My vote for most fatiguing (I'm including mental fatigue (getting bored) as well as physical exertion) style of fishing would be:

1st) Streamer fishing (more cast and you need to strip all they way in to cover the water)
2nd) Lure Spin Fishing (less cast than streamer fishing but you have to reel the lure all the way in before you recast ...forearm burning after two hours of fishing in strong current)
3rd) Dry Fly fishing ( more false cast but usually with a lighter rod and one weightless fly the downside is that I get bored unless there is a major hatch/rise going on)
4th) Nymph fishing..my default fishing setting..(it's very stimulating for me mentally which makes up for fishing a slightly heavier rig..2 or 3 flies, indicator and split shots.)

So in my opinion I could be content and fish a nymph rig all day with much less fatigue that if I were forced to fish a different way all day..most of those styles I would have given up on and switched to nymphing after about 2 hours..