Establishing the correct 5k cross country race pace based on your current fitness is the single most important aspect to finishing with your best possible time. Let’s dive in to what makes this so important and how you can set a new PR by following one simple guideline.

Any runner who has been training and racing competitively has heard about needing to use proper pacing. But what exactly does that mean? Some coaches advocate for a hard start to get position or “bank” some time, some like to see surges in the race to try to break an opponent, and others like to utilize a sit and kick. While all of these strategies have merit, the science is clear on how to hit your best time. Even splits with a slight acceleration at the finish is the scientific answer to your pacing dilemma. Let’s take a look at the kilometer splits of the recent 5k world record set by Joshua Cheptegei:

1k – 2:32.3

2k – 2:31.8

3k – 2:31.1

4k – 2:30.3

5k – 2:29.9

The largest difference in splits was between the first and last kilometers, a difference of only 2.4 seconds, or only .24 seconds per 100 meters! A cruise control on a car could barely do any better. So why are even (and slightly negative) splits so effective? The answer, again, is in the science.

Your body utilizes three energy systems to do the work in your 5k race: the aerobic system, anaerobic glycolitic system, and anaerobic lactic system. First, let’s toss out the anaerobic glycolotic system. It only accounts for probably .0001% of the race. By the time you are 10 seconds into the race it’s totally used up. The aerobic system and the anaerobic lactic system will now compete to provide you energy for the race. The anaerobic lactic system provides much more power for the task, but it begins to fill the muscles and bloodstream with lactate. The aerobic system then needs to do double duty, both fueling the body AND removing the built up lactate so that the muscle contractions don’t begin to shut down. Too fast of a pace early on in the race will create a flood of lactate into the muscles causing you to get tired much faster. A well-paced effort will keep these two systems in balance throughout the race and keep a little extra anaerobic power in the tank for a final fast push for the finish.

So…..My one big point for you today? Go too fast too early and bad things happen. It’s science.

So, use your recent racing and training efforts to help you determine your appropriate pace for your next race and get out there and set that shiny new personal record.


Don’t know what race pace is right for you?  That’s what I’m here for!  Fill out the following form to get a free consult to get you on your way to your best times ASAP!



Ben Tilus – Owner/Head Performance Coach – XLR8 Performance Lab