This is a training technique used to see if the student is recoil anticipatory.
Unbeknown to the student the instructor loads every other chamber of a revolver and leaves every other chamber empty (or loads every other round a dummy round in a semi-auto magazine) and observes if the trainee jerks their hand when firing on the empty round.
If it’s determined the student is flinching in anticipation of recoil the training can be tweeked to correct it.
That’s what I was going to suggest. Have a friend load half the cylinders in a random pattern, leaving the other half empty. Most people have some flinch, but someone who flinches a lot will jerk the entire revolver even when “shooting” an empty cylinder. As suggested, you can do the same thing with snap caps in a semi-auto pistol, but it’s easier with a revolver.
Dry firing with a pistol equipped with a laser sight is also useful. Hold the pistol and squeeze the trigger, trying to not move the laser image on the wall or target. Make sure the gun is unloaded or loaded with snap caps.
It’s called “flinch” and even top marksmen struggle with it from time to time. It’s purely psychological and it’s due to the anticipation of the shot, both recoil and noise. If someone were to push you gently without warning, you would sway back in a relaxed manner, but if he tells you he’s going to push you, it’s very hard not to brace in anticipation. Different people react differently but it’s usually either up or down. Remedies include:
Random dummy round mentioned above (this will reveal flinching but doesn’t cure it)
Switching to a small caliber like .22lr for a while and mastering the flinch there.
Change the way you think about it. You are reacting to something that is “done to you”. Try to internalize the shot You don’t flinch when you throw a punch or yell. Take it over and make it part of what you are doing.
I agree with the recommendation on moderate strength training which is a good thing to do anyway. I would add to that some grip training. Grip strength is the most useful all around strength, in my experience. It pays off even for activities that require dexterity. Strength is a crucial element in control. Not the only factor but crucial. If your muscles are working near their limit, your control will be poor. If you have strength to spare, they will do whatever you need.