Maximum Aerobic Speed (MAS) and Maximum Heart Rate (HRMAX) are two reference points for determining training intensity.

HRMAX is the maximum intensity of which you’re capable. You’ll typically only reach your HRMAX when specifically testing for it. Maybe you’ll reach it during your most intense interval training sessions, but this is unlikely, since that training isn’t specifically designed to push your heart all the way to its ceiling.

MAS is defined as the minimal pace that will take you all the way to your V02Max, which is the maximum rate that your body can consume oxygen. Your V02Max corresponds closely with your HRMAX, so for our purposes we can think of them as the same intensity level. MAS is a bit tricky to test, because at any pace significantly above your anaerobic threshold, your heart rate will slowly (or quickly) rise toward your maximum. MAS the lowest rate that can get you there.

MAS can be thought of as a way of estimating your anaerobic threshold.

Both MAS and HRMAX are useful; they give you objective tools for determining the intensity of every training session. But you have to measure them with testing to make use of them.

Testing Your HRMAX

First, get an ok from your doctor. The test is very stressful, and could be dangerous if you’ve been sedentary or if you have any cardiac problems.

You’ll need a reliable heart rate monitor that logs data. The standard method is to use a treadmill and to progressively raise the incline, However, a study done in Oslo found a simpler method that reliably raises the heart rate even higher.

This method also uses a treadmill. Warm up, and then run for 3 minutes at the maximum pace you can sustain for this time. Recover with 2–3 minutes gentle running. Then repeat the 3-minute maximal effort again, at the same pace as before. That’s it. Your heart rate should peak sometime before the end of the second 3-minute interval. It’s ok if you can’t complete the full second set, but you should try as hard as you can.

Ideally, your heart rate monitor should sample your heart rate every 5 seconds, or more frequently. The heart tends to reach its peak and then drop back down very quickly. See if this is a setting you can adjust. It’s also important that you be well rested, and thoroughly recovered from previous workouts.

Testing Your MAS

Doing this with laboratory precision is difficult. Getting a rough estimate is simple, especially if you have some running experience and are good at gauging your pace. Just like with the MAXHR test, wait until you’re well recovered, and warm up thoroughly. Then run a 5K as fast as you can. If there’s any way to push yourself even harder during the last kilometer, do so. Your average speed over that last 1K should pretty closely correspond to your MAS.

How to Use These Metrics

Generally, when you’re measuring intensity with heart rate, you’ll refer to your HRMAX; when you’re measuring it with pace, you’ll refer to your MAS.

Let’s look at them in relation to the traditional intensity zones:

Very Light

50 to 60% HRMax

55%–66% MAS

This is the easiest training zone, suitable for warming up, cooling down, or recovery days. While in this zone, you should be able to carry on a normal conversation, or even sing along with the music on your headphones.


60 to 70% HRMax

66%–77% MAS

This training zone is ideal for extended endurance workouts. You should be able to speak in full sentences, but probably won’t be able to sing well. This intensity level works your aerobic system, but doesn’t demand extensive recovery the next day.


70 to 80% HRMax

77%–88% MAS

Many athletes naturally gravitate toward this intensity zone. Which is not ideal-you’ll get benefits from this exercise, but you’ll do better to spend more time either at higher or lower intensities. Coaches sometimes refer to this zone as “the mediocre middle.”

In the Moderate zone you’ll be able to talk, but probably only in shorter sentences.


80 to 90% HRMax

~100% MAS

Somewhere in this zone, you’ll hit your MAS, or anaerobic threshold, which is the intensity beyond which your muscles start to burn and you’ll have to slow down or stop within the next several seconds or minutes. Your anaerobic threshold will vary depending on your genetics, how well-trained you are, and to what degree you’ve done high-intensity training at or above the threshold. This is the intensity range for tempo training and short to moderate races (5K and 10K). In the Hard zone, you’ll have trouble saying more than a few short phrases before having to catch your breath.


> 90% HRMax

100–112% MAS

This zone is the province of high-intensity interval training. Training here offers the maximum benefit to your oxygen uptake, your anaerobic threshold, and your ability to quickly recover from short efforts. It’s also very demanding, both physically and mentally. Generally, you’ll only want to do one workout in this range per week. At the very most two. And you’ll need a recovery day afterwards, with much lower intensity activity. You’ll only be able to sustain efforts in this zone for ten seconds to two or three minutes, depending on how close to 100% you’re pushing yourself. You won’t be able to talk, but gasping, whimpering, and moaning are popular. We will post soon about how to structure high-intensity interval workouts.

How to Use This Knowledge

Once you know your maximum heart rate and / or your MAS, you’ll always know your training zones. You’ll have a much easier time designing a training program, or following a program designed by someone else. While the zones are necessarily imprecise, they make it easy and repeatable to get into the correct general range for any given type of training. And they help you stay out of the wrong ranges, so you’ll be less likely to overtrain.

We hope you enjoy putting this knowledge to good use!