**5. Conclusions**

These initial results show that, based on the original frames, the IMU and the corresponding mathematical methods can e ffectively distinguish the motion accuracy of all eight motions of Baduanjin between novice and senior students. Furthermore, the IMU can identify the di fferences between the novice and senior students on the specific skeleton points of the eight motions of Baduanjin. The results regarding key-frames on clustering were highly correlated with the results of the original frames, which means, to a certain extent, that key-frames can replace the original frame to decrease the data storage space and processing time.

**Author Contributions:** Conceptualization, H.L, S.K., and H.J.Y.; Methodology, H.L, S.K., and H.J.Y.; Validation, H.L, S.K., and H.J.Y.; Data curation, H.L. and H.J.Y.; Writing—original draft preparation, H.L.; Writing—review and editing, S.K. and H.J.Y.; Supervision, S.K. and H.J.Y.; Funding acquisition, H.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Neijiang Normal University, Grant no: YLZY201912-1/-15, and the University of Malaya Geran Penyelidikan Fakulti, Grant no: GPF041A-2019.

**Acknowledgments:** We thank all participants and Neijiang Normal University for providing the facilities for the experiment.

**Conflicts of Interest:** The authors declare no conflict of interest.
