K2:
Seems like by the original post, and your last login date, you aren't checking this any longer. But... I though I'd toss in my two cents since the topic has resurrected, and it is a good question to consider if anyone else browsing the forum wonders as well.
First off: nice job on C2C! A buddy and I went on it in the 'later season' of 2014 - certainly one heck of a haul as far as day-hikes go.
Everyone has voiced some very great considerations, and I certainly agree with them too. Trail running is fantastic, the calf-raise suggestion is on-point as are the lunges and leg extensions. It sounds that you might be in the LA area and not passing through, in which case, the back side of Griffith Park is a fantastic training course. Run up and down the usually-quiet equestrian trails, and there's a few which criss-cross nicely for short and steep uphill elevation gain conditioning runs. When I used to live in the area it was my favorite area to train. And if you're feeling up for it, a run from Burbank to "the sign" and back is 12 miles - the uphill is fantastic (and great downhill conditioning!), a combination of fire roads and equestrian trails.
You do bring up something peculiar in your question though... pain behind the knee (hamstring area). If the pain was on the outer sides of the knees, that
could be an IT band strain. It won't hurt much at all on ascent, but its painful to step downward with any weight bearing. BUT, the crazy thing is that even though the pain manifests at your knees, the source lies at your hips. You'll ice and roll your knees all you want, but the pain won't let up. But instead heal and strengthen your hips, and the knee-area troubles go away entirely. Kind of wild how it manifests itself, but it can be frustrating and incapacitating for anyone - for weeks.
If this happens to be the case (IT band strain), some great exercises which I can suggest are:
- 2x20 one-legged hip thrusts (1x20 each leg)- 2x30 side-lying leg lefts (1x30 each leg) <- resistance using a Theraband around your ankles (I made a 2-foot-circumference loop)
- 2x30 side-lying clamshells (1x30 each leg) <- resistance using a Theraband just above the knees
Because of my own IT band propensity, I do a set of the above once every morning and night, regardless of being a rest-day or hike/climb/scramble day, just to keep the hips strong and everything in-check. Ever since, IT band issues and knee pain have not resurfaced. If you can't buy a Theraband specifically, the generic rubber stretch bands from Sports Authority et al work just the same.
However, aside from whether it's an IT band issue or not, some other great considerations for downhill, to support those by everyone else, are to consider trekking poles. They won't make a trek any easier, per se. They'll just re-distribute part of the load-bearing onto your upper body. Even if you don't need them for ascent, it's nice to have a pair (or at least one) on descent.
Another thing to consider specifically regarding training and fitness is to use free weights. Or rather, strike a balance between machines and free weights. The great thing about machines is they clinically isolate and focus specific muscles and muscle groups. But, I've learned this can also be a not so great thing. They offer limited 'functional' stress training on your body. Seated leg extension and leg press (or even bicep curls) only translate the muscle in 2 dimensions - while the other muscles of the body are suspended at rest: whether sitting in a chair, or legs/arms rested against a pad to control range of motion. The great thing about free weights though, is that when do the equivalent exercises, you are instead translating in 3 dimensions, much in the same way when you are hiking and such: the range of motion is larger, each 'rep' doesn't happen
exactly the same way each time, tendons and secondary/tertiary muscle groups and core become involved for balance and agility, and you are load bearing - even your own weight (for example, a triceps dip machine at 60-70 lbs versus doing tricep dips on bars suspending your own body weight). Doing a combination of machines and free weights strikes a great balance all the way around, in my opinion.
My overall understanding is that the hamstrings will take the most brunt, since we're often heel-striking on a downhill step with our leg full extended. Then the quads take it secondarily as we begin to bear weight on the leg and shift weight - rinse and repeat. Here are some great gym exercises to try adding for leg-strength, much of which will strengthen ability to handle downhill:
- Sled Push and Pull w/ weight (in place of leg extension and leg press machine) <- these are fantastic for cardio when done in sets, feels like HIIT stress on the lungs/heart for me
- Standing Calf Raise w/ dumbbells (in place of calf raise machine) <- great for balance strengthening too
- Straight-Legged Deadlift w/ kettlebell (in place of leg curl machine) <- I actually can't much use the machine version, it stresses my hamstrings in an unnatural position
- Lunges (as mentioned by others, with free weights as-needed)- Squats (as mentioned by others, with free weights as-needed) <- forcing my feet pressure to twist outward, but not actually twisting them, I find gives me a better stretch
- Reverse Step-Up w/ dumbbells- One-Legged Deadlift w/ dumbbells <- not particularly for knees, but good for hip and ankle stability to help thwart knee issues
Likely not best to do them all at once
Personally, I break these into 2 different gym routines.
Two other techniques to use when actually out trekking on really steep downhill are to use a combination of small-steps (shuffles) or a weaving path (weaving, as in, within a trail's boundary if there is a trail). The shuffling helps both keep the heavy load off of your legs on big downhill steps, it keeps your center of gravity nice a low from accelerating. Weaving gently back and forth can also aid in cushioning you from the stressful "STOMP!" of a steep downhill step drop - and again, arrest a downward acceleration. On very steep and loose-dirt slopes I've found a combo of the two to work quite well. These won't solve the downhill issues through training, but they are useful techniques for negotiating some downhill terrain.
But... maybe this will be of help too, along with everyone else's great ideas.