title: Muscle activation patterns during walking from transtibial amputees recorded within the residual limb-prosthetic interface.
abstract: BACKGROUND
  Powered lower limb prostheses could be more functional if they had access to feedforward control signals from the user's nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking.
  
  
  METHODS
  We recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step inter-subject variability of these profiles by calculating variance-to-signal ratios.
  
  
  RESULTS
  We found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects.
  
  
  CONCLUSIONS
  Robotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee's nervous system.
authors.affiliation: Human Neuromechanics Laboratory, University of Michigan, 401 Washtenaw Ave, Ann Arbor, MI 48109-2214, USA. shuangz@umich.edu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Huang
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Ferris
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000671:Amputation, Surgical / Q000534:rehabilitation*; D001186:Artificial Limbs; D001696:Biomechanical Phenomena; D004566:Electrodes; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology*; D011999:Recruitment, Neurophysiological / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D013977:Tibia; D016138:Walking / Q000502:physiology*; D055815:Young Adult