another technique to make the ups easier, esp steeper, trail breaking...
the 'rest step', you can look it up n shit, but in a nutshell:
instead of moving with a smooth continuous gait, you power up your leg extension and lock your knee on whats now your back leg, swinging your other foot fwd into place
pause for whatever you need, a half second relaxation goes a long way, or if your breaking a steep technical track you might need say 5 - 10 secs to stamp in your next ski length with your front foot. the part that counts is that your weight is on your back foot, and your knee is locked so your bones take the weight and your muscles can rest.
repeat x 5000 or whatever