Specimens were attached to a universal testing machine (MTS 30/G) using specially designed holding jigs. Flexion, extension, and lateral bending were attained by applying a 200 N load at a rate of 2 mm/sec to the loading arm connecting the cup containing the thoracic end of the spine while the cup with the sacral end was fixed to the base of the loading frame (Fig. 1A ). Axial rotation of ±8° of the specimen was achieved by coupling the thoracic end to a servo motor rotating at 2°/sec with the sacral end fixed (Fig. 1B ). A 50N preload (follower load) was applied from L1 to L5. During all testing, 3-dimensional specimen motion was recorded using an optical motion-tracking device (Optotrak, Northern Digital Inc., Waterloo, ON, Canada). The apparatus was designed to apply compressive follower preload representing the physiologic preload acting in the lumbar spine and maintaining the spine alignment. This was applied using bilateral cables passing freely through guides anchored to each vertebra. Additional load for flexion and extension was applied with a compressive force that varied between 200–300 N with a lever arm of 1.5 cm and allowed for a combined moment of 4.5–6 Nm. Most of the reported experiments using the follower method reported a pure moment load between 4–8 Nm.
Optotrak
Manufactured by Northern Digital
Sourced in Canada
The Optotrak is a motion capture system designed for precise measurement and tracking of 3D movement. It utilizes optical sensors to capture the position and orientation of markers placed on objects or individuals. The Optotrak provides accurate data on the real-time movement of these markers, which can be used for various applications.
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Lab products found in correlation
22 protocols using optotrak
1
Biomechanical Testing of Spinal Segments
2
Wheelchair-Based Kinematic Analysis
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Kinematic data were collected using an optoelectronic camera system (Optotrak, Northern Digital, Waterloo, Canada) at 100Hz with technical cluster markers attached to the right side of the participant’s body and to the rigid frame of the wheelchair (Fig 3 ). The location of anatomical landmarks was determined in relation to their technical clusters. Based on this calibration procedure, the positions of the anatomical landmarks were reconstructed for each participant (Fig 3 ) and used to create the joint coordinate systems of the shoulder, elbow and wrist [14 (link)]. The location of the rotation center of the glenohumeral joint was calculated using the regression method proposed by Meskers et al. [15 (link)].
3
Kinematic Analysis of Lifting and Walking
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To analyse movement patterns during lifting and walking, we recorded 3D kinematics with an optoelectronic motion capture system (Optotrak, Northern Digital Inc., Waterloo ON, Canada) at a sample rate of 50 Hz. In the lifting trials, segment kinematics were measured using a dynamic three-dimensional linked segment model (Kingma et al. 2010) (link). Cluster markers were attached to lower and upper leg, pelvis, trunk, upper and lower arm, head and box. Due to the fact that participants performed symmetric lifting, we only recorded kinematics from the right side of the body. To define the local segmental coordinate systems, anatomical landmarks were located through palpation and were related to the respective cluster markers using separate measurements (cf. Kingma et al. 2010 (link)). In the walking trial, only stride parameters were recorded using single heel markers attached to both shoes.
4
Tracking Jaw and Hand Movements in Stuttering
5
Vibration-Assisted Gait Biomechanics Protocol
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To apply HA vibration, a pair of custom-made mechanical vibrators was used, which consisted of two encased electromotors (Graphite Brushes S2326.946, Maxon, Sachseln, Switzerland) with an eccentric mass attached to the motor axis, driven in a velocity loop at 90 Hz (4-Q-DC Servo Control LSC 30/2, Maxon, Sachseln, Switzerland). Vibrators were bilaterally placed at 50% of the distance between the iliac crest and the greater trochanter of the femur and were tightly attached with an elastic strap. Custom-made software controlled the vibrators to allow stimulation to be coupled to the kinematics in the gait trials.
Kinematic data were collected using Optotrak (Northern Digital Inc., Waterloo, Canada). Optotrak LED marker clusters were attached with elastic straps and tape on the posterior surface of both heels, shanks, thighs, the sacrum, and the thorax at the midpoint between the scapulas. Marker locations were tracked by two Optotrak camera systems and digitized at 50 samples/s. Ground reaction force data were measured by two force plates embedded in the treadmill (ForceLink, Culemborg, Netherlands) and digitized at 200 samples/s. The force time series were down-sampled to be synchronized with the kinematic data. Kinematic and force data were low-pass filtered with a cut-off frequency of 5 Hz.
Kinematic data were collected using Optotrak (Northern Digital Inc., Waterloo, Canada). Optotrak LED marker clusters were attached with elastic straps and tape on the posterior surface of both heels, shanks, thighs, the sacrum, and the thorax at the midpoint between the scapulas. Marker locations were tracked by two Optotrak camera systems and digitized at 50 samples/s. Ground reaction force data were measured by two force plates embedded in the treadmill (ForceLink, Culemborg, Netherlands) and digitized at 200 samples/s. The force time series were down-sampled to be synchronized with the kinematic data. Kinematic and force data were low-pass filtered with a cut-off frequency of 5 Hz.
6
Kinematic Analysis of Human Gait
7
Aligning Motion Tracking System to Specimen
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To align the motion tracking system (3D Investigator and Optotrak systems by Northern Digital Inc., Waterloo, ON, Canada) to the physiological coordinate system of the specimen, a probe was used to digitize the extents of the sacral ala and the moment ring. The lateral axis was defined as the line connecting the left and right lateral extents of the moment ring (installed on the L4 vertebrae). The A–P axis was defined as the line connecting the anterior extent of the moment ring to the midpoint of lateral axis line. The combination of these two axes defined the transverse plane. And the origin was moved to the apex of the sacral ala. The Infrared motion markers were rigidly attached to the iliac brim and second sacral body [8 (link)–13 (link)].
Data from the markers were recorded during each loading interval at 100 Hz and a custom computer program executed by commercial software (MATLAB by MathWorks) extracted the peak motion observed during data collection from the raw data files. These data were used to find the range of motion in flexion–extension, lateral bending, and axial rotation in an intact, unilateral, and bilateral state for each specimen.
Data from the markers were recorded during each loading interval at 100 Hz and a custom computer program executed by commercial software (MATLAB by MathWorks) extracted the peak motion observed during data collection from the raw data files. These data were used to find the range of motion in flexion–extension, lateral bending, and axial rotation in an intact, unilateral, and bilateral state for each specimen.
8
Split-Belt Treadmill Kinematics Analysis
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Participants walked on a split-belt treadmill (Woodway, Waukesha, WI, USA) and belt speeds were controlled using a custom Vizard program (WorldViz). Kinematic data were collected using infrared-emitting markers (Optotrak, Northern Digital, Waterloo, ON, Canada) at 100Hz (SI Appendix , Supplementary Methods ).
9
Measuring Acetabular Fragment Stability
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The relative displacement of each fragment was measured using a 3D motion capture system (Optotrak, Northern Digital, Waterloo, ON). Load/displacement curves were plotted and analyzed for initial stiffness and the ultimate strength. Each specimen was then subjected to load-to-failure in stroke control at a rate of 20 mm/second while recording the applied load and relative displacements of each fragment. Failure was defined as a fracture of the sawbones model, screw pull-out, fracture of the screw, or displacement of the acetabular fragment by more than a centimeter. Ultimate strength (load force at point of failure) measured in Newton (N) and initial stiffness (N/mm) were compared between each construct group.
10
Kinematics of Active Wheelchair Propulsion
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Kinematic data were collected using an optoelectronic camera system (Optotrak, Northern Digital, Waterloo, Canada) at 100Hz with technical cluster markers attached to the right side of the participants’ body and to the wheelchair (Figure 2 , left). Prior to the actual experiment, a calibration measurement was performed to determine the location of anatomical landmarks in relation to their technical clusters. From these calibrations, the positions of the anatomical landmarks were reconstructed during the experiment (Figure 2 , right), which in turn were used to construct joint coordinate systems of the shoulder, elbow and wrist [27 (link)]. The location of the glenohumeral (GH) rotation point was calculated using the regression method proposed by Meskers et al. [28 (link)].![]()
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