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Accuracy of the Microsoft Kinect in Measurement of the Trunk Kinematics for the Analyze of Load in Musculoskeletal Models

Asadi, Fatemeh | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52964 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Arjmand, Navid
  7. Abstract:
  8. Low back pain is one of the most prevalent musculoskeletal injuries in occupational activities. In order to reduce or prevent it, it is necessary to estimate the mechanical loads of body joints. Direct measurement of spinal loads is invasive and costly. Therefore, musculoskeletal modeling is a convenient tool in estimation of joints and muscles loads that often uses kinematics information as input.Marker-based motion capture systems are one of the most common ways for the estimation of body kinematics. Unfortunately, they are time consuming and expensive. Thus being marker-free and low-cost, Microsoft Kinect is a suitable alternative. Recent studies often have investigated accuracy of Kinect in qualitative estimation of risks injuries without using musculoskeletal modeling. Furthermore, Activities in these studies were simple and special. Accordingly, the purpose of this study is accuracy of the Microsoft Kinect in measurement of the trunk kinematics for the analyze of load in musculoskeletal models during various occupational activities.Three healthy young male individuals with no history of back pain or surgery volunteered for the study. Each subject performed 18 tasks by reaching at 6 different anterior-right positions and at 3 different heights (i.e., z=0,60 and 120 cm from the floor). Tasks simultaneously captured by Kinect v2 and Vicon motion capture system. Then, upper body angles extracted and tasks simulated in AnyBody software by considering two conditions: load-free and a 7 kg external load in the hands. Finally, shear and compressive forces of L5-S1 and L4-L5 discs were estimated. According to the kinematic results, as the height of the load position from the ground increases, accuracy of Kinect in measurement the angles of the upper body increases. Root mean square errors for load positions at 0, 60, and 120 cm heights are 19, 30, and 48 degrees, respectively. As the deviation angle of sagittal plane increases, accuracy of Kinect decreases. The error for the deviation angles of zero, 45, and 90 degrees are 26, 31, and 38 degrees respectively. Furthermore, as the load position approaches the body accuracy of Kinect increases. The error is 25 degrees for near-body positions and 33 degrees for far points.The results of modeling for load-free condition indicated that mean shear forces of L5-S1 and L4-L5 discs were not significantly different for two systems (p>0.05). In addition, the mean compressive forces of the two systems were significantly different and Vicon estimated the mean forces more (p<0.05). For 7 kg external load condition, except for shear mediolateral force of L5-S1 disc (p<0.05) no compressive and shear forces were significantly different (p>0.05).In conclusion, by increasing of loading heights and by decreasing deviation angle of sagittal plane, accuracy of Kinect in measurement of upper body angles increases. In addition, accuracy of Kinect for the estimation of spinal forces depends on the weight of the load carried by the person. Hence, depending on the position and weight of the load, Kinect can be a promising device in estimation of upper body kinematics and lumbar forces
  9. Keywords:
  10. Spine ; Musculoskeletal Modeling ; Low Back Pain ; Kinematic Biomechanical Indices ; Occupational Biomechanic ; Trunk Kinematics ; Anybody Software ; Kinect Sensor

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