A resource for axes misalignment, nonlinear error and normal gait data
I have put together an excel spreadsheet demonstrating axes misalignment, resulting non-linear errors, correction of these errors, and the derivation of normal gait joint angle data from the varied results presented in the literature. In 3DMA it is important to understand axes misalignment, its source, and its effects on joint angle data. As it is linked to the validity and reliability of joint angle data, poor reliability of current methods and the lack of normative gait joint angle data presented in the literature. The excel file also includes worked examples of post-hoc correction of nonlinear error in joint angle data via correction of respective proximal and distal segment’s axes mis-alignment. To provide a unique approach to 3D gait analysis that identifies and corrects static and dynamic components of axes misalignment. The excel file also demonstrates the non-linear correction of seemingly unrelated gait joint angle data presented in the literature to show, for the first time, normal gait joint angle data.
This will help explain concepts I have mentioned on BiomechL related to different marker sets, filtering joint angle data, limiting joint df’s and global optimisation (inverse kinematics approach) vs 6 df joints. There is a lot of information presented, and it will take time to work through and understand what is presented, but I believe they are valuable concepts and information for those working with 3DMA
I have shared a Google Drive folder containing two files. An Excel file "Normal gait data, axes misalignment and nonlinear error Jan 2017" (45MB) with the data and workings and a word file with the same name with brief explanation of what is in the excel file.
The folder "3DMA Normal Gait Data" is at:
or Excel file
or Word File