The Static Balance Test is a diagnostic tool of the GABLE platform. It was developed to track changes in the standing balance of the patient. It is based on the classic measurement known as Stabilometry or Posturography. It evaluates every sway while the patient is standing on the Nintendo Balance Board.

- Log in to the GABLE client, select the patient and run the Static Balance Test.
- Follow the screen instruction for connecting the Balance Board.
- After the calibration of the balance board, step on the board and stay still trying not to move for 10 seconds and look at the red dot.

A patient is given three trials, each trial lasts for ten seconds. During each trial the coordinates of Centre of Pressure (COP) are sampled 220 times.

After completion of 3 trials, test results are shown on screen. One or several trials that were incorrect could be dismissed and repeated once more

Test results page includes charts of 95 % confidence ellipse of COP displacement for each trial and following parameters:

- DOT - displacement of sway total or COP path length;
- Area - the area of the 95 % confidence ellipse;
- RMS anterior – posterior (a-p), RPS media- lateral (m-l) -root mean square of displacement in anterior-posterior and medial-lateral directions;
- AdCP a-p, AdCP m-l -the distance between the maximum and minimum centre of pressure displacement;
- MV a-p, MV m-l - mean velocity in anterior-posterior and medial-lateral direction;
- TMV - total mean velocity.

Those parameters are widely used in clinical stabilometry to evaluate stance stability of the patient in both directions – anterior- postrerior (forward – backwards) and medio-lateral (left-right) and could be interpreted by trained physician or therapist.

For simplification, most important parameter of posturography is a COP path length displacements, a total displacement of centre of pressure during 10 sec.

The results of posturography testing have been verified by means of exporting the data and calculations of all the parameters using external Matlab software. Details of the verification process are described in the public deliverable D.2.1 of the GABLE project “Implemented Games” in the section “Implementation of posturography data analysis in the Static Balance Test application”. Below is a short summary of the verification process.

The Wii Balance Board (WBB) consists of four piezoelectric sensors, each one at the bottom of each corner: the Top-Left Sensor (TLS), the Top-Right Sensor (TRS), the Bottom-Left Sensor (BLS) and the Bottom-Right Sensor (BRS). These sensors are crucial for the operation of the WBB, they convert the amount of physical pressure to a digitally represented number. Each sensor’s value is needed to calculate the Centre of Pressure1,2 (CP) of the person standing on the WBB at a certain point in time. CP represents the offset point (mm) from the centre of the WBB. The centre of the WBB is at CP (0,0). CP is calculated by using the following formulas:

- Left Input (LEFT) = TLS + BLS
- Right Input (RIGHT) = TRS + BRS
- Top Input (TOP) = TLS + TRS
- Bottom Input (BOTTOM) = BLS + BRS
- Horizontal Input (HORIZONTAL) = LEFT + RIGHT
- Vertical Input (VERTICAL) = TOP + BOTTOM
- CP medial-lateral (CPml) = (Horizontal Sensors Distance (mm) * (RIGHT - LEFT)) / (2 * HORIZONTAL)
- CP anterior-posterior (CPap) = Vertical Sensors Distance (mm) * (TOP - BOTTOM)) / (2 * VERTICAL)
- CP = (CPml, CPap)

The formulas that are used to calculate the results, are from the papers “Validation of the Balance Board™ for Clinical Evaluation of Balance Through Different Conditions” and “Revision of posturography based on force plate for balance evaluation”.

The results obtained from the Matlab code and the C++ implementation code have been verified and matching.