Pointer, I have nerve damage in my lower leg, and that affects strength and balance so I work the lower legs a lot. I think the best thing is hiking off-trail and at different angles, uphill, side-hilling both ways, downhill, etc., especially with a pack.
In the gym, I do a variation of skaters for side-to-side strength/stability. The variation is, don't stay in one place like you see in videos, jump a little forward each time. And don't be content to just hop a little, give it all you've got, concentrate on landing smoothly and holding the position for a second or two before you launch into the next jump.
Also, one-legged box jumps on a low box, concentrating on holding your position with a smooth landing.
For balance and stability, you can do a lot of different one-legged exercises on an unstable surface (BOSU ball or air cushion) or just on the floor. Start on the floor with a fairly heavy kettle bell or medicine ball in both hands at waist level, standing on one leg slightly bent. Bend down and touch the ball to the top of your foot, and push the off leg straight out behind you; then lift the ball and straighten up. Adjust the weight so you can do 10-15 reps at a time before your leg fatigues. Then work up to lifting the ball overhead with each rep (better balance needed), you'll probably have to drop down in weight for that.
Stand on one leg on the BOSU ball with the flat surface up. Have someone toss you a light medicine ball (not straight at you every time, they should knock you a little off-balance) for 60 seconds or until you can't any more. Do a few sets and your calves will be burning.
Stand on one leg on the BOSU, extend the off-leg straight out behind with your body as close to horizontal as possible, and do dumbell flies for your shoulders.
This one is guaranteed to burn your calves and works front-to-back stability and balance--stand on one leg on the BOSU and push your toe down until the front edge touches the floor; hold for a second then rotate your ankle backward until the back edge touches and hold for a second. Work up until you can do 20 at a time. You'll probably need a wet paper towel to wipe off the flat surface of the BOSU and the bottom of your shoe to keep from sliding around.
Last, this is another guaranteed to burn your calves. Jog backward on an inclined treadmill at 15%. I do this in 30-40 second intervals at about 3.6-3.8 mph, it doesn't take much speed to jog backward. After 30-40 seconds my calves are burning so I just turn around and walk forward at a slower speed to recover for two minutes, then go again. Best thing is, if you keep it up for 20-30 minutes you're getting both cardio and a calf-burning workout that is about as close as you can get in a gym to walking downhill.
