The 10/2: My Favorite Lactate Threshold Interval Workout


Intervals! Just what you've always wanted, right...??
Lactate threshold intervals! Just what you’ve always wanted, right!?

And just like that, the holiday season came and went! Lucky for us, Salty Running is the gift that keeps on giving. Today I’m excited to share a little post-holiday present with you: my all-time favorite interval workout! It’s something that was handed on to me just over a year ago, and I can’t help but want to re-gift it as much as possible.

Interval training can be challenging, but it’s not just for advanced runners. Garlic gave us an excellent intro to intervals post a while back, and Salty pointed out in her post about junk miles that intervals build strength, speed, running economy and leg turn-over. All good things, no matter what distance or pace you prefer.

If you have a desire to improve your endurance (with a little hard work, of course!) in 2015, there’s a good chance that the 10/2 workout could be a valuable addition to your workout arsenal.

Excited? Me too! Let’s unwrap this sucker and learn how to incorporate the 10/2 workout into your training plan!

Step #1: Determine your lactate threshold pace. If you don’t know what lactate threshold is or why it matters, check out my intro to LT. If you need a tutorial on how to run a lactate threshold estimate workout, try this one. The quick ‘n easy (albeit slightly less accurate) method for finding LT pace is go to the McMillan Calculator or the Jack Daniels Calculator and enter a recent race time of any distance. The McMillan calculator will spit out a tiny little number at the top of the screen labeled “vLT.” That is your lactate threshold pace based on the race results you entered. The more recent the race, the more accurate the pace. Over at Jack Daniels, enter your race time and then click the Training tab in your results – the “Threshold” pace will be your pace for these intervals.

Old LT
Circled in red for your viewing pleasure: where to find LT Pace in the McMillian Calculator results

Step #2: Find a relatively quiet route. I wouldn’t recommend going to the track unless you are a glutton for punishment or it’s your only low-traffic option. Same with the treadmill. I hate ‘em, but this CAN be done indoors if that’s your thing. Ideally, you want a loop you can run with as few distractions (intersections, traffic lights, hard turns) as possible. Try to find an area where you won’t get TOO bored and where you can run for 10 minutes at a time without being forced to stop or slow down. I like out-of-the-way residential areas or bike paths with at least a 3-mile loop available.

Step #3: Consider wearing a heart rate monitor. Ideally, interval workouts are best done with one eye on your heart rate and one on your pace. Why heart rate? As you get stronger (and you definitely will with longer intervals like these!) you will start to find yourself capable of running your sets at a faster pace. Without heart rate data, it can be tricky to figure out WHEN, exactly, to start running them faster. It’s also hard to gauge how much to increase the speed.

When I started doing these intervals at the end of 2013, my goal was to keep my heart rate between 168 and 172 beats per minute for each set. That was my lactate threshold training range, which I found by wearing a heart rate monitor, doing the 30-minute lactate threshold estimate workout mentioned above, and looking at my average heart rate for the last 20 minutes of the test. (Quick ‘n easy method: your LT heart rate should be about 70-80% of your max heart rate, if you know what that is.)

In the beginning, I’d hit my goal heart rate range when I’d run at a 7:20 pace. As the weeks went on and I kept running intervals at that pace, I noticed that my heart rate was sinking lower than 168bpm even at the end of the workout. Thanks to heart rate readings, I knew it was time to increase my pace and account for my new-found strength. This, in turn, let me continue improving as my body was ready for it. Now, a year later, I still run in the 168-170 heart rate range for my intervals, but I run them in the 6:20 pace range. That’s right…I’m running 6:20’s at the exact same heart rate that I used to run my 7:20’s! That’s the power of intervals at work, my friends!

Step #4: Do the 10/2

Flickr Commons Image by  San Diego Shooter.
The 10/2 is best done away from traffic. Staying away from leering pervs is always a good idea! Flickr Commons Image by San Diego Shooter. 

Warm up for about 10 minutes, or until everything is loose and your heart is pumping at a steady-but-comfortable rate. Now, get ready for your first 10-minute effort! You will not take a walking break between the warmup and the first set. You WILL take breaks between every set after that.

Here’s where the name, 10/2 comes from. Run at your LT pace/heart rate for 10 minutes, then walk for 2 minutes. That is one set. The number of sets will depend on your current fitness and total weekly mileage. When I first started and was running about 25-30 miles a week, I did 3 sets the first couple weeks. It was a 54 minute workout: 10 minute warmup, 30 total minutes of running at LT pace, 10 minute cooldown, and 4 minutes of total walking in between my sets.

Start with as many sets as you feel comfortable doing, and remember to resist the temptation to run all-out for 10 minutes! Regardless of the number of sets you do, the goal is to run each and every 10 minute effort at nearly the same LT pace, from first to last and start to finish. Overdo it and not only will you find yourself needing to slow down to complete the workout, you’ll tire yourself out more than intended and you’ll have trouble adding additional sets over the course of time. Adding more and more sets at LT pace is the ultimate goal. This is not speed work. It shouldn’t leave you feeling completely maxed out by the end. The magic of LT intervals is that they are long enough to challenge you but not intense enough to kill you.

Try to increase the number of 10-minute efforts you do by 1-2 sets every couple weeks as you feel ready (or as your heart rate prompts!) If you add extra sets and find it difficult to maintain your LT pace for the full 10 minute duration, go back to the number of sets you WERE able to complete successfully and do that for another week or two. If you tend to work rest weeks into your schedule, consider leaving this workout out of the lineup then and pick it back up the following week.

Here’s the cool part: the sky is the limit for total number of sets! For the last 18 weeks of marathon training, I’ve done an interval workout almost every week. Lately, I’ve been pleasantly surprised by how many miles I’m able to tick off in this 10/2 fashion, and at increasingly fast paces. My proudest interval moment happened about a week ago, when I accomplished 11 sets, logged a grand total of 20 miles, and recovered without much trouble at my fastest interval pace yet. I felt like a rock star! Thanks, intervals!


Regardless of your distance goals or running hopes for 2015, the 10/2 workout is a great way to shake up your usual routine. These 10/2 workouts are fantastic for they way they provide  immediate feedback and a very tangible way to watch your progress over time. Highly recommended!

Is this a workout you would do? What’s your favorite workout?

I'm a nomadic runner who loves moving from city to city with my husband and Great Dane. I write about training with a Type-B personality, battling bad running habits, and becoming comfortable with sub-3 marathon racing despite my race-phobia. After a soul-searching year away from running, I'm thrilled and terrified (thrillified?) to be making a major comeback in 2018!

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  1. I did this last night … On the elliptical. Great workout! The first 10 was really hard and the time went slow, but then it got better from there. You did 11 of these?! BEAST!

    1. Yup. You definitely get into a groove with this one, and it’s amazing how your body starts to “remember” and snap right back into the correct pace, even after walking breaks. All it takes is a few strides and BAM! LT pace perfection, set after set. I have to force myself not to constantly check the clock on the first set. It’s the worst! I never run with headphones, but I WILL for this workout because the songs act as my cue. I make myself get through one FULL song and part of a second before I’ll let myself look at the time remaining in the set. That usually gets me beyond the 5-minute mark. If I look down and it hasn’t even been 5 minutes yet, I kick myself for checking too early…which sucks. 11 sets also kinda sucks, but in a good way… 🙂

      Glad you liked it!

  2. I just had a go on the treadmill and those first ten weren’t that bad at all. And the next ones were even better. I defenitely will be doing this workout more often – gotta feeling 2015 is going to be a great year 😉
    (On the elleptical is a great idea as well, will try that too.)

  3. I’ve used this workout as part of my Boston program. Two weeks out from the race I ran a personal best half marathon today – with added bonus of 3rd in my age group. Great confidence booster and I credit this workout with boosting my endurance. I got up to 6 repeats (still can’t believe you did 11!!). Hopefully it helps me on marathon day.

    1. Hi Claire! Congrats on the new half PR and GOOD LUCK at Boston!! I’m so glad you found this workout helpful. It can be a beast, but I’m with you…I find it helpful season after season. And really, I’ve found that 6-8 repeats is kind of the “sweet spot” for me, too. The season I did 11 was pretty extreme, and I don’t think it gave me THAT much more of an edge or boost, overall. (Trial and error/live and learn, right??) Have a blast in Beantown and let us know how it goes!