Amplitude threshold criteria improve surface electrode specificity during walking and functional movements.

Contamination of electromyographic (EMG) data due to crosstalk in recordings from surface electrodes can lead to misinterpretation of results. The purpose of this study was to determine if removing a portion of the EMG signal normalized to a maximum voluntary contraction (MVC) would improve the specificity of surface electrode recordings. We hypothesized that setting an amplitude threshold to define when a muscle was active would remove that part of the myoelectric signal most likely to include crosstalk, without affecting the intensity or the onset and cessation times. Surface and intramuscular electrodes recorded signals from the same muscles of adults performing cyclic ankle movements and walking at self-selected speeds. Signals identified as crosstalk were eliminated when 15% and 18% of the amplitude of the normalized signal was removed and muscle timing or intensity was not significantly changed in most cases.

The kinematic and kinetic effects of solid, hinged, and no ankle-foot orthoses on stair locomotion in healthy adults.

This study compared the effects of a unilateral solid ankle-foot orthosis (AFO), hinged AFO and no AFO (shoe) worn by healthy adults on pelvic angles, lower extremity joint angles, moments and powers, and temporal-spatial gait characteristics during stair locomotion. A convenience sample of 19 healthy adults participated in this repeated measures design with subjects serving as their own controls. Subjects ambulated on stairs wearing a left shoe and either a right solid AFO, hinged AFO or shoe. Kinematic and kinetic data were collected with motion analysis equipment and a force plate for the three conditions. Pelvic angles and right hip, knee and ankle angles, moments and powers during stance were compared to determine differences among the conditions. Subjects wearing either orthosis walked slower during stair locomotion and with a shorter right single limb support time during descent. Sagittal knee and ankle angles, moments and powers were similar in individuals wearing a hinged AFO or shoe during pull-up (PU) in ascent and controlled lowering (CL) in descent. Decreased ankle dorsiflexion angle, plantar flexion power, knee flexion angle and extensor moment were seen in subjects wearing a solid AFO as compared to a hinged AFO during PU in ascent and CL in descent. Findings contributed to understanding how biomechanical changes imposed at the ankle by a unilateral solid AFO resulted in more kinetic and kinematic compensations than the hinged AFO in healthy adults without the confounding effects of neuromuscular impairments.

A comparison of gait with solid and hinged ankle-foot orthoses in children with spastic diplegic cerebral palsy.

This study compared the effects of solid and hinged ankle-foot orthoses (AFOs) on the gait of children with spastic diplegic cerebral palsy (CP) who ambulate with excessive ankle plantar flexion during stance. Twelve children with spastic diplegic CP wore no AFOs for an initial 2-week period, solid AFOs for 1 month, no AFOs for 2 weeks, and hinged AFOs for 1 month. Lower extremity muscle timing, knee and ankle joint motions, moments and powers, and temporal-distance characteristics were measured during ambulation for an initial barefoot baseline test, and with solid and hinged AFOs for the other two tests. Both orthoses increased stride length, reduced abnormal ankle plantar flexion during initial contact, midstance and terminal stance (TST), and increased ankle plantar flexor moments closer to normal during TST. Hinged AFOs increased ankle dorsiflexion at TST and increased ankle power generation during preswing (PSW) as compared to solid AFOs, and increased ankle dorsiflexion at loading compared to no AFOs. No other significant differences were found for the gait variables when comparing these orthoses. Either AFO could be used to reduce the excessive ankle plantar flexion without affecting the knee position during stance. The hinged AFO would be recommended to produce more normal dorsiflexion during TST and increased ankle power generation during PSW in children with spastic diplegic CP.