Abstract: The subject invention pertains to a pneumatic, hydraulic, or otherwise inflatable or pressurized artificial muscle. Also provided are methods for making, controlling, and using such a muscle useful for prostheses, movement aids, or wearable robots to assist the movement of impaired subjects or to improve the function of healthy subjects. Muscles can be made by densely winding tension wires around pressurized expandable tubes having one or more specific geometric shapes removed from the tube cross section. The curve of output characteristics such as output force vs. contraction ratio can be adjustable by changing parameters of the sectional view of the tube. The appropriate shape of tube and related output characteristics can be selected according to application area or body part to be assisted to achieve the most flexible and optimal design for one or more muscle groups.