Paper model definition... some help and is it available ?

[Andrea Morelli]

I was reading the paper

"Elevated gastrocnemius forces compensate for decreased hamstrings forces during the weight-acceptance phase of single-leg jump landing: implications for anterior cruciate ligament injury risk"

from Kristin D. Morgan, Cyril J. Donnelly, Jeffrey A. Reinbolt

(very nice and interesting articles by the way)

In the model definition I read:

"Six three-dimensional, 14-segment, 37 degree-of-freedom (DoF), 92 muscle- tendon actuated subject-specific models were created in OpenSim 1.9.1 (Delp et al., 1990) to generate simulations of each participant performing the landing task (Fig. 1). The details of this model have been described previously (Donnelly et al., 2012b). The 92 muscle-tendon units actuated the lower extremities and lower back joints, while the arms were actuated by torque actuators described previously (Hamner et al., 2010). The maximum isometric force of each muscle was increased by 60% compared to the generic OpenSim model based on research by Arnold et al. (2010). The model included a 5 DoF knee that rotated about all three planes. Sagittal and transverse plane translations were modeled as a function of knee angle (Donnelly et al., 2012b, Delp et al., 1990). The knee was actuated by muscles and ideal torque actuators ( +/- 50 Nm), the values are consistent with previous literature that provided the resistance supplied by the knee ligaments and articular surface that help support the knee in the frontal plane (Seedhom et al., 1972; Zhao et al., 2007). An ACL was included in the model and scaled to each participant. The ligament model was described in a previous study (Xu et al., 2014). Subject-specific joint centers were derived using functional knee and hip joint methods (Besier et al., 2003), custom biomechanical models in MATLAB (MATLAB 7.8, The MathWorks, Inc., Natick Massachusetts, USA) and Vicon Bodybuilder (Dempsey et al., 2007)."

1) Is the model available ?
2) How doe the ideal torque actuator works ? ("The knee was actuated by muscles and ideal torque actuators ( +/- 50 Nm)")
3) How do you include it into the model ? At the muscle level or ligament ?
4) How I can include the tibial anterior/posterior translation is linked with the knee extension angle? There's any equation available or example ?
5) Why the medial/lateral tibial translation was not included )
6) Why compared to other simulation I see like drop landing/skyjump there's no contact forces/surfaces ? When they are useful ?

sorry for so much question...

Thank you
Andrea

[jimmy d]

Have you tried emailing the Authors? There should be contact information of the corresponding Author in the paper.

[Andrea Morelli]

Hi James.
Thank you for your reply.
I will try to contact also the author.
I did post here because I think lot of people can be interested about the model and my "question" and can contribute to that.
Thank you
Andrea