Motion capture system

Kinematic measurements on motion smoothness and body trunk compensations were conducted by a motion capture system (Vicon Motion Systems, Oxford, UK) based on the standard marker configuration on the upper limb and body trunk [28 (link)].
The participants were required to perform the same bare-arm testing trials as in the EMG evaluation with a repetition of 3 times for each task. A break of 2 min between two consecutive trials was adopted to prevent fatigue. The number of movement units (NMUs) and maximal trunk displacement (MTD) were adopted to evaluate the motion smoothness and compensatory trunk movement. NMUs were the cumulated counts of signified change in the tangential velocity of the middle finger’s metacarpophalangeal joint in the testing trials [29 (link)], and an increase in NMUs indicated a decrease in movement smoothness. The MTD quantified the trunk displacements in the 3-dimensional space during the bare-arm testing trials with respect to an initial starting position [29 (link)]. The maximum value in any dimension of a testing trial was adopted as an MTD reading.

The experimental group was tested in two stages: one on the day before surgery (BCI—before cochlear implantation) and the other three months after implantation (ACI—after cochlear implantation). In the first case participants were not using hearing aids, and in the second their cochlear implant was turned off. The control group, in turn, was tested once.
Gait studies were conducted using a motion capture system (Vicon Motion Systems Ltd, Oxford, UK). First, anthropometric measurements were taken for each person. Next, spherical markers were placed at anatomical landmarks, according to the standards of the biomechanical model Plug-In-Gait available within the Vicon system. A motion capture system, consisting of nine infrared cameras, was employed to collect kinematics data at a sampling rate of 100 Hz. The system was precalibrated according to the manufacturer's recommendations. Each subject performed three trials of unassisted walking at their preferred walking speed along a 10m walkway. For each individual, one trial, performed naturally and without any random mistakes (without recording errors or problems with markers, without the subject stopping for some reason, failing to reach the end of the path, etc.) was selected and taken into account for further analysis.

The VRT group trained on the Gait Real-time Analysis Interactive Lab (GRAIL; Motekforce Link, Amsterdam, the Netherlands). The GRAIL consists of an instrumented dual-belt treadmill combined with a motion-capture system (Vicon Motion Systems, Oxford, UK) and a 180° semi-cylindrical screen for the projection of synchronized 3-dimensional environments. To create a safe environment, participants wore a harness without providing weight support. Various rehabilitative applications (VR environments) with specific rehabilitation goals were available (eg, to train reactive balance, maneuverability, or dual tasks). Difficulty level could be further modified within the applications by adjusting multiple training options: duration, treadmill speed, pitch and sway of the treadmill, belt acceleration or deceleration, amount of simultaneous tasks, frequency and position of environmental constrains (eg, obstacles), and the amount and type of real-time feedback. VRT was conducted by specialized therapists who are trained to work with the GRAIL. The therapist chose, based on the therapeutic goals, which applications were used during a training session and could easily adapt the difficulty level to individual abilities of the participants.

The movements were recorded with a motion capture system (Vicon Motion Systems Ltd., UK) with three camera. Reflective markers were attached overlying iliac crest, greater trochanter (hip joint), lateral condyle of the femur (knee joint), lateral malleolus (ankle joint), and the distal end of the fifth metatarsophalangeal (MTP) joint of the cats. The temporal sampling rate was 100 Hz. During each trial of the experiment, an operator moved the foot of the cat in a stepping-like pattern. Having the distance between marker positions, hip, knee, and ankle angles were extracted using the law of cosines. Each recording session consisted of 10 trials of experiment and each recording trial lasted for 5 minutes.

A custom-made timer was pressed by the subject to indicate the start and end of each trial. The subject reported the task completion time to the experimenter. Cable operation forces were measured at both the forearm and back of the subject. Forces were measured with two mini S beam 222N load cells (FUTEK Advanced Sensor Technology, Inc., Irvine, United States), amplified with a CPS amplifier (SCAIME S.A.S., Juvigny, France) and fed into the analogue input of a motion capture system (Vicon Motion Systems Ltd., Oxford, United Kingdom) at 1000 Hz. The signals were recorded using Nexus 1.8.3 software (Vicon Motion Systems Ltd., Oxford, UK), and stored for off-line analysis after each trial. The recorded motion capture data were not used for the current study.

The patients underwent kinematic (motion capture system: Vicon Motion Systems Ltd., Oxford, UK) and kinetic (force platforms: Kistler Group, Winterthur, CH) 3D gait analysis before BTX-A injection and 6 weeks (6.1 [range 5.4–6.9] weeks) and 12 weeks (12.3 [range 11.4–12.9] weeks) after BTX-A injection. TD children participated in a single measurement session. Gait data were measured barefoot at a self-selected speed using the Plug-in Gait lower-body marker-set [34 (link)] until six valid kinetic datasets for each leg were acquired. During each clinical gait analysis, a physical examination was performed, including a test of the passive range of motion, a manual muscle strength test (MMST), and an assessment of spasticity (modified Ashworth scale).

Nine healthy adult subjects (four males, five females; age 30.1 ± 3.7 years) without a history of neurologic or orthopedic disorders underwent kinematic (motion capture system: Vicon Motion Systems Ltd., Oxford, UK) and kinetic (force platforms: Kistler Group, Winterthur, CH) 3D gait analysis, as part of a previous study (Romkes and Brunner, 2007 (link)). Gait data were acquired barefoot at a self-selected speed using the Plug-in Gait lower-body marker-set (Kadaba et al., 1990 (link)). One of the ten healthy subjects originally included in Romkes and Brunner (2007) (link) was excluded due to an incomplete set of markers. Subjects were first tested during normal walking and were then shown a sagittal plane video of a patient with unilateral CP. They were asked to mimic the unilateral toe walking pattern seen in the video. The subjects practiced until obtaining a reproducible pattern, while care was taken by the investigators to ensure that knee and ankle positions were correct. Four to six walking trials were measured for each walking modality per subject. Further details on the experimental data collection can be found in Romkes and Brunner (2007 (link)).