BACKGROUND: Elderly people experience a heavy physical burden due to deteriorated respiratory function owing to prolonged sitting defecation posture due to constipation. In recent years, to reduce the physical burden of defecation, arm support handrails, which support the arms in a forward-leaning posture, have become more widely available; however, their impact on breathing comfort has not yet been verified. This study's purpose was to compare the respiratory function of elderly people in traditional defecation postures and the arm-supported, forward-leaning position using the handrail, and thus verify whether the supported position has a positive effect. METHODS: The trunk leaning angle, respiratory function, thoracic range of motion, and subjective comfort of 57 healthy elderly people were measured and compared in each of the three sitting defecation postures: upright, forward-leaning, and arm-supported forward-leaning. RESULTS: The arm-supported, forward-leaning position involves a trunk leaning angle of 61.84° ± 7.47°, and vital capacity of the respiratory function, thoracic range of motion (axillary region), and subjective comfort in this position are all shown to be significantly higher than those in the other postures. CONCLUSION: The arm-supported, forward-leaning defecation posture provides a high degree of freedom in the abdomen due to proper forward-leaning, while the upper limb support improves the mobility of the upper thorax, thus ensuring high lung volume. In addition, the increased stability provides a comfortable feeling. Therefore, we conclude that the arm-supported, forward-leaning position is more effective for defecation than the general defecation position.