Figure out how you are doing things now, cause that ain't working.
You have to know where to start...
I have been shot twice, blown up twice, three aircraft crashes in the military, and broke a bunch of stuff racing, working, etc.
Believe me when I say, 'SUPPORTING, Comfortable Chair with feet flat on the floor',
And the press lifted up where you can see/reach the shell plate without stopping over...
The second thing is don't confuse bruised muscles/tendons from doing something new with outright tendinitis.
Sore, slightly inflamed tendons let you know about it, outright fully swollen tendons won't let you sleep or move your body.
So called 'Ergo' handles don't work for me very well or very often...
They cause 'Roller Wrist' or 'Limp Wrist' issues when sizing to start with,
They also are ALWAYS cut to to the wrong angle so follow through has my hand/wrist at an odd angle.
I like a 'Ball' handle, something I can put significant pressure on it at the TOP of the stroke, and the BOTTOM of the stroke,
Ergos are made to make the CENTER of the stroke more comfortable, which is a ONE finger operation for me since the case is free of dies.
With a ball I can adjust my position in the chair, adjust my shoulder to the press, etc and still apply pressure where it counts.
I don't use a 'Swivel' or 'Roller' chair.
You won't notice it, but you are expending MUCH more movement fighting the movement of the chair when you are working.
Nothing like fighting stiff brass, fighting the chair AND the press too low...
Leaning over to push down to size is direct pressure on shoulder/elbow with your body weight...
I like the Up stroke about an inch below my shoulder where I'm reaching straight out, without reaching up.
Keeps me from pranging on a bad rotator cuff and torquing on bad neck disks.