Many widely available half-marathon training methods include only running. Others include cross-training--bicycling, swimming, walking, or cross-country skiing--that make similar cardio demands to that of running. Strength training could pay better dividends on the time you put in.
CrossFit Coach Dave Werner of CrossFit Seattle, asked what he would do with aspiring half-marathon runners who want to run faster, says he'd have them run three days a week: (1) run intervals at your intended race pace; (2) run shorter intervals at a significantly faster pace; (3) run "long slow distance," a significantly longer distance at a slower pace than you intend for the race.
Dave also recommends strength training. For people interested in coming to CrossFit Seattle while training for a long run, he says, "we would lay a foundation of basic strength movements--deadlift, squat, military press, pull-up, push-up or dips. And we would spend some time doing high-power-output intervals, like wallball or kettlebell swings: basic hard work. For most working adults, a three-day-per week running program is pretty effective. If you add to that two or three days of complementary strength and work, that's a great program." CrossFit is strength and "hard work" combined. It doesn't take all that long each session, so a program of three runs a week plus CrossFit (emphasizing strength) could let you spend less time training.
Why does a runner need to be so strong? Most runners don't want to haul extra weight on a long run, even if it's muscle. But in ten or twelve weeks of strength training combined with running, any muscle weight you add will be muscle mass that you needed; you won't add bulk through running plus CrossFit. "It takes strength to interact properly with the ground," Dave says. "The midline stabilization you get from movements such as the deadlift help you run better--better able to power up hills, sprint past competitors, and run more efficiently. And maintaining some upper body strength also just helps keep you healthy. The whole body works better when the core works right."
Beginning CrossFitters often lose fat and gain some muscle, ending up weighing about the same and being stronger. For distance runners, then, CrossFit combines the benefits of strength training with those of traditional cardio cross-training: it builds the strength to run faster, longer, and more efficiently; and it mixes up your movements to help prevent overuse injury from running.
CrossFit Endurance wants CrossFitters who like endurance sports to do standard workouts three days on, one off, plus CrossFit Endurance's suggested endurance workouts. They say this will let you spend less time training and still get better endurance results. Their FAQ offers a good explanation and thought-provoking discussion of the benefits and drawbacks of aerobic vs. anaerobic training.
Looking for non-CrossFit sources who believe in strength training for runners, I found an experienced running coach and an appealing egghead.
Doug Lentz ,C.S.C.S., is a former triathlete turned cyclist, as well as a competitive Olympic-style weightlifter. He trains athletes in 14 sports and finds that as few as six weeks of weight training can reduce or eliminate problems in running such as kneecap pain, hip pain, and low-back pain. Weight training also contributes to better performance by allowing the body to use oxygen more efficiently. Additionally, being stronger increases a runner's time to exhaustion. Lentz recommends weight training two to three times a week in season. (Here's more about fixing back pain.)
Writer and longtime runner Richard Gibbens makes it his job to review original research on endurance training and report what he finds. Gibbens concludes that strength training improves running performance, especially in novices, because of what he calls muscle power: an increase in "three muscle factors: strength, max contraction speed, and resistance to fatigue." Resistance to fatigue is, he says, the most important factor in improved long-distance performance that is due to strength training. Read the article for more details and for Gibbens's definition of strength training. He recommends strength training one to two times per week during running training.
Gibbens reviewed studies of runners' rates of injury as well, and reports, "It's no secret - runners suffer a high incidence of injury.... Increasing weekly run mileage is associated with a rapidly increasing incidence of injury." Before devoting themselves to a program that involves dramatically increased mileage, runners should be aware of the risk and should consider a training method that involves conservative mileage increases and more cross-training for strength. Read the article.
Squeeze some CrossFit workouts and old-school strength training into your running program and see your results improve thanks to strength.