This study aimed to investigate the differences in exercise load due to variations in lower limb weight during stair ascent and descent. The study involved 10 healthy adult men and women without respiratory or circulatory disease (five men and five women). Using a respiratory gas analysis device, the participants performed stair climbing under three conditions: 1) full weight-bearing, 2) half (partial) weight-bearing, and 3) non-weight-bearing. The maximum oxygen uptake during stair climbing was defined as the peak oxygen uptake. Additionally, the time required for ascent and descent was measured using a stopwatch, and heart rate and perceived fatigue at the end were assessed using the Borg scale. Peak oxygen uptake and Borg scale scores significantly increased during ascent and descent under the non-weight-bearing condition compared to those under the full weight-bearing and half-weight-bearing conditions. The required time was significantly extended under the half-weight-bearing and non-weight-bearing conditions compared to under the full-weight-bearing condition. Therefore, when stair ascent and descent are necessary during a period requiring the use of crutches, it is considered desirable to perform the task only after at least half-weight-bearing condition or more is permitted, as this approach results in a considerable reduction in load.