Weighted lunges and squats. Sounds like cardio isn't your issue, it's muscle exhaustion, so you need to build up your muscle stamina.
Beyond that, make sure that you are stretching plenty before, during and after each hike or workout.
You also might want to try taking a magnesium supplement before your next hike to see if that makes a difference.
i can squat 220lbs max. I can squat 135lbs for about 12 reps. Bodyweight squats i can do probably 30 or maybe even more. never really tried past 20.
What kind of rep range do you recommend? I thought the stair climber at the gym would improve the leg stamina as i tend to do about 100 floors at a time, but i hate to admit it really hasn't.