As opposed to a therapeutic modality, weight training is something all athletes should do, regardless of what their chosen sport is. Personally, it took me a long time to be convinced that weights could do anything for distance runners, until Tom (my coach) talked me into giving it an honest try while not running for a few weeks, recovering from yet another overuse injury. So, I did some reading on circuit training, talked with Tom about the type of training that would benefit me the most (high reps, low weight), and gave it a try.
I am convinced that weight machines are the only way to go for newcomers to weightlifting. They allow you to adjust the weights very exactly, without hauling around a bunch of heavy weights which you can not put on tightly enough so that they fall on your foot; they're also considerably safer than free weights, since it's almost impossible to drop a weight on yourself. Also, the stations on each machine are set up so that the exercise to be done there is fairly obvious.
In general, there are one of two goals that people have when starting a weight training program. They either want to add muscle mass and gain weight ("bulking up") or want to gain endurance and muscular definition. Unless you're interested in competing in bodybuilding, or want your body to look more "ripped", there's no good reason to want to gain muscle mass. One good reason for this is that few weight lifters incorporate any aerobic conditioning into their program, with the result that the muscle being added has an insufficient blood supply. This can result in poor endurance, high blood pressure, and other nasty health consequences. (I was discussing this issue with a weight lifter, who assured me that he did regular aerobic training. "Yeah, I go out and ride my bike for 3-5 miles every other day after my workout." Scary.)
If you're a runner, biker, or other endurance athlete, you'll be amazed at how quickly some weight work will start to pay off. And, it's not subtle! After about six weeks of weights, I was out doing 440yd hill intervals, and suddenly realized that I was using my arms to help me move up the hill, and they weren't getting tired! In fact, I was definitely going up the hill faster than before (as usual, I wasn't timing the intervals). On the way back to the gym from the hill, I focused on my upper body and how it felt, and it was clear that my arms and shoulders weren't just along for the ride - they were moving harmoniously with the rest of my body, not really pulling me along, but giving me a very balanced feel.
The actual weight workout I did was nothing special....I did about 20-30 minutes, every other day, after the day's run. I pretty much stuck to one all-purpose machine, concentrating on my arms, chest, back, and anterior leg muscles. Remember, runners have very well developed posterior musculature, since they're used in pushing you forward; however, the muscles in front are comparatively weak and unbalanced. That's why so many injuries are caused by weak anterior muscles - shin splints (tibialis anterior), iliotibial band syndrome (tensor fasciae latae), and several knee problems (quadriceps).