Run holding a full to the brim cup of McDonalds Coffee. Don't drink it, just run with it. I guess water would work too, but there is no consequence for spilling water on your hand.
Actually holding still is not so much a matter of strength as it is a matter of relaxation. A school principal I used to work for was also a top notch long range marksman, in whatever category uses a rifle without a scope and from a standing position. He professed relaxation, breathing, and a calm focus. If I get into a rifle-holding stance, and relax my shoulders a lot, I can handhold up to 80mm on a 35mm down to 1/25 pretty darn consistently. My MF camera is awkward to handhold and I am not as consistent but I think the weight helps sometimes. But, I would rather use a tripod.
Technological society has succeeded in multiplying the opportunities for pleasure, but it has great difficulty in generating joy. Pope Paul VI
So, I think the "greats" were true to their visions, once their visions no longer sucked. Ralph Barker 12/2004
Quit drinking whiskey, ........................
This is incorrect unless you do not like whiskey.
Always carry at least one half pint of your favorite 80 Proof and consume as needed until you achieve success at those attempts at 1/4 and 1/2 second rigid catatonic states.
You might look into the techniques that competition target shooters (espcially pistol shooters) use, as they have a similar need to hold stready.
"It's hard to hold steady when half your friends are dead already."
Sorrry, couldn't resist the quote from one of my favorite bands...
The breathing out thing works for me. Also, if you have a fancy SLR w/ motor drive, try taking 2 photos with continuous drive. The second photo might not have as much shake since you're not punching the release.
Standard technique since the dawn of (photographic) time has been:
Breathe in slowly, breathe out slowly, hold your breath for one second (no more, you'll become self-conscious and make things worse) and squeeze the release gently but firmly in a continuous motion (obviously jabbing the release will give camera shake, no matter what else you do).
Cut down on American coffee (ground variety). This weekend past, I went to a village scarecrow competition close to where I live. People had built amazing scarecrows outside their houses.Great photo opportunities. The whole village was a kind of "open house" and at one house a genuine Texas lady was serving genuine Texas coffee. Very nice but very strong. I was super alert after one cup, would have defended the Alamo after two and chased the Mexicans back across the Rio Grande after three and been banned from competing in the Tour de France for life!
If I drank as much coffee as I do tea and I don't do that excessively, I'd be seriously "twitchy".
I still use the method I learned to fire a rifle as a young marine recruit more than forty years ago, to control your breathing, and take first pressure on the trigger ( taking up the slack) or shutter release then gently squeeze.
I use a cable release whenever I think finger impulse might be an issue. My nuttiest experiment was to push on a long bulb release with my foot. It works well, but it's not cool looking. Better to use a timer
Regarding breathing, I do personally find that my hand action is best while I slowly exhale. Holding my breath doesn't help one iota, for me personally!