Recently, robots are expected to support our daily lives in real environments. There are a lot of disturbances during physical interaction, e.g., shaking hands, hugging human and holding various objects. Because of the unexpected noises, it is difficult for robots to act in such complicated situations flexibly. On the other hand, thanks to the flexibility of body structure, human can cope with various disturbances. It is suggested that the property is realized by changing the passive dynamics depending on the situation and task. There are two important mechanisms for changing the passive dynamics, one is a high degree of freedom, i.e., redundancy of joints, and the other is a multi-articular muscle, i.e., redundancy of actuators. Thanks to these redundancies, various movements and power adjustments can be realized. In this research, a human-like upper body musculoskeletal robot with redundant joints and actuators is developed. The robot can change its passive dynamics just by changing the connection of air actuators, i.e., changing the constraint of joints. This paper presents the structure of the robot and some open-loop motions by it. The response characteristics of the arm with differently connected actuators are also shown.