Splits and Negative Splits in Running

runner looking at watch

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Split is a running and racing term that means the time that it takes to complete a specific distance in running. For example, if you're running 5 miles, your time at each mile marker is called a "mile split." Some runners use splits to see if they're pacing evenly and staying on track to hit a specific goal. So, if you're running a timed mile, you may check your splits every quarter-mile to see if you're on pace.

Tracking your mile splits during a race is crucial if you're trying to reach a specific goal time, like qualifying for the Boston Marathon. (For 2020, the qualifying time for men 18 to 34 years old is 3 hours; for women in that age group it is 3 hours 30 minutes. The times go up by 5 minutes for each 5 year age group.) If you know your split time (or pace), you can estimate your finish time and train to improve it.

How to Track Split Time

Most running watches are equipped to record splits. During a race, you can hit a split button on the watch each time you hit a mile marker. If you have a running watch with GPS, it will track your splits automatically. Calculating your pace (time divided by distance) after a run will give you an average overall pace, not a specific split for each segment. Here is what 1 kilometer split times could look like for a 5K race run in 24 minutes at an even pace:

Split Distance Split Time (minutes) Total Distance Total Time (minutes)
1 km 4:48 1 km 4:48
1 km 4:48 2 km 9:36
1 km 4:48 3 km 14:24
1 km 4:48 4 km 19:12
1 km 4:48 5 km 24:00

Or, for a half-marathon, you can check your split times in 5-kilometer increments. These are split times for a half-marathon with a finish time of 2 hours.

Split Distance Split Time (minutes) Total Distance Total Time
5 km 28:26.35 5 km 28:26.35
5 km 28:26.35 10 km 56:52.7
5 km 28:26.35 15 km 1:25:19.04
5 km 28:26.35 20 km 1:53:45.39
1.1 km 6:14.61 21.1 km (13.1 mi) 2:00.00

How to Use Split Time

During a race, knowing your split time helps you know if you are on track to achieve your finish-time goal. If in the half-marathon example above, you reach the 10K marker at 55 minutes, you are going too fast. Now you know you should slow down a bit to conserve energy. And conversely, if you don't reach that 10K marker until you've been running for 60 minutes, you will need to speed up (this may be your plan if you are aiming for a negative split).

To avoid having to memorize these numbers, some marathon runners use pace bracelets or temporary pace tattoos on their arms so they know what splits they're supposed to be hitting at specific mile markers.

You can also review your splits after races to determine how well you did with pacing and what you can improve for the next race.

Negative Splits

Negative splitting refers to running the second half of a race faster than the first. So, for instance, if you're running a marathon and you run the first 13.1 miles in 2:01:46, and then run the second 13.1 miles in 1:59:30, then you ran a negative split. If your second half is slower, it's called a positive split.

Negative splitting is the ideal way to run a long distance race such as a half or full marathon. However, many runners do the opposite by going out too fast in the beginning, and then slowing down significantly in the second half of the race. It's a common mistake because you feel rested and strong in the beginning, so it's tempting to go out fast.

It takes a lot of discipline and practice to achieve a negative split. Most people can't do it in their first marathon. But, generally, if you can hold back and conserve your energy in the first half of the race so that you can run faster in the second half, you'll perform much better overall.

How to Improve Split Time

Improving your split time generally means improving your overall pace. There are several different ways to train for faster times.

  • Improve your stride turnover: Work on taking more steps per minute.
  • Try interval training: Add bursts of speed to your training runs. Or, do hill repeats.
  • Add a weekly tempo run: Run at a steady effort level, just a bit slower than your usual 10K pace.
  • Try a progression run, in which you gradually increase pace during the course of your run (just like you would do in a negative split): On the perceived effort scale, start out at a 4, gradually increase to 8, and then cool down.

How to Maintain a Consistent Split

Just keeping a steady pace can be challenging for many runners. But working on this can help build the endurance and control necessary to complete a long-distance run or race. You can try strategies such as:

  • Running to music timed to your preferred cadence (say, 160 beats per minute)
  • Timing yourself doing laps on a track, to get to know how a certain pace feels
  • Pace-setting apps or functions on your running watch

What's most important is repetition and practice being aware of what a pace feels like in your body so you can reach it even without a timer.

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