Originally Posted by Jan Ch
Hi, my friend and I summited Whitney 8/17, hiking for 18.5 hours on a day permit. It was grueling and we were both wondering to ourselves why people would ever want to do this hike

I've wondered that every time I've done it:-)

Sorry, I have little advice for your condition. Advil, stretching, and time will solve your problem. The "true" solution is better preparation. Like you, I've done in, and then suffered. But for me I have found that if I can meet these two conditions I will have no problems (either the day of the hike, or afterwards):
1. For my training program I must work up to 24 miles/week (minimum) You can do in one day what you normally do in 1 week of regular training.
2. On the longest day during the week I need to go 12 miles (minimum) You can do in one day double your biggest day of regular training.

I do as much climbing as possible, but that is normally only ~ 5K'/week, and only 2.5K' on my biggest day. I have not found that to be insufficient. More would naturally be better.

By the way: Congratulations on achieving your goal. It is not a simple task.