelli Brizzolara, Amanda Arnold, Sharon Wang-Price

Published in

International journal of sports physical therapy. Volume 21. Issue 10. Pages 984-995. Epub Oct 01, 2026.

Abstract

Timed plank tests often are used to assess trunk performance in patients with low back pain (LBP). However, a timed test does not assess the quality of movement or the amount of compensatory movement patterns that may reflect altered motor control. Currently, an objective method to quantify trunk deviation during the plank is lacking.
To determine the inter-rater and intra-rater reliability of the maximum amount of trunk deviation (MOTD), measured using a digital inclinometer during forward- and side-plank testing, and to compare MOTDs and time to failure (TTF) between active adults with and without LBP.
Reliability and comparison study.
Thirty-four active young adults (17 without LBP, 17 with LBP) completed two sessions of the forward and side-plank tests separated by a 10-minutes rest period. Both tests were elbow-supported and performed with extended legs. A digital inclinometer was placed at L4-L5 during the forward-plank test and above iliac crest during the side-plank test. Each trial was video-recorded from a sagittal-plane view during forward-plank testing and a frontal-plane view during side-plank testing. Two investigators performed independent testing sessions to establish the inter-rater reliability. For the intra-rater reliability, one investigator extracted data by viewing the recordings of the live exam at least two weeks after the initial assessment. Intraclass correlation coefficients (ICCs) were calculated to determine reliability, and independent t-tests were used to compare MOTD and TTF between groups.
The results showed good intra-rater reliability (ICC = .81-.85), and moderate inter-rater reliability (ICC = .61-.66) for both groups, with the LBP group having lower ICCs. A significant between-group difference was observed for side-plank MOTD (p = 0.005), with the LBP group demonstrating smaller MOTDs. No differences were observed in TTF.
The study supports the use of a digital inclinometer as a reliable tool for measuring trunk deviation during planks in active young adults. In addition, individuals with LBP may perform a side plank differently than those without LBP.
2b.

PMID:
42893319
Bibliographic data and abstract were imported from PubMed on 18 Oct 2026.

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