Objective : In Europe, carbon dioxide therapy has been used for treating cardiac disease and skin problems for a long time. Previously, we demonstrated that transcutaneous carbon dioxide (CO₂) application facilitated dioxygen (O₂) dissociation from hemoglobin (Hb) in the human body. Additionally, we proved that transcutaneous CO₂ application to the lower limbs of rats increased the expression of peroxisome proliferator-activated receptor (PPAR) gamma coactivator-1α (PGC-1α), vascular endothelial growth factor (VEGF) and silent mating type information regulation 2 homologs 1 (SIRT1). It also increased the number of mitochondria, and changed IIB fiber to IIA fiber in similar manner to the change that occurs after exercise. The transcutaneous CO₂ application caused a similar effect to that of exercise training in skeletal muscle and indicated the possibility of improved endurance strength. However, the effect of transcutaneous CO₂ application on endurance exercise and the recovery of muscle fatigue has not been studied. Methods : In this study, we investigated the performance of endurance exercise in rats with/without transcutaneous CO₂ application and analyzed the muscle fiber changes, capillary density and mitochondrial DNA number of the skeletal muscles after training, using activity wheels. Results： Training with CO₂ application resulted in a higher percentage of TA muscle transformed to IIA and/or IID than training alone, suggesting that transcutaneous CO₂ application may increase the production of ATP, mitochondria number, and capillary density. Therefore, transcutaneous CO₂ application might lead to muscle damage recovery. Conclusion : We suggest that transcutaneous CO₂ application has a therapeutic potential for recovery of damaged muscle after excessive exercise and rehabilitation.