Described herein is an arm supporting exoskeleton, comprising an arm link mechanism. The arm link mechanism comprises a proximal link, a distal link, an arm coupler, and a variable force generator. The distal link is rotatable relative to the proximal link. The arm coupler is adapted to couple an upper arm of a person to the distal link. The variable force generator comprises a first spring and a second spring, configured to create a torque between the proximal link and the distal link. In the first force mode, the variable force generator exhibits a first stiffness rate defined by the first spring that supports the upper arm of the person against gravity forces and. In the second force mode, the variable force generator exhibits a second stiffness rate defined by the first spring and the second spring that supports the upper arm of the person against the gravity forces.