This literature review of exoskeleton design provides a brief history of exoskeleton development, discusses current research of exoskeletons with respect to the innate human-machine interface, and the incorporation of exoskeletons for ergonomic intervention, and offers a review of needed future work. Development of assistive exoskeletons began in the 1960's but older designs lacked design for human factors and ergonomics and had low power energy density and power to weight ratios. Advancements in technology have spurred a broad spectrum of research aimed at enhancing human performance and assisting in rehabilitation. The review underwent a holistic and extensive search and provides a reflective snapshot of the state of the art in exoskeleton design as it pertains to the incorporation of exoskeletons for ergonomic intervention. Some of the remaining challenges include improving the energy density of exoskeleton power supplies, improving the power to weight ratio of actuation devices, improving the mechanical human-machine interface, and dealing with variability between users.