INTRODUCTION: Stem cell transplantation is widely employed to treat various diseases, and adipose-derived mesenchymal stem cells (ASCs) are used for allogeneic xenotransplantation. However, muscle function post stem cell transplantation remains largely understudied. Therefore, we aimed to investigate the optimal conditions for the transplantation of ASC aggregates of gelatin hydrogel microparticles incorporating growth factors. We further aimed to establish a method for improving muscle function via ASC implantation combined with muscle loading through treadmill running. METHODS: Mouse ASCs suspended in various solutions were transplanted into the soleus muscles. The strength of each mouse was measured using a digital force gauge after a muscle load was applied using a treadmill. RESULTS: Platelet-rich growth factor-BB (PDGF-BB) effectively facilitated the expression of MYO-D in the ASCs. Moreover, the injection of cell aggregates rather than suspensions enhanced cell retention. Transplantation of ASC-aggregate gelatin hydrogel microparticles incorporating PDGF-BB in combination with muscle load using a treadmill enhanced mouse muscle function. CONCLUSIONS: ASC aggregates with growth factor transplantation likely enhance cell retention. Moreover, they likely improve muscle function and load. Thus, our findings provide new avenues for cell regeneration therapy in muscle rehabilitation.