**5. Conclusions**

This study was the first to report on the varying effects of treadmill running, at different phases of RA, on the synovial membranes, articular cartilages, and bones of rat RA models. For RA patients as well, it may be possible for therapeutic exercise in the appropriate phases to increase bio-molecular suppression of arthritis through the suppression of inflammatory cytokine expression, and to consequently suppress joint destruction.

**Author Contributions:** Conceptualization, Y.F., S.S., H.I., and S.N.; Methodology, T.K.; Software, Y.F.; Validation, S.T. (Shinji Tsuchida), R.T., T.S., and K.I.; Formal analysis, Y.F. and S.T. (Shogo Toyama); Investigation, Y.F., S.S., Y.K., and K.K.; Resources, Y.A.; Data curation, Y. F., H.I., and Y.A.; Writing–original draft preparation, Y.F.; Writing–review and editing, all authors; Visualization, Y.F.; Supervision, T.K. and O.M.; Project administration, Y.A. and Y.M.; Funding acquisition, Y.F., S.T. (Shogo Toyama), S.N., and Y.A.

**Funding:** This work was supported by JSPS KAKENHI (grant numbers 17H02136, 18K10752, and 19K19914) and Grant of Japan Sports Medicine Foundation, 2018.

**Acknowledgments:** We would like to thank Editage (www.editage.com) for English language editing.

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