SPORTS PERFORMANCE HUB
Y-Balance Pro (YBT)
Standardized Lower & Upper Quarter Symmetry Analysis
Enter limb length and reach values
to calculate Normalized Composite Score
The Science of Limb-Length Normalization
The Y-Balance Test (YBT) is a filtered version of the Star Excursion Balance Test. Because taller athletes naturally reach further, raw distances are scientifically meaningless. To rank an athlete fairly, raw scores must be divided by limb length to create a "Normalized" percentage.
Critical Risk Redlines
- Anterior Asymmetry: A difference of **>4 cm** between sides is a strong predictor of non-contact ACL injury.
- Composite Score: A score of **<94%** in high-school athletes is associated with an increased injury rate.
- Upper Quarter: A medial reach difference of **>4 cm** indicates shoulder instability.
Expert FAQs
How do I measure Lower Quarter limb length?
Measure from the **Anterior Superior Iliac Spine (ASIS)** to the center of the **Medial Malleolus** (inner ankle bone) while the patient is lying supine.
How do I measure Upper Quarter limb length?
Measure from the **C7 Spinous Process** to the tip of the **middle finger** with the arm abducted to 90 degrees.
Clinical Bibliography
- 1. Plisky PJ, et al. The reliability of an instrumented device for measuring components of the Star Excursion Balance Test. 2009.
- 2. Butler RJ, et al. Lower extremity stiffness and the Y-balance test in athletes. 2012.
Dr. Nikhil Mahajan, PT
CLINICAL RESOURCE