Pathological Gait

About

This tutorial demonstrates how to investigate the effects of potential gait pathologies in a predictive simulation, based on the model by [Geyer & Herr 2010].

Weak Plantarflexors

  • Open the scenario Tutorial 5a - Pathological Gait - Weak Plantarflexors.scone

In this scenario, we override some of the model properties of the OpenSim model:

# Override model properties
Properties {
	gastroc_l { max_isometric_force.factor = 0.2 }
	gastroc_r { max_isometric_force.factor = 0.2 }
	soleus_l { max_isometric_force.factor = 0.2 }
	soleus_r { max_isometric_force.factor = 0.2 }
}

Here, we adjust the max_isometric_force parameter with a factor of 0.2. In other words: the gastroc and soleus muscles will only have 20% of their original force.

  • Optimize the scenario (Ctrl + F5)

When playing back the intermediate results, you might notice that the muscle belly in the 3D viewer will be much thinner than in the original optimization. This is because the visualization is scaled to the maximum isometric force of the model.

Short Hamstrings

  • Open the scenario Tutorial 5b - Pathological Gait - Short Hamstrings.scone

In this scenario, we override the contractile element length of the model's hamstrings:

# Override model properties
Properties {
	hamstrings_l { optimal_fiber_length.factor = 0.75 }
	hamstrings_r { optimal_fiber_length.factor = 0.75 }
}
  • Optimize the scenario (Ctrl + F5)

Hyper-reflexia

  • Open the scenario Tutorial 5c - Pathological Gait - Hyper-reflexia.scone

In this scenario we do not change any of the model parameters; instead, we add an additional ReflexController to simulate spasticity in the gastrocnemeus muscle:

# Mimick hyper-reflexia through F+ reflex in gastroc
ReflexController {
	symmetric = 1
	MuscleReflex { target = gastroc delay = 0.020 C0 = 0.1 KF = 1 }
}

In this example, we add a constant excitation of 0.1 and an F+ reflex with a gain of 1.

  • Optimize the scenario (Ctrl + F5)

After a while, you will find that the controller adapts a toe-stepping gait.

  • by tgeijten