Hi,
I would get this done by deleting the animation (frames) of the Torso/Lleg/RLeg/LFoot/RFoot layer in the Motion Layer.
- Rightclick Motion layer > Sample Motion Clip > Sample All Parts - Optimized
- Click and drag (or CTRL and drag for selecting in multiple layers) in a layer you want to delete frames in (in this case: Torso/Lleg/RLeg/LFoot/RFoot) and press delete.
- Afterwards rightclick Motion layer > Flatten Motion Clip > Flatten All Parts.
You now have an animation layer without any motion below the torso.