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Run Your Fastest 5K

An all-encompassing guide on nailing the 5K from building the speed and strength of a miler to increasing the endurance of a marathoner.

Legendary Australian running coach Percy Cerutty once said, “You only grow as a human being if you’re outside your comfort zone.” That’s 5K training in a nutshell. Because to master the 5K, you can’t just run distance, goal-pace intervals and a tempo run or two. Instead, you’ll have to schedule workouts that target every aspect of running fitness.

A fast 5K requires the speed and strength of a miler combined with the endurance of a marathoner. You can achieve that by performing a wide variety of fast-paced workouts—some that will certainly take you outside your comfort zone. The result will be an upgrade in your all-around running fitness and, quite possibly, a new personal record (PR). Over the following pages we’ll dissect each piece of the preparation process and explain how it all comes together on the way to your fastest 5K.

Speed and Stride Mechanics

“I’m afraid of the 5K,” confessed Laura, an experienced marathoner who’d asked me to coach her at shorter distances. “In the marathon, I have time to get my rhythm, but the 5K is like getting shot out of a cannon.” It’s true that the 5K requires quickly accelerating to a pace that is 30–60 seconds per mile faster than the marathon. But it’s also true that improving your acceleration and your ability to run comfortably at 5K pace are easy fixes.

Slow-twitch muscle fibers are associated with endurance, while faster fibers (both intermediate fast-twitch and fast-twitch) give you strength and speed. On distance runs, you rely almost exclusively upon slow-twitch fibers. Even at marathon or half marathon pace, you use very few faster fibers. But when you accelerate off the starting line of a 5K, you use all your muscle fibers—and keep using most of them throughout the race. To use those fibers effectively, you’ll have to properly train them.

Once a week—twice if you have time—perform a short bodyweight or free-weight resistance-training routine. These exercises force your nervous system to recruit all your muscle fibers both simultaneously and explosively, mimicking the demands of the 5K start. This isn’t about building bigger muscles. It’s about teaching your body efficient control of your muscle fibers. Click here for a detailed resistance training routine.


“I can hold my goal 5K pace for a mile or so,” says Leonard, a masters runner hoping to turn back the clock, “but then I fall apart.” Leonard’s training included distance runs, tempo workouts and 400-meter repetitions at his goal race pace. “I’m covering all the bases,” he says. Except that he wasn’t. Leonard wasn’t training his intermediate
fast-twitch fibers, the very fibers that are key to maintaining 5K pace during a race. Intermediate fibers are crucial because they can be trained to provide both the strength and speed of fast-twitch fibers and the endurance of slow-twitch fibers. This allows you to run faster for a longer period of time. But achieving this transformation requires workouts that specifically target intermediate fibers.

3K-Pace Repetitions

Once you accelerate to 5K pace, you’ll need a relaxed stride to maintain it. Since no one can relax when a pace feels “fast,” you’ll want to include some faster-than-5K training. Workouts at 3K pace—or about 15 seconds per mile faster than 5K pace—will make “slowing down” to 5K pace a breeze. Examples include 200- and 400-meter repetitions at 3K pace with at least a 1:1 work-rest ratio between repetitions.

5K- or 10K-Pace Repetitions

Running repetitions at 5K and 10K pace forces your intermediate fibers to produce aerobic energy (the energy source that fuels endurance) at near-maximum levels. A sustained effort at these paces triggers these fibers to physically change in order to produce even more aerobic energy in the future, thus improving your endurance. The catch: It takes two minutes to reach the critical level of aerobic energy production. So, you’ll have to build up doing a series of repetitions in training that last two minutes or longer, e.g., 6 x 800m @ 5K pace, 5 x 1000m at 5K pace, or 5 x 1 mile @ 10K pace, with about a 2:1 work-rest ratio between repetitions. These types of repetitions will also help you improve your running economy, the equivalent to a car’s gas mileage. The goal is to run longer and faster than someone else while using the same amount of oxygen. All of the workouts we’re covering in this article build economy, but for 5K-specific economy you’ll want to include some track repetitions at 5K pace, such as those just described.

Hill Repeats

The force required to run uphill immediately recruits your intermediate fibers, creating an energy demand in those fibers that far exceeds what aerobic energy can provide (anaerobic energy, which doesn’t require oxygen, picks up the slack). The result is that hill repeats at 3K effort—not pace, as the grade of the hill will slow you down—lasting 30–90 seconds trigger two physical changes in these fibers: better strength and increased aerobic energy production. The recovery interval between hill repeats is important. It should last two to three times the duration of the repetition, e.g. 60–90-second recovery for 30-second hill repetitions.


Of course, the training benefits we’ve discussed are meaningless without a strong endurance foundation for your slow-twitch fibers. You’ll use 100 percent of these fibers continuously during a 5K, so you need them to be both strong and capable of producing oodles of aerobic energy.

Tempo Runs and Tempo Intervals

Just as running faster repetitions at 5K and 10K pace builds aerobic endurance for your intermediate fibers, tempo work does the same for your slow-twitch fibers. “Tempo” is run at an effort that is roughly equivalent to your half marathon or marathon pace. Continuous tempo runs last 20–30 minutes. But I prefer to break them into 10-minute repetitions with three-minute jog recoveries—that way, you can adjust the pace if it’s too hard.

Distance Runs

Distance runs of 30–60 minutes at an easy pace strengthen your heart, increase fuel supplies within your muscles, and fortify your muscle fibers and connective tissue (bones, tendons, and fascia). A long run every week of 90 minutes or so will also help boost your aerobic energy production.

Brain Training

The final hurdle to clear isn’t found on the road or in your muscles. It’s your brain. Your brain is hardwired to prevent you from damaging your body with a dangerous effort. Therefore, you have to teach it that 5K races are safe. The easiest way to do that? Race a 5K! Many runners find that their second 5K is surprisingly easier and faster than their first, and the reason is largely because you know what to expect. Having felt the discomfort and anxiety that comes with running a 5K hard makes it slightly easier to run another one, as that familiarity (and continued training, of course) breeds confidence to continue pushing outside your comfort zone. As your training progresses and after you’ve raced a few 5Ks, you’ll acquire the ability to really attack the race, and that’s when your PR will really start to fall.