Reliability of an Observational Biomechanical Analysis Tool in Adolescent Baseball Pitchers.
Steven F DeFroda, Dai Sugimoto, Steven J Staffa and 4 others
PMID 34909257WHAT IT FOUND
A 2D video tool for adolescent baseball pitchers gave consistent total scores among trained sports raters, but some individual mechanics items were less consistent.
It does not yet show injury risk or replace 3D motion analysis.
Key findings
01For total scores, the ACES tool showed excellent agreement when each rater scored the videos twice two weeks apart and when the three raters' scores were compared.
02Agreement on individual mechanics items was less consistent, with absolute inter-rater agreement from 50% to 100% and intra-rater agreement from 70% to 100%.
03The most frequently rated errors were front side position, stride length, and lead hip position during the windup.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only 20 pitchers were studied, all asymptomatic male adolescents aged 12 to 18 years with at least two years of pitching experience. The study analyzed one best-effort pitch per pitcher, so it did not assess mechanics across many pitches or with fatigue. ACES reliability was tested against the raters' own repeated scores, not against 3D motion analysis or injury outcomes. Some ACES items required several conditions to count as correct, which may make grading harder. Raters were trained sports medicine providers, not coaches or untrained laypeople, so reliability may not extend to the intended non-clinical users. The two testing sites used different camera frame rates and different throwing targets, a catcher at one site and a strike zone target at the other.
Declared interests
The authors reported no applicable financial disclosures and no conflicts of interest.
The easy way to misread this
Do not treat a high ACES error score as evidence that a pitcher is injured or likely to be injured. This study only showed that trained raters agreed when scoring the same video, not that the scored errors cause injury or replace 3D motion analysis.