Ponzy: If you can increase your loops so that you can do 16-20 miles in one day, then you will do pretty well on Whitney. The one thing you might consider in addition, is spending two nights at Horseshoe Meadows before Whitney to get yourself better acclimated to the altitude. Please understand: You are starting the Whitney hike at the elevation of the top of Half Dome. Altitude is a big factor on Whitney, and not at all on HD.
Steve is absolutely right. I wouldn't touch Whitney without a couple of 15+ milers under the belt in the two months leading up to Whitney.
If nothing else that should limit your challenges to naught but the altitude, but even that can be helped.
If you are able, try small runs throughout the week. If nothing else, running increases your cardiovascular efficiency along with pacing your breathing.
My policy @ altitude is three-fold:
1: Respiration up and heart-rate down.
2: Decisive use of NSAID's. I don't like the idea of Diamox simply because it is a diuretic and you lose a lot of fluid already, so I use Ibu to combat the headache. Of my three-pronged stratagem this is the only one wouldn't necessarily "recommend."
3: Keep Hydrated and fueled at any cost. Altitude is an insidious malefactor. During hikes your muscles and brain are constantly leeching
water, nutrients, and oxygen. Digestion, coincidentally, also requires a large amount of oxygen to occur. At altitude what little oxygen is present (At 14,000 feet there is 50% of the oxygen present at sea-level) is prioritized to the brain and muscles. In response you begin to feel weak as the nutrients in your body get depleted, but your digestion system triggers nausea because your digestion system is slowing down due to the lack of oxygen. So altitude lays siege to your body as your oxygen is limited and your desire to take in nutrients plummets.
I make sure that I'm forcing down whatever food I can. I also use a combination of cytomax and whey protein to keep a steady stream of macronutrients (lipids, carbs, proteins). Having those calories to drink makes 'em easier to stomach.
Honesty time... I'll practicing singing when I'm alone and on trail it strengthens the diapraghm
