I agree with Bulldog here. I've trained by biking and felt my quads burn so much more than hiking, but when it was time to throw on a pack and hit the Sierra or anywhere else for an extended period of time, I lose my mojo much faster than when I trained by going up local mountains, no matter how small they may be. I'm not a physical trainer or have a degree in human health, but I assume the bike can never prepare you for the strain on your knees and ankles. You're also working different muscles. Even snow shoeing versus regular boots had different parts of my legs hurting.
My regimen is not fixed, and I basically do what I feel like on any given day. It usually involves 5 hikes a week at one of the local mountains. They'll be 3-12 mile hikes with approximately 800-3,900 ft of gain. At least one of those hikes will be with a pack; 25-100 lbs depending on the length and elevation gain of the hike.
At least once a month, I'll go out to something bigger in the San Gorgonio, Jacinto, or Baldy area. I try to do a loop like Marion, Jean, San Jacinto or San Jacinto to Cornell. Mix and match them so I won't get bored doing the same trail over and over again.
No weights, just pullups. I throw in a bike ride every now and then. 2-3 miles before or after a hike, or I do about 12 miles as a stand alone.
I would be more healthy, but I eat junk food like there's no tomorrow. Carne asada burritos and Wiener Schnitzel chili cheese fries all day...and yes, I have high blood pressure and cholesterol but I don't care, they taste too damn good! I'll never be Ueli Steck, and out there to enjoy the wilderness and excitement of the mild scrambles and Class 3 stuff (and rarely a touch of 4), and the incomparable views. The training is enough to get me up and back safely, but I do get passed like I was standing still by quite a few (alright a lot) of folks up there.
I think anyone who does what I do can get up Whitney and back as a dayhike with a smile on his or her face. The key for me is to vary your trails and work out (hike 3 miles, jog 2 or hike 6 with a pack, or hike 3 with a pack then bike). Do something different so your muscles don't get used to one routine, and more importantly, so you won't get bored.
I've never stepped into a gym and never will.
Hike, hike, hike. I always figured the best training for hiking uphill with a pack was, well . . . hiking uphill with a pack. Call me crazy.
I'm fortunate in that I have a decently rugged mountain about 15 minutes from home (Kennesaw Mountain National Battlefield Park), and my wife and I try to hit it twice a week. Sometimes catpappy joins in, but since he's been recovering from a severe ankle sprain in July, not so much lately. Our typical workout is a 6-mile OAB route with 15-pound packs, getting about 1800 feet of gain. We mostly keep it under two hours, but occassionally it's over. Prior to our Sierra trip this past summer, we were hitting it in 1:35 with 15-pound packs and still less than 2 hours with 30-pound packs.
I'm 54 and my wife is 45, so this twice-a-week regimen works pretty well for us. About 8-weeks prior to our annual summer Sierra trip, we kick the pack weight up to the low thirties and try to hit it 3 times a week. I've been tracking the details of my hikes for about 5 years now (distance, elevation gain, time), and I've found that those years when I can get at least 200 miles and 50,000 feet of gain in, Whitney (and other peaks) come pretty easily. Before heading for the Sierra this past July, I had already logged 280 miles and 65,000 feet of gain for the year, and I felt pretty fresh on both Whitney and Mt. Dana, and so did my wife.
I've gotten more into technical rock climbing this year, so I also do some upper body and core work for that, in addition to the occassional trip to the climbing gym, but I'm a firm believer that if you want to hike up big mountains successfully, the primary thing to focus on in training is simulating that activity as much as possible.
