rotating a bone slows down frame rate considerably

I have an update loop that slows down considerably --going from 30fps to about 9 if I add the lines below that are commented out. The project moves a character's feet depending on the mouse position.

Is there anything inherently slow about any of the commented lines?

 if(sidestep==true){
     if(boneY.name==hip || boneY.name==leftthigh){
         return;
     }
     else{
 
 var steprotation=.1*((mousevec.x-Screen.width/2)/(Screen.width/2));
 var steprotation2=.1*((mousevec.x-Screen.width/2)/(Screen.width/2));
 //hipgo.transform.rotation.z=steprotation;
 //leftthighgo.transform.rotation.z=-steprotation2;
 //leftfootgo.transform.rotation.z=steprotation2*.1;
 //rightthighgo.transform.rotation.z=steprotation2;
 //rightfootgo.transform.rotation.z=-steprotation2*.1;
     }
 }