Are you a slow runner? Well, maybe you should be more often. If you're training for a race of longer duration like a Spartan Trail race and want to get faster, but you're currently running all of your training runs at a "hard" pace, you may be sabotaging your recovery and — consequently — your speed in the long run.

But every runner is different, so what exactly are your "hard" and "easy" paces, and how much of your weekly mileage should be devoted to each type of training if you really want to improve your speed?

This can all be easily explained using the 80/20 training rule of running. Here's a quick rundown of what you need to know about the rule itself, and the types of workouts you'll perform during polarized training. 

What Is the 80/20 Rule in Running?

Aside from some of the golden rules of running — like not increasing your total weekly mileage by more than 10% week over week, and keeping your long run to a third or less of that total — there are several other widely agreed upon ideas that can help you perform your best while training for a race. The 80/20 training rule was made popular by University of Agder sports science professor Dr. Stephen Seiler, and the "polarized" training technique has since become accepted and normalized across the global endurance community. But what is it?

Related: Every Spartan Trail Race on the U.S. Schedule: Dates, Details, and More

The principle of this rule is relatively straightforward: Eighty percent of a runner's training should be done at low intensity, and 20% should be done at a high intensity that feels hard, such as a tempo run or interval training. This type of training regimen can help runners increase their speed and performance while training for a race.

For example, a study published in the Journal of Strength and Conditioning Research found that runners who followed an 80/20 training program improved their 5K time by an average of 2 minutes, compared to those who trained at the same intensity throughout their training program. So, how can you accomplish something similar?

What Should Your "Easy" Runs Look Like?

If you want to improve your base endurance, work on your breath work, and actively recover from harder efforts, easy runs are your way to go. Depending on the length of the race for which you're training and — subsequently — your required weekly training mileage, the number and length of your easy runs will vary, but here are a few guidelines to keep in mind:

• Keep it in Zone 2, or a "steady" pace
• Your rate of perceived exertion (RPE) should be a 2-4 on a scale out of 10
• You should be able to hold a conversation the entire time
• A good pace is likely 2 minutes (or MORE) slower than your 5K pace
  
  

So, if you typically run a 5K at a 25-minute pace (just over an 8-minute mile), then you should be running your "easy" runs at a 10-minute per mile pace (at the fastest). 

If you have trouble slowing down during training runs, try running without headphones — no music, no podcasts, nothing. 

And remember, these easy runs should make up 80% of your entire training load. If you're training five to six days a week, at least four of them should be easy. For example, if you're on a 30-mile-per-week plan with six days of training, you might do a 10-mile, easy long run on Sunday, two, 3-mile tempo runs spread across Tuesday and Thursday, and space the remaining mileage across Monday, Wednesday, and Friday. (This might look like 4 miles on Monday, 5 miles on Wednesday, 5 miles on Friday.)

Related: The 7-Day Run Long, Stay Strong Training Program With Trevor Franklin

What Should Your "Hard" Training Days Look Like?

Tempo Runs

Tempo runs are an amazing way to increase your aerobic endurance and teach your body to effectively convert lactate into energy once again so you can run faster and farther. Because these Zone 3, comfortably hard runs are performed just below your anaerobic threshold (AT) — the point at which there isn't enough available oxygen to use as fuel and your body relies on glycogen stores to keep going (typically around 75-80% of your maximum heart rate) — they are supposed to feel difficult, but you should still be able to maintain your speed for 20 minutes or more (and ideally up to 60 minutes).

If you have a go-to 5K race pace, a good tempo run pace might be about 30 seconds slower per mile than that pace. If you are running so fast that you cannot speak at all, you're above the threshold and need to slow down. If you can speak more than a few broken words, it's time to pick up the pace. 

Again, if you're following the 80/20 rule and training five to six days a week, that leaves room for four days of "easy" training, and one day to tackle a tempo run (unless you are running higher weekly mileage such as 30+ miles, and your tempo runs are only 3 to 4 miles each, in which case you can do "high-intensity" on two training days). You can also swap out a tempo run for other high-intensity workouts, like interval or fartlek training.

Related: The 7 Spartan Rules That Will Make You Run Like Hell

Interval Training

Studies have shown that incorporating high-intensity workouts into a training program can help to increase running speed, endurance, and economy. When you think of high-intensity interval training, you might picture short repeats of heart-rate shockers like burpees and jump squats, but you can also get a really effective and "hard" running workout in using intervals. 

Using the 30+ weekly mileage example, a great interval running workout might look like 6 x 800-meter repeats at 5K pace with a 90-second rest between each, or 2 x 1.5 miles at 10K pace with a 3-minute rest in the middle. As always, remember to perform an easy warm-up and cool-down before and after hard workouts to prevent injury, and don't do these workouts back to back. (In other words, if you're doing interval training on Tuesday, wait until at least Thursday to do another "hard" workout.)

Fartlek Runs

If you're feeling burnt out or just starting a new training plan, then fartlek runs (which is Swedish for "speed play") are a great way to incorporate variety into what is likely a fairly rigid training schedule otherwise. Unlike intervals, you won't be fully "resting" during the rest period, rather you'll be jogging at a much easier pace. (And you shouldn't feel like you have to rest either, so if you're totally winded, you may need to slow down.)

Related: Do This Simple Postural Test to Quickly Correct Your Running Form

Other than that, there's no real structure to fartlek runs. You can focus your workout on sets of 30- to 60-second hard, intense efforts (to the top of the hill or to the neighbor's mailbox) followed by a few minutes of jogging. Get your heart rate up, have fun with it, and — above all — ensure that your "hard" mileage doesn't exceed 20% of your weekly total. 

Want to commit to something hard this year? From trail running to obstacle course racing, functional fitness, mountain biking, paddle boarding, and more, here's everything you need to conquer your next endurance adventure!