biodex 950-440 - Page 127

Balance System SD (with v4.X software) 127
Direction Efficiency %:
𝐷𝑖𝑟𝑒𝑐𝑡𝑖𝑜𝑛 !𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦% =
𝑆𝑡𝑟𝑎𝑖𝑔ℎ𝑡!𝐿𝑖𝑛𝑒 ! 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒!𝑥!2
𝐴𝑐𝑡𝑢𝑎𝑙!𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 !𝑡𝑜! 𝑎𝑛𝑑!𝑓𝑟𝑜𝑚
!𝑋!100
Sway Velocity Index: A value based on Velocity (mm/s), which is the total distance the COP
traveled in the medial lateral path/time.
It is referred to an index because each patient’s score is first normalized by a natural log
function (Ln) of the medial-lateral center of pressure velocity (CPV
ML
), divided by the patient’s
body height (BH). To make the scoring similar to other types of sway indexes calculated by the
system software, it is multiplied by 1000.
𝑆𝑤𝑎𝑦!𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦!𝐼𝑛𝑑𝑒𝑥 =
Ln( 𝐶𝑃𝑉
!"
)
𝐵𝐻
!𝑋!1000
Where:
CPV
ML
= Mean medial-lateral center of pressure velocity (mm/s).
BH=Patient’s body height in cm.
Velocity (mm/s) is the total distance the COP traveled in the medial lateral path/time.
𝑆𝑉𝐼!𝑎𝑠!𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑𝑖𝑧𝑒𝑑!𝑆𝑐𝑜𝑟𝑒 = 𝑍!𝑆𝑐𝑜𝑟𝑒 =
SVI −!!
!"# !!"
𝜎
!"# !!"
!
Where:
SVI= Sway Velocity Index from patient.
!!
!"# !!"
= Mean Sway Velocity Index for respective Age Group.
𝜎
!"# !!"
= Standard Deviation Sway Velocity Index for respective Age Group.
This value is compared to normative data as a Z score. A Z score indicates how many standard
deviations SVI is from the mean.
Platform setting: Indicates the stability (stiffness) of the foot platform. When locked, the
platform is fully stable (static). A setting of 1 is the most stable released setting. A setting of 12
is the least stable foot platform setting. Stability settings of 1 through 12 allow the platform a
full 20 degrees of deflection from level in any direction. For patient centering prior to testing,
the platform deflection is limited to less than five degrees.