Stop guessing, start improving. Understanding your running thresholds is the key to unlocking faster times, greater endurance, and more efficient training. This guide breaks down the essential thresholds, how to identify them, and, most importantly, how to improve them with actionable strategies. Let’s dive in!

Aerobic Threshold (AeT): Your Fat-Burning Engine

What it is: Think of your Aerobic Threshold (AeT) as the highest gear in your fat-burning engine. It’s the point where your body is primarily using fat for fuel, before it starts relying more heavily on carbohydrates. This happens around 65% of your maximum oxygen uptake (VO2 max).

How to feel it: At the AeT, you’re at a moderate, sustainable pace. You’ll notice a slight increase in your breathing, but you can still carry on a conversation comfortably. If you can’t speak comfortably, you’re above your AeT.

How to boost it: A higher AeT means you can run longer, more efficiently. To improve it, focus on low-intensity endurance training, like long runs at a conversational pace. This teaches your body to burn fat more effectively and delay the switch to carbohydrates. Think Zone 2 training: long, steady efforts that build your aerobic base.

Anaerobic Threshold (AT) / Lactate Threshold (LT): Where the Burn Begins

What it is: Your Anaerobic Threshold (AT), also known as your Lactate Threshold (LT), is the point where your body starts producing more lactate than it can clear. This happens when you’re working hard enough that you can’t get enough oxygen to keep up with your energy demands. This is a key performance indicator, and it’s closely related to two other thresholds:

• Maximal Lactate Steady State (MLSS): The highest intensity you can sustain where lactate production equals lactate clearance.
• Onset of Blood Lactate Accumulation (OBLA): The point at which lactate significantly increases in the blood (typically around 4 mmol/L).

How to feel it: You’ll notice a burning sensation in your muscles, increased fatigue, and difficulty maintaining your pace. Your breathing will be labored, and you’ll struggle to hold a conversation.

How to boost it: To improve your AT/LT, you need to:

• Improve your VO2 Max: Increase the amount of oxygen your body can use.
• Enhance lactate clearance: Help your body remove lactate more efficiently.

High-Intensity Interval Training (HIIT) is a game-changer here. Short, intense bursts followed by recovery periods push your body to adapt, boosting both your VO2 max and lactate clearance. The Norwegian model of lactate threshold training is another great option, which uses high-volume, lower-intensity efforts to build these thresholds. Remember: proper recovery and nutrition are critical when using HIIT.

Ventilatory Thresholds (VT1 and VT2): Listening to Your Breath

What they are: Ventilatory thresholds are about how your breathing responds to exercise intensity.

• VT1: Breathing becomes noticeably deeper and more frequent as lactate begins to accumulate, but it’s still below your lactate threshold.
• VT2: Coincides closely with your lactate threshold. Breathing becomes very heavy, and talking becomes difficult as your body tries to expel excess CO2.

The Respiratory Compensation Point (RCP) is closely related: it’s the point where ventilation increases rapidly to vent CO2 due to excess lactate. At RCP, you’ll experience very heavy breathing, struggle to maintain rhythm, and feel overwhelming fatigue.

How to feel them: VT1 is marked by slightly harder breathing but you can still hold a conversation. VT2 is when you’re breathing very heavily and conversation becomes difficult. RCP is the point at which breathing becomes very heavy and rhythm is difficult to maintain.

How to boost them: Regular endurance training helps to improve VT1 and VT2. Individuals with higher cardiorespiratory fitness generally have higher VT1 and VT2 values. Be aware that heat and altitude can lower these thresholds.

Critical Power (CP): Your Sustained Power Limit

What it is: Your Critical Power (CP) is the highest power output you can maintain for a prolonged period without experiencing rapid fatigue. Think of it as the point where all the other thresholds are in a kind of steady state. If you exceed your CP, you’ll quickly accumulate lactate, struggle to get enough oxygen, and be unable to vent enough CO2.

How to feel it: When you exceed your CP, you’ll notice a significant increase in perceived effort, rapid breathing, and an overall feeling of fatigue.

How to boost it: Tempo running is key. By running just above your CP, you teach your body to endure an anaerobic response for longer. This pushes your CP higher, improving your ability to maintain higher intensities for longer.

The Best Training Approach: A Three-Pronged Strategy

Distance Runs (Long, Slow): These are your aerobic engine builders. They target your AeT, increasing your body’s ability to burn fat for fuel and improving your endurance.

Interval Training (HIIT): HIIT is your lactate-busting weapon. It improves your AT/LT, VO2 max, and lactate clearance, allowing you to work harder for longer.

Tempo Runs (Threshold Runs): Tempo runs are your CP enhancers. They train your body to endure at a higher intensity, pushing your critical power limit.

Kontender: Your Personalized Threshold Training Partner

Stop guessing and start training smarter. Kontender is the Apple Watch app designed to optimize your tempo runs and interval training using the power readings from your Apple Watch. Kontender tells you exactly when to run and when to walk to optimally stress your aerobic and anaerobic/lactate thresholds.

Recap: Your Path to Running Mastery

• Aerobic Threshold (AeT): Boost your endurance with long, slow runs, training your body to burn fat more efficiently.
• Anaerobic/Lactate Threshold (AT/LT): Increase your capacity for high-intensity work with HIIT and the Norwegian model of threshold training.
• Ventilatory Thresholds (VT1/VT2): Train consistently and monitor your breathing as a guide to your intensity.
• Critical Power (CP): Improve your sustained power with tempo runs just above your CP.

Ready to take your running to the next level? Download Kontender today and start training smarter, not harder. Your best runs are ahead of you.