If most of your runs feel “kind of hard,” your aerobic system may never get the signal to improve. That’s the trap of missing your aerobic threshold, the point where your body starts leaning more on faster, less sustainable energy. Push above it too often and you can rack up fatigue without getting faster.
Runners also call this line LT1 (the first lactate threshold) or the first ventilatory threshold. I reviewed lab-testing methods and endurance training research, then translated them into checks you can do on regular roads and trails.
You’ll learn what the aerobic threshold is, how to estimate it with simple cues (talk test, heart rate trends, steady pacing), and how to train around it without turning every run into a grind. You’ll also know what progress looks like so you can validate you’re on the right track. Let’s start with the definition.
What is the aerobic threshold?
The aerobic threshold is the point during an exercise where your body starts to burn fat to fuel physical activity, while the primary energy source remains carbohydrates. Your muscles produce more lactic acid than your body can remove—about 2 mmol/l. The intensity below it is a recovery run; the load above AT is aerobic running. You can easily work out at your aerobic threshold intensity for several hours.
Why should I work on my aerobic threshold?
Improve physical fitness
When working at or post the aerobic threshold, the body learns to use oxygen more efficiently to synthesize energy. The heart and lungs work more effectively, and the body becomes better at utilizing oxygen to generate power. Ultimately, your cardiovascular fitness improves.
Achieve a better running economy
The more effectively you run, the less energy you burn to keep pace. Increasing the running economy leads to significant progress with running speed.
Track your running progress
Runners with a higher AT can maintain a fast pace longer before reaching the point of fatigue. The better your running shape is—the higher your aerobic threshold level.
Healthy weight loss
Runners with excessive weight experience an increased load on their heart, cardiovascular system, muscles, and joints. You need to exercise at and slightly above your AT for a safe and sustainable weight decrease.
Reduce the risk of injuries
Regular working at or above the aerobic threshold help your body adapt to the increased intensity. So, your muscles are less likely to become fatigued under extreme or durable workouts.
How to find my aerobic threshold?
There are three ways to find your AT.
Lactate threshold test
It is the most precise method of measuring your aerobic threshold. It involves taking a small blood sample from your earlobe or finger before and after exercise. The AT is the point at which there is an exponential increase in blood lactate levels.
RER test
Another option to accurately identify your aerobic threshold is measuring the respiratory exchange ratio (RER). You’ll have to run on a treadmill in a lab with different intensities and breathe through a valve. The balance of carbon dioxide produced and oxygen inhaled defines your AT.
Measuring your heart rate
A heart rate monitor is the most common way to find your aerobic threshold. The AT is typically associated with a heart rate of approximately 75-85% of your maximum heart rate. To roughly calculate your max heart rate, subtract your age from 220.
DIY aerobic threshold check you can do outdoors
No lab required. You can get a practical aerobic threshold estimate with a normal run. Think of it as the fastest effort that still feels steady and repeatable. Breathing stays calm, and you could keep going for a long time.
Use two body cues first. With the talk test, you can speak in full sentences without gasping. With the nose-breathing check, you can keep your mouth closed without strain. If either cue breaks, you’re likely above aerobic threshold.
Then run a simple step test. Pick a flat loop or a gentle, steady hill. Warm up for 10–15 minutes at an easy jog. Increase effort slightly every three minutes while you watch your breathing, not your pace. When the cues start to fail, back off just enough to regain control. Hold that effort for 10–15 minutes. Record your average heart rate and the pace you held during that steady segment.
To sanity-check the result, repeat the test on another day with similar conditions. Heat, dehydration, poor sleep, and stress can raise heart rate at the same pace. Stop if you feel chest pain, dizziness, or unusual shortness of breath. If your heart rate keeps drifting up during the steady segment, slow down and retest.
Use the number as a training ceiling. Keep most easy runs under it, and let hills push pace down while heart rate stays steady. Retest after six to 10 weeks and update your zones.
What is a good aerobic threshold?
A healthy AT is around the heart rate of 130-135 bpm. The pace and time you can run at your aerobic threshold depend on your age, physical fitness, and endurance. The more your running experience is—the faster your AT and the longer you can keep it without fatigue and injury.
How to improve aerobic threshold?
There are several ways to improve your AT.
#1 Increase your weekly mileage
Making more miles per week is the first step to lowering your heart rate while running at any intensity. Over time it will upgrade your heart, lungs, and legs to prepare your whole body for the next steps. Increase your mileage gradually—it will prevent injury and give your body time to adapt to the amplified activity.
#2 Incorporate running above the aerobic threshold intensity
Fartlek and interval workouts provide the necessary stress for your body to progress. These types of exercise alternate periods of high and low intensity. It is an effective way to improve your AT because your body becomes better at using fat as fuel.
#3 Do long runs once a week
You should perform long runs once a week at around aerobic threshold intensity for a prolonged time. It improves your AT and overall endurance by increasing your body's ability to perform at moderate intensity before fatigue appears. You’ll improve your aerobic threshold the most when extending the long runs up to 2-2.5 hours.
Four tips to improve your aerobic threshold
Improving your AT can take time and effort, but it’s worth it. These tips can help you make the most of your workouts and see the results you are striving for.
Adequate fueling before running
Eating a balanced diet that includes carbohydrates, protein, and fat will help ensure your body has the nutrients it needs to perform at its best. In addition, drinking plenty of fluids before, during, and after exercise will help keep your body hydrated and will help prevent fatigue. Lastly, avoid eating right before training and running when you are hungry.
Enough amount of sleep
Getting enough sleep is vital for overall health and well-being and impacts your aerobic threshold. Sleep helps your body recover from the stresses of exercise and top up the energy stores. Not enough sleep and intense training lead to burnout and injuries in weeks.
Decrease overall stress
Stress harms your current AT, and chronic stress leads to sustainable changes in your body that degrade your aerobic threshold. On the other hand, running is a way to escape from stress in your life. Although, if you're not feeling well mentally, consider running with lower intensity.
Quit smoking
Smoking pollutes your lungs and makes it harder for your body to get the oxygen it needs during exercise. That’s why progress with running is almost impossible while smoking. Quitting it improves your AT in just several weeks.
The difference between aerobic and anaerobic thresholds
The aerobic threshold is the point at which your body starts to need more oxygen to produce energy. In contrast, at the anaerobic threshold, your body can no longer keep up with the oxygen demands of muscles and starts to generate power without oxygen.
You work on 50-60% of your maximum heart rate at AT, which is a substantial effort. You reach the anaerobic threshold at 80-90% of your maximum heart rate, and it feels like backbreaking work.
The aerobic threshold is essential for people trying to lose weight and improve overall cardiovascular fitness. The anaerobic threshold is crucial for people trying to boost speed and endurance.
Final thoughts
While being a crucial runner’s benchmark, the aerobic threshold isn’t constant throughout your lifetime. It can change together with your running progress and depending on the environment you’re training in. A good rule of thumb is to check your heart rate zone and threshold points every 6 months. It will help you stay safe, get your body the necessary stress, and improve your running performance sustainably.
FAQs on aerobic threshold
What does “aerobic threshold” mean for runners?
Aerobic threshold is the fastest steady effort you can hold while still feeling controlled. You are working hard enough that breathing is deeper, but you can keep going without fading fast. It often sits between easy running and tempo running.
Is aerobic threshold the same thing as lactate threshold or anaerobic threshold?
No, aerobic threshold comes first, and lactate (anaerobic) threshold comes later. Aerobic threshold is the top end of steady aerobic work. Lactate (anaerobic) threshold is a higher effort where fatigue builds faster and you can hold the pace for less time.
How can I estimate my aerobic threshold without a lab test?
You can estimate it with a steady run and the talk test. After an easy warm-up, increase effort until you can speak in short sentences but not chat freely. Your heart rate at that effort can be a useful anchor, but treat it as a range, not a single number.
What should an aerobic threshold run feel like?
It should feel “comfortably hard,” like you are focused but not straining. Breathing is noticeable, and you can say a sentence or two at a time. If you are gasping or cannot talk at all, you are probably above it.
Why does my aerobic threshold pace feel slow some days?
Heat, hills, wind, stress, poor sleep, and dehydration can all push heart rate up at the same pace. That can make an aerobic effort look slower on your watch. On those days, match effort instead of forcing pace.
How often should I train near aerobic threshold?
Most runners do well with one aerobic-threshold focused workout each week, plus one longer run and several easy days. A simple option is a 10 to 15 minute warm-up, then 20 to 40 minutes steady at aerobic threshold effort. Keep the next day easy so you absorb the work.
How long does it take to improve aerobic threshold?
You can often feel progress in four to eight weeks if you train consistently. Bigger changes take a few months of steady mileage, long runs, and controlled moderate work. Retest every couple of months since fitness and conditions change.
When should I stop a threshold workout and get medical help?
Stop and get urgent help if you have chest pain, fainting, severe dizziness, or sudden shortness of breath that is out of proportion. Also stop if you feel an irregular heartbeat that does not settle with walking. If something feels off in a new way, play it safe and get checked.
I completed my first 10K on a dare. In a year, I ran a half-marathon. Another year later, I finished a marathon race. Today I run 4 marathons a year and a half-marathon every week. I learned everything about running the hard way. So, I help runners achieve better results easier.
