〔目的〕膝前十字靱帯（ACL）再建術後1年のHop test回復状況を調査し，回復基準に至りにくいHop testを明らかにすること．〔対象と方法〕ACL再建術を施行した218症例を対象とし，術後1年のVertical Hop（VH），Single Leg Hop（SLH），Triple Hop（TH）が健患比90％以上に回復した割合と3種のHop test全項目が健患比90％以上に回復した割合を調査した．〔結果〕Hop testの回復割合はVH 67.9％，SLH 78.4％，TH 78.9％であり，VHの回復割合が最も低かった．Hop test全項目が健患比90％以上に回復した割合は59.2％であった．〔結語〕約4割の症例においてHop testが健患比90％未満であり，特にVHの回復率が低かった．

To prevent back pain during load lifting, assist suits have been developed to reduce physical load by assisting human motion. There are two methods of lifting heavy objects: the stoop method and the squat method. Assistive suits to facilitate the squat method, which reduces the burden on the lower back, have not yet been put to practical use. Therefore, there is a need to develop assistive suits that are lightweight and do not require power. In this study, we developed a short leg orthosis using a leaf spring made of carbon fiber reinforced plastic (CFRP), and conducted lifting and unloading experiments of heavy objects while wearing the orthosis. We then investigated the work support effects of wearing the orthosis based on measurements of lower limb joint power using a three-dimensional motion analysis system and surface electromyography measurements. The results showed that joint angles and power at the ankle and knee joints during lifting was reduced, and joint angles at the ankle and knee joints and power at the knee joint during unloading was reduced by using the orthosis. In both lifting up and unloading, muscle use of the rectus femoris and gastrocnemius muscles decreased, while spinal muscles showed an increasing trend. In addition, muscle synergy analysis revealed two muscle synergies in both lifting up and unloading, indicating that wearing the orthosis reduced lower limb strain during lifting up, and reduced lower back and lower limb strain during unloading and standing up.