Comparison of manual and semi-automated algorithm for measuring architectural features during different isometric knee extension intensities: a reliability and comparative study in novice raters.
Micheal J Luera, JoCarol E Shields, Emma Bozarth and 6 others
PMID 40248069WHAT IT FOUND
Novice raters measuring knee muscle architecture via ultrasound achieved high reliability using a semi-automated algorithm but poor reliability with manual methods.
The algorithm reduced analysis time to under 90 seconds per image and maintained consistency across different contraction intensities.
Key findings
01Semi-automated analysis yielded good to excellent intra-rater reliability for fascicle length, pennation angle, and muscle thickness, whereas manual analysis by novices showed poor to moderate reliability.
02The semi-automated algorithm required approximately 88 seconds per image, compared to an estimated 10 minutes for manual extraction in a separate reference study.
03Semi-automated measures showed systematic bias compared to manual measures, with fascicle lengths appearing longer and pennation angles smaller, though muscle thickness values were comparable.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study used only healthy, highly trained individuals, so reliability in patients with pathology or injury is unknown. Raters were novices, which likely worsened manual reliability compared to expert use, though this reflects real-world lab settings. The study did not validate the algorithm against a gold standard or expert raters, so it is unclear which method is more accurate. Sample size was small (N=15).
Declared interests
Funding was provided by the Clinical and Translational Science Award (CTSA) program via National Center for Research Resources grants.
The easy way to misread this
Do not assume semi-automated measurements are identical to manual ones. The algorithm produced fascicle lengths 4.0 cm longer and pennation angles 2.99° different than manual tracing, so you cannot switch methods mid-study without recalibrating your norms.