Congrats on your summit success!
I day hike Whitney annually and my training involves running 3 times a week and then doing practice hikes every other week leading up to the Whitney hike. I'll start out doing a hike or two in the Bay Area where I live, and then head to either Yosemite or Kings Canyon to do longer hikes in altitude that roughly simulate the distance and vertical gain. That way I arrive at the trailhead with some confidence. The altitude affects me a great deal and is what makes Whitney so difficult, but I always suffer through it the best I can. I don't take Diamox or equivalent but I do acclimate a little by spending a night or two at either Horseshoe or the Portal.
Partly to make the upper sections of Whitney more tolerable (and perhaps even enjoyable like in the good old days) and partly because it's another challenge, I plan to do something different this year. A 3 day loop hike starting at Kings Canyon, going over 3 passes (Avalanche, Colby and Forester) only a week and a half before the Whitney day hike. If that makes Whitney "more fun", then I plan to do it annually as well, and give me confidence that even at 58 I have many more Whitney years in me.
