title: Improving stand-to-sit maneuver for individuals with spinal cord injury.
abstract: BACKGROUND
  Users of neuroprostheses employing electrical stimulation (ES) generally complete the stand-to-sit (STS) maneuver with high knee angular velocities, increased upper limb support forces, and high peak impact forces at initial contact with the chair. Controlling the knee during STS descent is challenging in individuals with spinal cord injury (SCI) due to the decreasing joint moment available with increased knee angle in response to ES.
  
  
  METHODS
  The goal of this study was to investigate the effects of incorporating either (1) a coupling mechanism that coordinates hip and knee flexion or (2) a mechanism that damps knee motion to keep the knee angular velocity constant during the STS transition. The coupling and damping were achieved by hydraulic orthotic mechanisms. Two subjects with SCI were enrolled and each served as their own controls when characterizing the performance of each mechanism during STS as compared to stimulation alone. Outcome measures such as hip-knee angle, knee angular velocity, upper limb support force, and impact force were analyzed to determine the effectiveness of the two mechanisms in providing controlled STS.
  
  
  RESULTS
  The coordination between the hip and knee joints improved with each orthotic mechanism. The damping and hip-knee coupling mechanisms caused the hip and knee joint ratios of 1:1.1 and 1:0.99, respectively, which approached the 1:1 coordination ratio observed in nondisabled individuals during STS maneuver. The knee damping mechanism provided lower (p < 0.001) and a more constant knee angular velocity than the hip-knee coupling mechanism over the knee range of motion. Both the coupling and damping mechanisms were similarly effective at reducing upper limb support forces by 70 % (p < 0.001) and impact force by half (p ≤ 0.001) as compared to sitting down with stimulation alone.
  
  
  CONCLUSIONS
  Orthoses imposing simple kinematic constraints, such as 1:1 hip-knee coupling or knee damping, can normalize upper limb support forces, peak knee angular velocity, and peak impact force during the STS maneuvers.
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA. sarah.r.chang@case.edu.|Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA. sarah.r.chang@case.edu.
authors.forename: Sarah R
authors.identifier: http://orcid.org/0000-0002-2870-0055
authors.initials: SR
authors.lastname: Chang
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA.|Department of Mechanical Engineering and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Nandor
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA.
authors.forename: Rudi
authors.initials: R
authors.lastname: Kobetic
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Foglyano
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA.|Department of Mechanical Engineering and Aerospace Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA.
authors.forename: Roger D
authors.initials: RD
authors.lastname: Quinn
authors.affiliation: Department of Veterans Affairs, Advanced Platform Technology Center, Louis Stokes Cleveland VA Medical Center, 10701 East Blvd, 151AW/APT, Cleveland, OH, 44106, USA.|Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA.|Department of Orthopaedics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH, 44106, USA.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Triolo
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D009989:Orthotic Devices; D011187:Posture / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D016059:Range of Motion, Articular; D013119:Spinal Cord Injuries / Q000534:rehabilitation*
keywords: Biomechanics; Electrical stimulation; Hip-knee coupling; Hybrid neuroprosthesis; Knee damping; Orthotic knee mechanisms; Sitting impact force; Spinal cord injury; Stand-to-sit