title: Effect of body weight support variation on muscle activities during robot assisted gait: a dynamic simulation study.
abstract: OBJECTIVE
  While body weight support (BWS) intonation is vital during conventional gait training of neurologically challenged subjects, it is important to evaluate its effect during robot assisted gait training. In the present research we have studied the effect of BWS intonation on muscle activities during robotic gait training using dynamic simulations.
  
  
  METHODS
  Two dimensional (2-D) musculoskeletal model of human gait was developed conjointly with another 2-D model of a robotic orthosis capable of actuating hip, knee and ankle joints simultaneously. The musculoskeletal model consists of eight major muscle groups namely; soleus (SOL), gastrocnemius (GAS), tibialis anterior (TA), hamstrings (HAM), vasti (VAS), gluteus maximus (GLU), uniarticular hip flexors (iliopsoas, IP), and Rectus Femoris (RF). BWS was provided at levels of 0, 20, 40 and 60% during the simulations. In order to obtain a feasible set of muscle activities during subsequent gait cycles, an inverse dynamics algorithm along with a quadratic minimization algorithm was implemented.
  
  
  RESULTS
  The dynamic parameters of the robot assisted human gait such as joint angle trajectories, ground contact force (GCF), human limb joint torques and robot induced torques at different levels of BWS were derived. The patterns of muscle activities at variable BWS were derived and analysed. For most part of the gait cycle (GC) the muscle activation patterns are quite similar for all levels of BWS as is apparent from the mean of muscle activities for the complete GC.
  
  
  CONCLUSIONS
  Effect of BWS variation during robot assisted gait on muscle activities was studied by developing dynamic simulation. It is expected that the proposed dynamic simulation approach will provide important inferences and information about the muscle function variations consequent upon a change in BWS during robot assisted gait. This information shall be quite important while investigating the influence of BWS intonation on neuromuscular parameters of interest during robotic gait training.
authors.affiliation: a School of Mechanical, Materials and Mechatronics Engineering , University of Wollongong , Wollongong , Australia.
authors.forename: Shahid
authors.initials: S
authors.lastname: Hussain
authors.affiliation: b Department of Electrical and Electronics Engineering , Nazarbayev University , Astana , Kazakhstan.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Jamwal
authors.affiliation: c School of Mechanical Engineering , University of Adelaide , Adelaide , Australia.
authors.forename: Mergen H
authors.initials: MH
authors.lastname: Ghayesh
mesh_terms: D000843:Ankle Joint / Q000503:physiopathology; D001696:Biomechanical Phenomena; D001835:Body Weight / Q000502:physiology*; D003198:Computer Simulation; D005684:Gait / Q000502:physiology*; D006621:Hip Joint / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D008962:Models, Theoretical; D018482:Muscle, Skeletal / Q000502:physiology*; D009989:Orthotic Devices; D012371:Robotics; D019415:Torque
keywords: Body weight support; dynamic simulation; gait training; muscle activity patterns; robotic orthosis