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The Gait 2392 Model and Gait 2354 Model are three-dimensional, 23 degree-of-freedom computer model of the human musculoskeletal system. The models were created by Darryl Thelen, Univ. of Wisconsin-Madison, and Ajay Seth, Frank C. Anderson, and Scott L. Delp, Stanford University. The models feature lower extremity joint definitions adopted from Delp et al. (1990), low back joint and anthropometry adopted from Anderson and Pandy et al. (1999), and a planar knee model adopted from Yamaguchi and Zajac etal. (1989).
The Gait 2392 model features 92 musculotendon actuators to represent 76 muscles in the lower extremities and torso. For the Gait 2354 model, the number of muscles was reduced by Anderson to improve simulation speed for demonstrations and educational purposes. Seth removed the patella to avoid kinematic constraints; insertions of the quadrucepts are handled with moving points in the tibia frame.
The default, unscaled version of the models a subject that is about 1.8 m tall and weighs 75.16 kilograms.
The models can be used and modified in OpenSim, an open source biomechanics simulation application. Some of the uses of the models include:
- Computing the maximum isometric force and joint moment a muscle can develop at any body position
- Studying how surgical changes in musculoskeletal geometry (e.g. origin-to-insertion path) and muscle-tendon parameters (e.g. optimal muscle-fiber length and tendon slack length) can affect the moment-generating capacity of the different muscles on the human body
- Generating muscle drive forward simulations of walking and running to analyze how muscles contribute to motions (e.g. Induced Acceleration Analysis) or how joints are loaded (see Joint Reactions Analysis).
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Experimental Data Included with the Models
The experimental data included with the model files in the OpenSim distribution was collected as part of the study cited below. Please note that the data distributed with OpenSim is from a different subject than the one described in the paper. Data collection protocols were the same for both subjects.
Chand T. John, Frank C. Anderson, Jill S. Higginson & Scott L. Delp (2012): Stabilisation of walking by intrinsic muscle properties revealed in a three-dimensional muscle-driven simulation, Computer Methods in Biomechanics and Biomedical Engineering, DOI:10.1080/10255842.2011.627560. Download here
Accessing the Models
The musculoskeletal file (.osim), the setting files (.xml), and associated result files (.mot, .sto) for this model are provided free of charge with the OpenSim software for researchers interest in reproducing the result of the simulation. These files can be accessed via the Models/Gait2392_Simbody or Models/Gait2354_Simbody folder in the OpenSim 3.0 installation directory, and the example/Gait2392_Simbody or Models/Gait2392_Simbody folder in the OpenSim 2.4.0 installation directory.
Kinematics
Bone geometry
Bones surface data for the pelvis and the thigh are obtained by first marking the surfaces of bones with a mesh of polygons, and then determining the coordinates of the vertices with a three-dimensional digitizer. Data describing the shank and foot bones are adopted from Stredney et al (1982).
Joint geometry
The lower extremity has seven right-body segments: pelvis, femur, patella, tibia/fibula, talus, foot (which includes the calcaneus, navicular, cuboid, cuneiforms, metatarsals), and toes. Reference frames are fixed in each segment.
Figure 1 Location of the body-segmental reference frames (Delp et al., 1990).
- Pelvis: The pelvic reference frame is fixed at the midpoint of the line connecting the two anterior superior iliac spines
- Femur: The femoral frame is fixed at the center of the femoral head
- Tibia: The tibial frame is located at the midpoint of the line between the medial and lateral femoral epicondyles
- Patella: The patellar frame is located at the most distal point of the patella
- Talus: The talar frame is located at the midpoint of the line between the apices of the medical and lateral malleoli
- Calcanus: The calcaneal frame is located at the most interior, lateral point on the posterior surface of the calcanus
- Toe: The toe frame is located at the base of the second metatarsal
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Overview and Authors
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The Gait2392 and Gait2354 models are three-dimensional, 23-degree-of-freedom computer models of the human musculoskeletal system. The models were created by Darryl Thelen (University of Wisconsin-Madison) and Ajay Seth, Frank C. Anderson, and Scott L. Delp (Stanford University). The models feature lower extremity joint definitions adopted from Delp et al. (1990), low back joint and anthropometry adopted from Anderson and Pandy (1999), and a planar knee model adopted from Yamaguchi and Zajac (1989). The Gait2392 model features 92 musculotendon actuators to represent 76 muscles in the lower extremities and torso. For the Gait2354 model, the number of muscles was reduced by Anderson to improve simulation speed for demonstrations and educational purposes. Seth removed the patella to avoid kinematic constraints; insertions of the quadriceps are handled with moving points in the tibia frame. The default, unscaled version of these models represents a subject that is about 1.8 m tall and has a mass of 75.16 kg. |
The models can be used and modified in OpenSim, an open source biomechanics simulation application. Some of the uses of the models include:
- Computing the maximum isometric force and joint moment a muscle can develop at any body position
- Studying how surgical changes in musculoskeletal geometry (e.g. origin-to-insertion path) and muscle-tendon parameters (e.g. optimal muscle-fiber length and tendon slack length) can affect the moment-generating capacity of the different muscles on the human body
- Generating muscle drive forward simulations of walking and running to analyze how muscles contribute to motions (e.g. Induced Acceleration Analysis) or how joints are loaded (see Joint Reactions Analysis).
| Table of Contents | ||
|---|---|---|
|
Experimental Data Included with the Models
The experimental data included with the model files in the OpenSim distribution was collected as part of the study cited below. Please note that the data distributed with OpenSim is from a different subject than the one described in the paper. Data collection protocols were the same for both subjects.
Chand T. John, Frank C. Anderson, Jill S. Higginson & Scott L. Delp (2012): Stabilisation of walking by intrinsic muscle properties revealed in a three-dimensional muscle-driven simulation, Computer Methods in Biomechanics and Biomedical Engineering, DOI:10.1080/10255842.2011.627560. Download here
Accessing the Models
The musculoskeletal file (.osim), the setting files (.xml), and associated result files (.mot, .sto) for this model are provided free of charge with the OpenSim software for researchers interest in reproducing the result of the simulation. These files can be accessed via the Models/Gait2392_Simbody or Models/Gait2354_Simbody folder in the OpenSim 3.0 installation directory, and the example/Gait2392_Simbody or Models/Gait2392_Simbody folder in the OpenSim 2.4.0 installation directory.
Kinematics
Bone geometry
Bones surface data for the pelvis and the thigh are obtained by first marking the surfaces of bones with a mesh of polygons, and then determining the coordinates of the vertices with a three-dimensional digitizer. Data describing the shank and foot bones are adopted from Stredney et al (1982).
Joint geometry
The lower extremity has seven right-body segments: pelvis, femur, patella, tibia/fibula, talus, foot (which includes the calcaneus, navicular, cuboid, cuneiforms, metatarsals), and toes. Reference frames are fixed in each segment.
Figure 1 Location of the body-segmental reference frames (Delp et al., 1990).
- Pelvis: The pelvic reference frame is fixed at the midpoint of the line connecting the two anterior superior iliac spines
- Femur: The femoral frame is fixed at the center of the femoral head
- Tibia: The tibial frame is located at the midpoint of the line between the medial and lateral femoral epicondyles
- Patella: The patellar frame is located at the most distal point of the patella
- Talus: The talar frame is located at the midpoint of the line between the apices of the medical and lateral malleoli
- Calcanus: The calcaneal frame is located at the most interior, lateral point on the posterior surface of the calcanus
- Toe: The toe frame is located at the base of the second metatarsal
Models of the hip, knee, ankle, subtalar, and metatarsophalangeal joints define the relative motions of these segments.
Pelvic Tilt and Hip Flexion Angle (Gait2354 vs. Clinical Measurements)
The pelvic frame is located midway between the two ASIS. In the neutral position, the model has zero pelvic tilt with respect to ground (or lab). In other words, the pelvic frame and ground frame are aligned at neutral (pelvic tilt = 0 degrees). In many clinical papers, neutral corresponds to 12-13 degrees of pelvic tilt. This will lead to an offset when comparing pelvic tilt and hip flexion angles from the gait2354 model to some data from clinical papers or gait analysis lab data.
To compare angles from the gait2354 model to clinical data, you can subtract the angle formed between the horizontal plane and a line between the ASIS and PSIS markers from the clinical pelvic tilt measurements. You should also add this value to the clinical hip flexion measurement. If angle formed between the horizontal plane and a line between the ASIS and PSIS markers is not known, a value of 12-13 degrees is typical.
Hip Joint
The hip is characterized as a ball-and-socket joint. The transformation between the pelvic and femoral reference frame is thus determined by successive rotations of the femoral frame about three orthogonal axes fixed in the femoral head.
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The ankle, subtalar, and metatarsophalangeal joints are modeled as frictionless revolute joints (as seen in Figure 3).
Figure 3. The ankle, subtalar, and metatarphalangeal joints are modeled as revolute joints with axes oriented as shown. (Delp et al., 1990)
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Table 2: Inertial parameters for the body segments included in the model
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Body segment | Mass (kg) | Moments of inertia | ||
xx | yy | zz
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Torso | 34.2366 | 1.4745 | 0.7555 | 1.4314 |
Pelvis | 11.777 | 0.1028 | 0.0871 | 0.0579 |
Right femur | 9.3014 | 0.1339 | 0.0351 | 0.1412 |
Right tibia | 3.7075 | 0.0504 | 0.0051 | 0.0511 |
Right patella | 0.0862 | 0.00000287 | 0.00001311 | 0.00001311 |
Right talus | 0.1000 | 0.0010 | 0.0010 | 0.0010 |
Right calcaneus | 1.250 | 0.0014 | 0.0039 | 0.0041 |
Right toe | 0.2166 | 0.0001 | 0.0002 | 0.0010 |
Left femur | 9.3014 | 0.1339 | 0.0351 | 0.1412 |
Left tibia | 3.7075 | 0.0504 | 0.0051 | 0.0511 |
Left patella | 0.0862 | 0.00000287 | 0.00001311 | 0.00001311 |
Left talus | 0.1000 | 0.0010 | 0.0010 | 0.0010 |
Left calcaneus | 1.250 | 0.0014 | 0.0039 | 0.0041 |
Left toe | 0.2166 | 0.0001 | 0.0002 | 0.0010 |
Actuators and Other Force-Generating Elements
Peak isometric force
In the original lower limb model developed by Delp et al. (1990), values for the muscle-tendon parameters are determined with a procedure similar to that used by Hoy et al. (1990). Values for muscle physiological cross-sectional area (PCSA), which determine the peak isometric force, are taken from Friederich et al. (1990) and Wickiewicz (1983). Because the measurements reported by Friederich et al. (1990) [25 N-m2] are obtained from experiments on young cadavers, and those reported by Wickiewicz et al. (1983) [61 N-m2 ] are obtained from experiments on elderly cadavers, a factor that is larger than the “specific tension” reported by Spector at al. (1980) [23 N-m2] is used to scale the PCSA values from the elderly cadavers.
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.250 | 0.0014 | 0.0039 | 0.0041 | |
Left toe | 0.2166 | 0.0001 | 0.0002 | 0.0010 |
Actuators and Other Force-Generating Elements
The gait2392 model Includes the 43 muscles specified in the Delp leg model and the 6 lumbar muscles included in Anderson's gait model.
Peak isometric force
In the original lower limb model developed by Delp et al. (1990), values for the muscle-tendon parameters are determined with a procedure similar to that used by Hoy et al. (1990). Values for muscle physiological cross-sectional area (PCSA), which determine the peak isometric force, are taken from Friederich et al. (1990) and Wickiewicz (1983). Because the measurements reported by Friederich et al. (1990) [25 N-m2] are obtained from experiments on young cadavers, and those reported by Wickiewicz et al. (1983) [61 N-m2 ] are obtained from experiments on elderly cadavers, a factor that is larger than the “specific tension” reported by Spector at al. (1980) [23 N-m2] is used to scale the PCSA values from the elderly cadavers.
While constructing the Gait 2392 Model from the original Delp model, Anderson noticed that the muscle strengths in the Delp model were still weak compared to the experimental results from Anderson and Pandy (1999) and Carhart (2000) on healthy, living subjects. To better match the strength of the Delp model to the joint torque-angle relationships measured in living subjects, additional strength scaling was employed. Despite efforts to keep the scaling factor consistent across all muscles, a different scaling factor is needed for bi-articular muscles because they span two joints. In many cases, the muscle strength parameters from Anderson and Pandy are used instead, as they are more physiologically accurate.
For details, refer to the following PDF of the maximum isometric muscle forces from Gait2392/Gait2354, Delp1990, and Carhart2000, along with the scale factors: MuscleIsometricForces.pdf. We also conducted a comparison of CMC results from the Gait2392 walking example was made between the "scaled" Gait2392 and isometric forces from Delp (1990): Gait2392ComparisonResultsCMC.pdf. Note, that the muscles activations predicted by CMC were not significantly different between the two sets of isometric muscle force. Therefore,we do not expect these increases would greatly affect the distribution of muscle force estimates, nor the interpretation of those results.
Optimal fiber length and pennation angle
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Hoy, M. G., Zajac, F. E., and Gordon, M. E., "A musculoskeletal model of the human lower extremity: the effect of muscle, tendon, and moment ann on the moment-angle relationship of musculotendon actuators at the hip, knee, and ankle," J. Biomech., vol. 23, pp. 157-169, 1990.