The best running plans include a mix of sessions designed to target different physiological systems. In this article, we’re focusing specifically on what lactate threshold is, and how interval sessions and tempo runs are used to improve it. Sometimes the terms, intervals, threshold and tempo can get confused, so we are breaking them down for you.
What is the Difference Between Interval Training and Threshold Training?
Interval training is a training structure. It simply means breaking a workout into short hard efforts (reps) with a full walking recovery in between.
Threshold training is a training principle. It refers to running at an intensity that improves your lactate threshold – the point where lactate begins to accumulate faster than your body can clear it.
The overlap between these two terms: Threshold workouts are often done in an interval format – you will run your intervals at your threshold pace with a short recovery between efforts. That means the session is both interval training (the structure of hard efforts and rest) and threshold training (the goal of improving your lactate threshold) at the same time.
However, not all interval sessions are run at your threshold pace. Some intervals are performed at a faster intensity to target different physiological systems and deliver different training benefits. For example:
Threshold intervals → Run at or close to your lactate threshold pace. A hard effort, but not pushing completely flat out. Sustainable for longer reps. Common in all training plans.
VO₂ max intervals → Run faster than threshold pace, at an intensity that maximises oxygen uptake. Very hard effort, typically shorter reps, with heavy breathing. More common if training for shorter distances like a 5K.
Speed/anaerobic intervals → Run well above threshold pace. Very short, fast efforts focused on neuromuscular power and anaerobic capacity, with full, longer, recovery between reps. Common for runners looking to maximise speed for much shorter races.
In your plan, you'll most commonly be doing your intervals at threshold pace because distance performance improvements come from raising your lactate threshold. If your goal is to sharpen your speed over a shorter distance like the 5K, VO₂ max intervals will also benefit you.
Aerobic vs Anaerobic
When you run at easy paces, your body is working aerobically – using oxygen to break down carbohydrates and fats for energy. This is efficient and sustainable for long periods.
As you run faster, your body starts to rely more on anaerobic energy – a quicker but less efficient process that produces lactate as a by-product. Your lactate threshold is essentially the point where your body will tip from primarily aerobic to increasingly anaerobic work.
You'll sometimes see Runna's coaches refer to your aerobic base – this simply means the foundation of aerobic fitness you build through easy and steady running. The stronger your aerobic base, the more efficiently your body uses oxygen at higher intensities, which is what also allows your lactate threshold to improve over time.
The Science Behind Thresholds
Threshold refers to the intensity at which lactate begins to build up in your blood faster than your body can clear it. When you run, your body breaks down carbohydrates for energy, producing lactate as a natural by-product. At easier paces, your body can clear and reuse this lactate efficiently. But as the pace increases, lactate starts to accumulate.
That build-up is what creates the familiar burning sensation in your muscles that makes your legs feel heavy. If you go much harder than your threshold, fatigue builds quickly and you’re forced to slow down or stop. Your lactate threshold, therefore, is the highest intensity you can sustain for a prolonged period without that rapid build-up overwhelming you.
If you're well trained, your body is able to create and clear out the lactate at the same rate whilst you're running. During these runs, you will not reach your lactate threshold. However, if you up the pace and start to run faster, you will get closer to this threshold and eventually above it.
How to Calculate Your Lactate Threshold and Threshold Pace
The most accurate way to calculate your threshold is by doing a laboratory test, however this is not a convenient or practical option for most people. Other options include:
Heart rate: Your running threshold is around 80-90% of your maximum heart rate, also known as Zone 4 (threshold zone). By using heart rate, you can track how your threshold pace changes as you get fitter. You can learn more about heart rate in the article below.
Threshold Time Trial (30-60 minutes): Your threshold pace is the fastest pace you can sustain without fatiguing – roughly what you could hold for about an hour.
If you’re an experienced runner and have run half marathons and marathons, try a 60-minute time trial for the most accurate result.
If you’re newer to running, or want a simpler option, do a 30-minute test instead – run at a pace that feels challenging but sustainable for the duration and take your average pace from the final 20 minutes as your threshold pace.
Both methods will give you a strong benchmark to guide your training, the key is finding a challenging pace that you can hold without completely fading.
If possible, use a local race that lasts roughly the same amount of time as your threshold test, or you could use your results from a recent race.
Go on feel: Threshold effort is one that feels hard, but that you can sustain for up to an hour. It won't leave you gasping for breath like a flat- out 5k race or a sprint would.
What are Threshold Intervals and How Should They Feel?
Ultimately, if you can improve your lactate threshold you will be able to run faster for longer. You do this by running threshold interval sessions – they train your body to become more efficient at clearing lactate.
Intervals vs Tempo Runs: What's the difference?
In your Runna plan there are two separate types of sessions, Intervals and Tempo. Both sessions sit close to your threshold pace, which is why they’re often confused, but they stress your body in slightly different ways. For a full breakdown of how each session works, see our guide below.
Get a Tailored Training Plan to Become a Better Runner
With Runna, you can follow a personalized training plan tailored to your goals, fitness level, and schedule. Each week includes a mix of interval sessions, tempo runs, long runs, and easy runs, all designed to make you a stronger, faster runner.