In my opinion, you shouldn't be single handing offshore in heavy weather unless you are in similar shape as a navy seal or CG rescue swimmer, or close to it. Precisely for the reason that when bad situations happen you only have YOUR OWN strength, stamina, knowledge, and resourcefulness to rely on.
Damn, guess that disqualifies me from any further ventures offshore, then... (grin)
Ahh, well - I try to make up for my physical limitations by sailing an appropriately-sized boat... (except when I'm being paid to do otherwise, that is)
BTW, I originally got this trailing line technique from one of Hal Roth's books, the dude who's got salt running through his veins and gnarliness growing in his back hairs!
Sadly, for Hal, that would be "used to
have salt running through his veins..."
I've had the distinct pleasure and great honor to have met Hal and Margaret, although it was somewhat awkward, as the top of his head drew about even with my chest (grin) While still appearing quite fit, he still looked a few decades removed from having ever met the physical requirements you outline above for sailing offshore...
Of course, I certainly agree with your basic premise. Physical fitness is a hugely important aspect of sailing offshore... I'm simply appalled at the extent to which I see so many Mom & Pop cruisers "over-boated" today, out there in boats WAY beyond their ability to deal with when the breeze comes up, and things like electric winches or windlasses start crapping out... Lots of folks out there, rolling the dice in that regard, bigtime...
Many today could do well to take a cue from Hal and Margaret, who never cruised in anything larger than 35', if memory serves...