This is an effective tool for releasing and massaging the iliopsoas muscle (iliacus and psoas major), which greatly affects lower back pain and athlete performance. In Japan, there is still very little information available about this tool, even among trainers and massage therapists. It is sold overseas under the name "hip hook." The iliopsoas muscle, especially the iliacus, attaches to the pelvis (ilium), making it difficult to massage when straight. However, this tool applies a scooping vector, making it easier to contact the iliacus muscle. This YouTube video explains how to use it: https://www.youtube.com/watch?v=WhZiloNGYlQ Please refrain from purchasing if you are overly sensitive or a perfectionist, as individual differences exist. Also, as you will understand after using it, this tool is not meant to be used with excessive force, so we will not accept claims such as "the arm broke." (The arm should not break during normal use, as the force required would be too painful. Therefore, damage is likely due to misuse, such as stepping on it.) Search terms: Bodybuilding, personal trainer, personal gym, Pilates studio, Physical therapist, judo therapist, Physique, fitness bikini, bone-setting clinic, chiropractic.