**5. Conclusions**

This study investigated the changes in the kinematic and kinetic characteristics of lunge footwork during the fatiguing process. To the best of our knowledge, this study was the first to subdivide the fatiguing process and analyze the changes among di fferent sub-stages. It was also the first study to use one-dimensional statistical parametric mapping (SPM (1D)) to analyze the e ffect of fatigue on the lunge footwork in badminton. Statistically significant di fferences were found in both the discrete and waveform data. Moreover, these di fferences were shown not only between pre- and post-fatigue, but also among other sub-stages.

Overall, the results presented in this study confirm that period IV of the stance phase is more sensitive to fatigue than the other periods. In addition, the training program should focus on muscular strengthening of the knee extensor, particularly in period IV. It is also important to improve the strength of hip extensors. Furthermore, although the results show consistent changes between the discrete and waveform data, findings from this study highlight that results of SPM (1D) are more useful for the

assessment of weak areas of the body and periods of motion. This information may contribute to the future design and development of training plans and to the monitoring of training.

**Author Contributions:** Y.D. designed, carried out the experiments, analyzed the data and wrote the paper, Y.F. designed the experiments, reviewed and revised the paper. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was supported by the National Natural Science Foundation of China (NSFC), gran<sup>t</sup> number 11421202.

**Acknowledgments:** We thank Changhao Jiang from Capital University of Physical Education and Sports and Huijuan Tian from Tianjin Polytechnic University for giving suggestions for the analysis. We thank all the participants in this study.

**Conflicts of Interest:** The authors have no conflict of interest concerning this manuscript.
