title: A powered prosthetic ankle joint for walking and running.
abstract: BACKGROUND
  Current prosthetic ankle joints are designed either for walking or for running. In order to mimic the capabilities of an able-bodied, a powered prosthetic ankle for walking and running was designed. A powered system has the potential to reduce the limitations in range of motion and positive work output of passive walking and running feet.
  
  
  METHODS
  To perform the experiments a controller capable of transitions between standing, walking, and running with speed adaptations was developed. In the first case study the system was mounted on an ankle bypass in parallel with the foot of a non-amputee subject. By this method the functionality of hardware and controller was proven.
  
  
  RESULTS
  The Walk-Run ankle was capable of mimicking desired torque and angle trajectories in walking and running up to 2.6 m/s. At 4 m/s running, ankle angle could be matched while ankle torque could not. Limited ankle output power resulting from a suboptimal spring stiffness value was identified as a main reason.
  
  
  CONCLUSIONS
  Further studies have to show to what extent the findings can be transferred to amputees.
authors.affiliation: Lauflabor Locomotion Laboratory, Institute of Sports Science, TU Darmstadt, Magdalenenstraße 27, 64289, Darmstadt, Germany. grimmer@sport.tu-darmstadt.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Grimmer
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Holgate
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Holgate
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Boehler
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Ward
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Hollander
authors.affiliation: Springactive, Inc., 2414 W. 12th Street Suite 4, Tempe, AZ, 85281, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Sugar
authors.affiliation: Lauflabor Locomotion Laboratory, Institute of Sports Science, TU Darmstadt, Magdalenenstraße 27, 64289, Darmstadt, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Seyfarth
mesh_terms: D000054:Acceleration; D000674:Amputees; D000842:Ankle / Q000502:physiology; D000843:Ankle Joint / Q000502:physiology*; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005684:Gait; D006801:Humans; D008297:Male; D011474:Prosthesis Design / Q000379:methods*; D016059:Range of Motion, Articular; D012420:Running / Q000502:physiology*; D019415:Torque; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Ankle; Joint; Power; Prosthesis; Running; Walking; Work