Speed work is a popular type of running workout, but many runners avoid it. Whether you’re training for a 5K or a marathon, speed work is essential to becoming a faster and stronger runner. Today I want to talk about exactly why runners need to do speed work, and share my favorite speed workouts for you to try.

What exactly does the term speed work mean? Although some coaches and runners use it to describe a run done at faster than an easy pace, I prefer to distinguish it from marathon pace (aerobic threshold) and lactate/anaerobic threshold runs (runs done at a moderately hard effort—such as 3-mile tempo runs), which serve a different physiological purpose.

Speed work refers to a type of running workout in which you are running for certain intervals near, at, or even faster than your VO2max pace. Your VO2max is a measure of how much oxygen your body can use; most runners will hit their VO2max pace around their 5K to 3K (2-mile) pace.

Why All Runners Should be Doing Speed Work

Myths about Speed Work

Myth #1: You need to be fast to do speed work.

No, you don’t need to be knocking out 5-minute miles in order to do mile repeats. Every runner can benefit from speed work. In fact, even if running faster is not one of your goals, speed work should still be a part of a well-rounded training program.

Speed work is performed relative to your running fitness and pace. Effort is what your body knows—not what someone else is running! Speed work is performed at an effort that hard for you, whether hard is a 6:00 minute mile or a 10:00 minute mile.

Myth #2: You must do speed work on a track.

The track can be a great place to do speed work: the distances are measured, you don’t have to stop for traffic, and the surface is smooth and flat.

While there’s nothing wrong with doing shorter speed workouts on the track, doing your speed work on the roads or a paved trail offers numerous benefits. The varying terrain mimics what you will encounter on race day, especially if you are racing a 5K or 10K on the roads. Some runners experience IT band issues from running circles around the track, so speed work on the roads may also decrease your risk of injury. Bonus: you can use Runkeeper’s custom workouts feature to get audio cues for your interval workouts. No measuring needed!

Why Runners Need to Do Speed Work

How exactly do speed intervals make you faster? During speed training, you maximally activate your slow-twitch muscles and intermediate muscle fibers, which increases your aerobic capacity. Your aerobic capacity is essential to running any distance, whether it’s a mile or a marathon.

Speed work also increases your production of myoglobin, which is a protein found in your muscles. Myoglobin transports oxygen to the mitochondria in your muscles, which in turn produce ATP to give your muscles energy. So, as you increase your myoglobin, you improve your body’s ability to quickly transport oxygen to the muscles for energy, making you able to run faster. Speed work is uniquely beneficial in this aspect, as research indicates that high-intensity running is the best way to develop myoglobin.

Finally, speed work will help you adapt your body to store more glycogen. This is one of the reasons half and full marathoners should not neglect interval runs, since glycogen storage is essential to long distance running. Glycogen is the form in which your muscles store carbohydrates for easy energy conversion. The larger these stores, the longer you can keep running before hitting the wall. Speed work rapidly depletes your glycogen stores, thus sending signals to your muscles that they need to adapt to store more carbs for energy on future runs.

Even marathoners need to do speed work because speed work develops your fast-twitch muscles. While these muscles are dominantly used in shorter, faster races such as the 5K, when your slow-twitch muscles fatigue during a marathon your body will recruit your fast-twitch muscles. Training your fast-twitch muscles improves your running economy and your ability to keep running when you get tired—both very important for any race distance.

When to Do Speed Work

I recommend doing speed work no matter what race goal you have. Depending on the distance you are racing and how many weeks you have left in training, the frequency, volume, and type of speed work will vary.

Runners focusing on the 5K through 10K should include one quality speed workout at their race pace or faster per week. The closer you get to the race, the harder your speed workouts will become.

Many runners training for the marathon or half marathon will benefit from a brief speed segment in the first four to six weeks of your 12-20 week training plan. These workouts will transition you safely from base building to race-specific training, improve your turnover (the number of steps you take per minute) and form, and inject a bit of speed into your legs. I like to include short repeats at 5K-3K pace (hard to very-hard effort) during this phase.

As your training becomes more race specific, speed work for marathoners and half marathoners takes on a less important role. Instead, you focus on marathon or half-marathon paced workouts and long runs. Strides or a short set of add-on intervals after a tempo run provide all of the speed work you need in the final weeks before a long distance race.

When NOT to Do Speed Work:

Many runners want skip right over the base-building period, but this time is essential for improving each year without burning out. The base-building period occurs during the off-season (when you’re not training for a particular goal race – usually winter or summer). The focus of base building is to improve your aerobic fitness (build your aerobic base—hence the name) while giving your body a bit of a break from the hard workouts of race training.

I encourage runners to devote at least one month, preferably two to three, per year to base building. This is best done after you recover from your goal race. For most runners, the base-building period will occur in late fall through winter, which is ideal. No one wants to be doing speed work out in the cold or while confined to a treadmill!

You particularly want to avoid speed work in the two to four weeks after a goal race. Speed work stresses the body in order to produce the physiological changes necessary for running faster. In the weeks after a race, your goal should be recovery. In order to recover well, you must reduce stress—and that includes speed work.

My Favorite Speed Workouts

1. Countdown Fartlek

This countdown fartlek is one of the most popular workouts that I’ve shared on my blog. I like to start out at a moderately hard pace for the first and longest intervals and then gradually get faster with each one.

Short Fartlek Countdown Running Workout

2. Mile Repeats

Mile repeats are beneficial no matter what distance you are training for—they’re the ultimate customizable speed workout. You can do fewer repeats at a faster pace (such as 3 x 1 mile at 5K pace) or more repeats at a slower pace (such as 6 x 1 mile at half marathon pace).

My favorite is mile repeats at 10K pace. They’re challenging but not too tiring. I prefer these for later in a marathon or half marathon training cycle to inject some speed in the legs without detracting from the more race-specific workouts.