For over a century, technologists and scientists have actively sought the development of
exoskeletons and orthoses designed to augment human economy, strength, and endurance. While
there are still many challenges associated with exoskeletal and orthotic design that have yet to be
perfected, the advances in the field have been truly impressive. In this commentary, I first classify
exoskeletons and orthoses into devices that act in series and in parallel to a human limb, providing
a few examples within each category. This classification is then followed by a discussion of major
design challenges and future research directions critical to the field of exoskeletons and orthoses.