Which case do we need to use mucles?

Hi guys,

Based on available tutorials of LifeMOD, I get confused about some tutorials. Hence, I have some questions and I hope you guys can help me to answer them.

1. Why did tutorials such as bed setting, car crash, dancing, walking, fighting so on remove muscle set during building the model and not take these muscles into account?

2. How can we know which case we need to include the muslces and which case is not?

3. Can we apply external forces to some component of the human body and run inverse dynamic simulation which is used to "train" the muscle set?

Thank you in advance for your help!

KIM THO