History:Objectives: Little is known regarding the associations between Borg's rating of perceived exertion (RPE), cardiopulmonary responses, and carrying bags while level walking. We investigated the changes in RPE and cardiopulmonary responses, including energy cost (EC), oxygen consumption (VdotO₂), and heart rate (HR), when walking with a bag.Methods: This randomized crossover study included 10 healthy adults (aged 21-22 years). Four days of experiments were performed at intervals of 1-2 weeks. The participants walked on a level treadmill while carrying a bag with a strap weighting 5 kg, placed diagonally on their shoulders (DS), vertically on their shoulders (VS), vertically in one hand (VH), and on their backs using both shoulders (BS) for 20 min. Walking speed was stable among all experiments, and was set to the participants' preferred speed.Results: No significant differences between bag carrying methods regarding EC, VdotO₂, and %HRreserve (based on HR) were observed, whereas RPE respiratory (RPE-resp) and RPE leg muscle (RPE-leg) scores varied based on bag carrying method used. RPE-resp score was significantly lower for DS and BS than VH (both p < 0.0083); however, no significant difference was observed when each RPE-leg score was compared. Conclusions:We found that RPE-resp score varied, whereas no changes in EC, VdotO₂, and HR were observed in healthy adults while walking with different bag carrying methods. Additionally, of all bag carrying methods assessed, the highest RPE-resp score was observed when individuals carried a bag with one-hand at their side.