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;
	}
}

Well this may not help much but I’ve heard its more efficient to multiply by .5 than to / by
2