Lecture 10 Flashcards
What is Musculoskeletal modelling?
A model of the human body that allows to simulate its movement
Used to:
- Estimate unmeasurable quantities e.g. muscle forces, joint loads, & ligament strains
- Understand complex biomechanics
- Predict movement outcomes under various conditions
What does the intersegmental (Net Joint) Moment indicate?
Represents the torque required to achieve the observed motion.
Does NOT capture the magnitude of internal forces (e.g. muscle or ligament contributiions)
What does the Joint Reaction (internal) moment indicate?
Reflects the load transmitted across the joint
Also includes passive contributions from ligaments and cartilage
Which muscles are active to stabilise the pelvis?
The hip abductors (e.g. gluteus medius)
The hip adductors contract simultaneously for joint stabilisation
The forces created from these muscles produce significant internal moments that are not fully reflected in the net moment (due to opposing direction)
What is the equation to determine force generated by/in a muscle?
F = Activation x F₀
Activation: Degree of activation (between 0 and 1)
F₀ (max. isometric force): Maximum force a muscle can generate when fully activated without changing length
Which muscuskeletal modelling sub-technique/s only requires gait analysis data to work?
- Inverse kinematics
- Muscle lengths
What can muscuskeletal modelling do/be used for? (7 answers)
- Inverse kinematics
- Muscle length estimation
- Inverse dynamics
- Muscle activation
- Joint reaction
- Induced acceration
- Forward dynamics (predictive simulation)
Which muscuskeletal modelling sub-technique/s only requires Ground reaction forces (GRFs) to work?
Inverse dynamics
Which muscuskeletal modelling sub-technique/s only be completed with muscuskeletal modelling?
- Muscle activation measurements
- Joint reaction
- Induced acceleration
What is the muscle redundancy problem?
This issue arises because the human MSK system is overactuated: There are typically more muscles crossing a joint than are mathematically necessary to produce a desired joint torque.
THIS MEANS there are infinite combinations of muscle forces that could produce the same motion or joint torque
What is Induced Acceleration Analysis (IAA)?
Biomechanical technique used to calculate how individual forces in Muscuskeletal model contribute to the acceleration of body segments or joints
What is the difference between Backward and forward dynamics?
Backward dynamics:
From the movement and what caused it, we can estimate muscle activation
Forward dynamics:
The muscle activation is prescribed. From those, we move the muscle of the model to achieve a movement
What are the main predictive modelling architectures?
- Control policy definition
- Trajectory optimisation
Why has predictive modelling not been implemented in clinical gait analysis yet? (5 Answers)
- Movement data alone doesn’t provide the answer
- Every patient is unique
- People change over time
- Validation is often weak
- Prediction of post treatment function is difficult
Whta is an application of inverse kinematics? (6 answers)
- Muscle lengths
- Bone deformity
- Tendon transfer
- Joint reaction loads
- induced acceleration
- Muscle contribution
Why is scaling important in muscuskeletal modelling?
- Growth and development differences (child vs adult)
- Children have lower strength and have lower force generation than adults
How can muscle redundancy be resolved? 3.5 answers
- Using inverse dynamics and muscuskeletal simulations/models
- Minimum activation assumption (assume the body uses smallest possible muscle forces to schieve the movement)
- EMG-driven models
