Here we discuss exoskeletons that act in parallel with the
human joint(s) for torque and work augmentation. Many
parallel-limb exoskeletons have been developed to augment
joint torque and work [33-58]. In distinction to the
load-carrying exoskeletons mentioned in the last section,
this type of exoskeletal and orthotic device does not transfer
substantial load to the ground, but simply augments
joint torque and work. This type of leg exoskeleton could
improve walking and running metabolic economy, or
might be used to reduce joint pain or increase joint
strength in paralyzed or weak joints.