**3. Results**

The dataset for a squat includes tibio-femoral flexion angles from 0◦ to 90◦ . The discrepancy between the angles according to the different definitions increases with the tibio-femoral flexion angles. Based on the data for the Cardan XYZ-sequence, the angles for the five remaining Cardan sequences and the projected angles were calculated. In order to validate the conversion process, the Cardan sequences for the same dataset were evaluated directly from the general multibody software SIMPACK as reference. The

deviation of these results to the values from converting the XYZ data do not exceed 0.0001◦ (RMSE < (6.13 <sup>×</sup> <sup>10</sup>−<sup>5</sup> ) ◦ for all sequences and angles).
