It is preferable to have actor strike a “T-pose” before the actual action. The software will need T-pose for building actor appearance model during tracking.
It is recommended to face the palms down, as it corresponds to the default orientation of the model's hand bones.
Sometimes it is inconvenient or not possible to stand in T-Pose. You can do without it, but in this case initial alignment of actor model in iPi Mocap Studio
will require more manual actions.