If you're training for a 5K road race, chances are you're doing plenty of distance and tempo runs. But although these workouts will get your slow-twitch muscle fibers into shape, you shouldn't forget about your intermediate- and fast-twitch muscle fibers—especially if you want to get faster.
Many runners don't realize that the 3.1-mile distance utilizes all three types of muscle fibers: slow-twitch, intermediate, and fast-twitch, says Pete Magill, the fastest American distance runner over age 50 in the 5K and 10K. Long workouts usually neglect the latter two.
"The gun goes for a 5K, and their bodies don't know what to do," he says. So in his new book, Build Your Running Body, Magill and co-authors Thomas Schwartz and Melissa Brayer propose a solution: short hill sprints, which instantly recruit all three types of muscle fibers and train the nervous system to use them together, rapidly and explosively. "If your muscle fibers were a basketball team, it's the difference between playing a game with no practice or lining up for the opening tip-off as a well-oiled machine."
In fact, Magill argues that just a single session of hill sprints can spark noticeable improvement in runners who've neglected their fast-twitch muscles. Case in point: former NCAA All-American track and cross-country star Andy DiConti. "He called me a few years back when he couldn't break 17:50 for 5K as a masters runner," Magilln says. "He'd been training all distance runs. I had him do one session of hill sprints, and he ran 16:20 in his race the next weekend." (That said, Magill admits that a half-dozen sessions spread over two to three months will provide the best training effect.)
To add hill sprints to your training regimen, start by finding a road that's steep, but not so steep you can't maintain a rough approximation of your normal stride. Warm up with at least 15 minutes of jogging, then follow this two-part routine:
Sprint up the hill at 95 percent of max effort, for 6 to 10 seconds. Do four to eight reps, depending on your experience and fitness level. Walk down the hill and take your time between reps, so your recovery periods are one to five minutes each.
Sprint down the hill at 85 to 95 percent of max effort. (Downhill's eccentric contractions further challenge you nervous system, Magill writes, and create protection against future quad soreness.) Run eight to 15 seconds, building into these reps more slowly than with uphill sprints and limiting your pace so you remain stable and in control. Do four to eight reps. Walk back up the hill and take your time between reps, so your recovery periods are one to five minutes each.
Ease into your initial downhill sessions, Magill cautions, because you're at higher risk for injury until your body adapts to this type of movement. Skip them completely if you're seriously out of shape, overweight, or have a history of lower-limb injuries.
Adding a 10-minute cool-down jog to the end of this routine can't hurt, he adds, but don't try to do more or combine these sessions with a distance run afterward. Don't jog between reps or short-change your recovery periods, either. "If you're jonesing for mileage, add a second easy run to the day's training."
Along with hill sprints, Magill also recommends "old-school intervals" and plyometric drills—exercises that include skipping, hopping, bounding, and depth jumps—for recruiting and activating fast-twitch fibers. Check out Build Your Running Body for his complete routine for retraining the nervous system, along with exercise photos, training plans, nutrition strategies, and more.