Really Sore

I am sore everywhere this morning. Yesterday in riflery, our teacher wanted us to try unsupported positions. So far, we had only done the prone supported (which means lying down with the rifle propped up on sandbags). However, now we are experimenting with all the unsupported positions, prone, kneeling, and standing. Unfortunately, the gun is more than half my height and 15 pounds and now is only being held up by one arm. Which is killing me. My neck is sore, my back is sore, both arms are sore and I can no longer reliably hit the target. At least my professors are sympathetic.