[RiverEco]

Two questions

(1) Which muscles do you use when you are casting a fly rod? Is it your tricep and bicep pushing and pulling your forearm? Is it your forearm muscles flicking your wrist? This seems unlikely as I am often reading that you do not use your wrist when casting. Or is it the rotation of your shoulder-this does not make sense either as you rod would move on a wildly convex arch.

(2) Is it the weight of the fly line and associated resistance that bends and loads the rod?

I can sometimes feel the ideal cast, but I cannot pin down these factors. Thanks for any insight

[nu2trout]

After you cast all day where do you feel sore? That would be a good place to start deciding which ones you use.
I am no certified caster nor am I ATC (certified trainer) but I think I can help you a bit.

As I am learning more about the proper casting techniques I am finding the following, in regards to your question;

forearm strength to keep a good grip and keep control of your wrist
bicep to pull the rod to you for the back cast
tricep to push the rod away from you on the forward cast

shoulder muscles to keep control of your arm and allow for the slightly upward rotation of the arm, and downward rotation on the forward cast.

You may notice some discomfort deep in your shoulder after a long day of casting and those little guys would be your rotator cuff, all four of the little muscles surrounding your shoulder.
The more you cast the stronger they will get, but do not keep casting or throwing once they start burning and letting you know they need a break. Give them a break and let them build up, remember they are small muscles and you do not want to miss fishing time because of a surgery on them.

Again, I am not a doctor or certified caster but I did sleep in a Holiday Inn Express last night. I hope this helps

[RiverEco]

Excellent response - that was the type of information I was hoping to receive! I read that your hand needs to be on a level horizontal plane during the front and backward casting stroke. Is this true, or does your hand move on a slight arc (down on the forward casts and up on the backward cast)?

I watch people cast and see their rod carve a small wedge in the air during their casting stroke, and wonder how that can be if your hand stays on a single plane.

[Peddler]

Your casting stroke works best if the forward and back cast are on the same plane. That 180 degrees can be tipped so the forward cast is aimed high or low but the back cast, for the most part, should tip so it in at the opposing angle.

[nu2trout]

go to sexyloops and search around. those guys do some good video of the arm in action, and they are serious casters. that should give you the visual you are needing.

[RiverEco]

Thanks for the info!