Balance Calculator: An Excel spreadsheet for automated computation of postural balance variables from IMU and force platform data

This Excel workbook automatically computes postural balance/sway variables from raw inertial measurement unit (IMU: accelerometer + gyroscope) and/or force platform data, without requiring any programming knowledge. The user pastes raw sensor data into the input sheets (Data_IMU and/or Data_Kistler); the workbook automatically removes the gravity/offset component, integrates acceleration/force to estimate center-of-mass (COM) displacement, computes the center of pressure (COP) from force platform moments, and derives the final outcome variables with their formulas and units shown alongside each result. Variables computed automatically: Center of pressure (COP): RMS, sway range, path length, mean velocity, 95% confidence ellipse area, approximate mean frequency Total power (Parseval approximation via variance) Jerk (RMS) PlayerLoad (normalized by sampling frequency) Peak angular velocity Center-of-mass (COM) displacement via double integration (IMU: least-squares linear drift correction; force platform: Zatsiorsky & King, 1998 method) The workbook currently supports up to 60,000 samples per repetition (e.g. 60 s at 1000 Hz, or 10 minutes at 100 Hz). It includes a 10-second example dataset (synthetic quiet-standing data) demonstrating that all formulas compute correctly, and an Instructions sheet explaining input cells, configuration parameters, and the known limitations of Excel-based computation (e.g. approximate entropy, sample entropy, the Lyapunov exponent and DFA analysis are not implemented, as they are not reliably computable with native spreadsheet formulas). All formulas were verified with LibreOffice recalculation (0 errors across ~2 million formula cells). The center-of-mass estimate obtained by double integration of IMU data is an approximation and has not been validated against a gold-standard reference (e.g. motion capture); it should be treated as an exploratory/secondary measure unless independently validated by the user.