If you watch a motor race, you might notice that the cars get faster toward the end. Because they start out with a heavy fuel load and burn it over time, they get lighter, enabling them to gain more speed on each lap. Although a human body and a racecar are nothing alike, you also have the ability to speed up over the course of a race, whether it be a 10K race or a half marathon—it’s called running a negative split. It takes work to do so, but it’s worth the effort if your aim is to finish stronger and faster than you thought possible. Below, find everything to know about running negative splits, including how to pull it off.

What Are Splits?

In running, a split is the time it takes you to run a portion of a given distance. For example, if you’re running a 5K, you might look at your times for miles one, two, and three, with each of those being a split. Your goal might be to run with consistent splits (i.e., a steady pace), positive splits (getting slower as the run progresses), or even negative splits (getting faster as the run progresses).

What Is a Negative Split In Running?

Achieving a negative split simply means that you ran the second half of your run or race faster than the first half. For example, in a 10K, that would mean your second 5K was faster than your first. A negative split is one type of progression run, which is any run where you intentionally start at a slower pace and increase your speed as the run progresses. 

While that might sound difficult—and it can be—it’s not as impossible as it may sound.

“We typically use the first few miles to get the body and the breath properly warmed up and adjusted to the distance of the run,” says Peloton instructor Mariana Fernández. As a result of your slower starting pace, you’ll set yourself up to have the energy in the latter half of your race to increase your speed. 

In addition to helping you hit your goal time, chasing negative splits can also help you pace effectively and efficiently. “I have found that we can easily let nerves, adrenaline, and excitement shoot us like cannons out of the start line,” Mariana says. “It can be demoralizing and downright painful to use all of your fuel [at the beginning] and suffer the second half of the race. If you learn how to measure and conserve early on, it gives you the freedom and fuel to shift gears and finish stronger than how you started.”

The Benefits of Running Negative Splits

Running negative splits—whether during a race or in training—is completely optionl, but it can come with some pretty promising benefits, both for your mental and physical running game. 

It Eases Your Body Into Intensity

One way to think of running a negative split is that it’s a sort of elongated warmup. On almost every run, ride, or row, you’ve probably noticed that your body needs time to get going. Even on days you don’t feel motivated, you might suddenly find that, five or 10 minutes in, you start cruising.

It typically takes the first few miles of a run to get your body and breath warmed up and adjusted to the effort, Mariana says. “Negative splits allow you to gradually land in your pace and then access strength and speed as you continue to run longer.” You start slower and easier, and as your body acclimates to the challenge and loosens up, you’re able to kick things into a higher gear.

Warming up well primes your respiratory and circulatory systems to work, slowly raising your heart rate (which reduces the stress put on your heart), increasing blood flow (which carries oxygen and nutrients to your muscles), and elevating the temperature of your muscles (which improves flexibility and efficiency), according to the American Heart Association (AHA).

It Stokes Your Motivation

Heading out on a run with the goal of running negative splits can give you something to aim for, which can be particularly helpful when you’re feeling uninspired by a run-of-the-mill workout session. Think of it as a mini goal. A lot of the time, we’re just trying to get through a workout—but when you have a short-term goal right in front of you, such as running the second 30 minutes faster than the first 30, you might find that it’s easier to stay motivated and push yourself rather than simply cruising through (yet another) easy run.

Multiple, mini positive-feedback loops strung together can combine to form a big positive-feedback loop that proves to you, over and over again, that you’re capable of achieving something bigger. Pretty much every running blogger who’s touched this topic writes of their stronger confidence, reduced anxiety, and increased enjoyment as a direct result of working toward negative splits.  

It Improves Your Pacing and Performance

Do you ever head out on a long run only to use up all your energy at the beginning and struggle through the last few miles? Using negative splits helps you learn to pace yourself, so you have more control of a run or race and can avoid burning out. “It makes sure that you have something left in the tank in the latter half of the race,” Mariana says. “Using negative splits really keeps you measured and provides a specific strategy for how to approach your run.”

Starting slow helps you conserve your stores of glycogen, the sugar your body uses for energy. If you start your run too fast, you risk depleting your glycogen stores, which can lead to “bonking,” or feeling like you don’t have the energy to keep up the pace or even continue your run.

Learning to push your pace on tired legs can also build mental toughness and help you learn to listen to your body and find your physical and mental limits. “It's a check in with your body and the ability to stay steady enough throughout so you can shift into speed and power at the end and have a strong finish,” Mariana says.

How to Practice Running Negative Splits

If you’ve decided to aim for running a negative split at your next race, want to learn to better control your pace, or simply want to switch up your training, there are a few strategies you can employ to work toward negative splits or give this type of training a try. In general, you can implement negative split elements in other types of training, Mariana says. Specifically, negative split training can fit well into your speed workout days or long runs.

That doesn’t mean, however, that you should include negative splits in every run. A good example? Your recovery run or easy-run days—they’re important for keeping your body loose and helping it heal. Pushing yourself every day, every run, will provide diminishing returns and increase your risk of injury. “Some races and training runs are you just getting to know your body and your paces,” Mariana says.

You might also want to work your way up to negative splits. If you’re just getting started with running generally, or you’re coming back after a layoff due to injury or a deserved break from pounding the pavement, don’t jump back into negative-split runs right away. Make sure you can finish, say, a 5k run comfortably and focus on your ability to maintain a consistent paice before you start trying to run the back half of the workout faster.

When you are ready, here are a few ways to train for achieving negative splits:

Try Escalating Intervals

One way to train for running negative splits is to try to push your pace during your speed workouts. For example, during an interval running workout, Mariana says you can try running one of your fast intervals, note the time, and then on the next fast interval, aim to beat that time. The same ritual can be replicated during a hill repeat workout. “You can practice not going all out on the first hill and finding that sense of control and conservation,” she says, “then see if you can go faster or attack the last hill of your run.”

Break Your Run Into Thirds

This type of progression run is like a half step toward achieving a negative split. Instead of breaking your run into first and second halves, break it into thirds. So, let’s say you’re running six miles. Run the first two at an easy pace, the second two moderate, and go for a strong but controlled finish on the last two. After a few of these runs, you’ll be ready to try a negative split.

Do Fast-Finish Long Runs

Perhaps you’re signed up for a half or full marathon, and you’ve begun your long runs of 10 or 12 miles. Take the first 75 percent of the run at an easy pace, then go for your race pace in the last couple of miles. Try this a few times, and extend the length of the race-pace portion a little bit each time. You’re gradually increasing your ability to hold a faster pace for the back half of your run.

Try Alternating-Pace Runs

These runs—during which you alternate easy pace and race pace—build endurance but also help you develop pace control. For example, if you’re doing an eight-mile run, you’ll alternate one mile easy, one mile at race pace until you’re finished. Ideally, your race-pace miles will clock in at about the same pace, but you should aim for your final mile to be your fastest. The idea is that if you can control your pace from mile to mile, you can control your pace over longer periods too.   

How to Use Negative Splits In a Race

There are three keys to pulling off a negative split in a race: pace, pace, and pace. 

While a negative split is, by definition, running the second half of the race faster than the first half, you need to think of breaking your race into three parts: a restrained pace early on, patience in the middle, and a smart yet sustainable push toward the end. “Negative splits are really about knowing how to pull back and take your time to find different pace targets,” Mariana says. Rather than thinking of it as half easy, half hard, think of it as a slow build.

For example, if you’re running a half marathon, you’d want the first few miles to be restrained—maybe 10 or 15 seconds per mile slower than your goal pace. Then, once you’re warmed up and settled in, increase to your race pace and hold it for the next five to six miles. On the last couple miles, hit the gas—aim for anywhere from five to 15 seconds per mile faster than your target pace. (The same general logic applies to a full marathon, breaking the race into thirds.) When you look at your overall time and break the race in half instead of into thirds, you’ll find that you achieved a negative split. 

All of this depends, of course, upon knowing what your goal pace actually is. Don’t guess—that’s the key ingredient in the recipe for disaster. To find your race pace, you’ll need to work off previous race results and your training runs. From those runs you should also know the general range of where your heart rate should be when you’re running at race pace, so those early miles should feel easy.

Mostly, it’s important to run with your head, not your heart. Don’t overcorrect or let adrenaline take over, and get pulled along by runners who are clearly faster. “Even as an experienced runner, it's easy to get confident and feel like you can start strong and feel like you can sustain it the whole way through,” Mariana says. If you run according to your data, know your targets and stick to them, you’ll achieve a negative split successfully. 

How to Decide If Negative Splits Are for You

Although running with negative splits might be a popular goal (and come with some tempting benefits), running the back half of a race faster isn’t necessarily for everyone. If you have a history of struggling late in races, you want to build your race-day confidence, or you just want to build more long-term endurance, working toward achieving a negative split will help you get there.

A negative-split race might not be worth pursuing, however, during shorter races or courses with varying terrain or elevation. Moreover, if you’re not feeling great (whether from sleep deprivation, illness, or injury) or are experiencing symptoms of overtraining, for example, negative splits might not be the move. “It really comes down to syncing with your body during the run to see when you do have the drive to access speed and strength in the second half of your run, or if you have to back off to keep your body safe and stay in it,” Mariana says. 

Most critical of all, running should be fun. If you find that pursuing a negative split takes the joy out of your training for a specific race—or running in general—rethink why you lace up your running shoes. Pursuing a negative split should be a positive thing. If it isn’t, find another running goal to aim for—there are plenty.