Why Runners Should Do Speed Work

Why Runners Should Do Speed Work

(This post originally appeared on Runkeeper’s Blog. As an ambassador for Runkeeper, I share articles on their website and republish them here as well for you to read.)

Like many runners, I have developed a love-hate relationship with speed work. I don’t exactly love the stomach-turning, lungs-burning, legs-fatiguing sensation of mile repeats. During the workout itself, I’m counting down the intervals until I can be done.

However, I love the benefits of speed work – from running faster to increasing my resistance to fatigue, speed work is inarguably essential if you are trying to improve your paces or achieve a goal time in any race. Yes, even the marathon! Even if you don’t like to do it, here are some reason why every runner should do speed work. At the end of the post, I’ll share some of my favorite speed workouts with you!

Why Runners Should Do Speed Work



What is Speed Work? 

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.

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 receive 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.

(If you’re interested in adding speed work to your training, consider hiring a running coach!)

When NOT to Do Speed Work:

Many runners want to 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.

(Just ran a race? Here’s how to recover from a half marathon and marathon!)

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 4-5 mile repeats at 10K pace with 3 minute recovery jogs in between each repeat. 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. Be sure to always include a 1-2 mile warm up and 1-2 mile cool down with your speed work. 

No matter what speed work you do, remember to always run at the appropriate pace (not too fast but also make sure you are working hard enough!), stop if you experience actual pain, and learn to embrace running hard

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Linking up for Coaches’ Corner! 

What speed workouts are your favorites?
What type of workout had the most impact on improving your running?
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20 Responses

  1. I LOVE that you wrote upfront how everyone can benefit from speed work and, I think, especially newbie runners. Why do they think you already need to be fast? My clients used to always come back at me with that and I loved seeing them get faster within a few sessions.
    This is a very well thought out post and you hit all the highlights.
    Mile repeats are my definite “love to hate” because they are painful but really improve speed and endurance.

    1. Thank you! I never understand when people tell me they can’t do it – the speed is always relative and that’s what’s so beneficial about doing speed work. And it’s so empowering for runners of all levels!

  2. I like that fartlek workout you posted because it’s nice and simple and makes a treadmill run go by a little faster. I love speed work because I feel like super woman once it’s done. I get nervous beforehand and then just do one interval at a time. I haven’t done it in a long time!

  3. I love speedwork and honestly, easy days are the hardest for me because I don’t get a ton of satisfaction out of writing “easy 6” or whatever in my training log like I do after a hard speed session (although I know the easy days are still important and I do them). I think most runners can benefit from including speedwork and agree that it does not always have to be on the track! As long as the road is clear and relatively free from traffic, it works well.


    I go through phases where I love speed work and phases where I am soooooo over it. I like to run hard and push myself and feel like a badass afterward, but sometimes it’s a drag to have to think and plan and go back and forth so much during a workout. Sometimes I just crave an easy or long (ish) run where I can zone out and not worry about effort or pace. I guess it’s a good thing they all have a place in the training cycle!

    You have a fartlek on the docket for me today…I think I like those more than conventional speed work. They inject a little fun and energy into the run but the intervals aren’t so rigid and intense.

    1. Oh I totally get what you mean about running back and forth on a long run! I go out of my way to find long uninterrupted paths because otherwise mentally I cannot handle it. And I’m glad to hear you like the fartleks! I’ll keep those in mind 🙂

  5. Great roundup of reasons and workouts to do speed work! I am definitely a fan of shorter intervals versus longer mile repeats… mostly just mentally, I find the longer ones so much harder. Tonight I’ve got a speed ladder at the track on tap.

  6. I love speedwork, particularly those mile repeats! I love to run fast, but at that distance it’s a challenge to stay consistent. You know I love a challenge and that distance is perfect for me. I believe those mile repeats were a game changer for my last 2 Chicago marathons!

  7. How funny, I was literally thinking about how everyone needs to speed work today while I was doing my own speed work! I have a runner working on maintenance right now between training cycles, and I think I’m going to toss a couple speed days her way. It’s good for the brain — keeps runners engaged and interested in what they’re doing even if they aren’t training for anything specific.

  8. My favorite speed intervals are 1/2 mile or shorter. I think hills have had the biggest impact on improving my running – not sure if I like them yet though 😛

  9. It’s interesting how you recommend people running 5 and 10Ks to increase the difficulty of speed workouts as the race grows closer. I think it makes a lot of sense that speed training would be beneficial to distance runners because it would build different muscles and work your core in different ways. My mom used to run marathons back in her day so maybe I’ll ask her what she did because I am planning on running a 10K in a few months and could use some advice.

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