Boost Your Fitness: How to Find Your Anaerobic Threshold on a Treadmill!

Greg Rainbolt
Jun 3
5 min read

The anaerobic threshold (AT), often called lactate threshold, is the exercise intensity at which your body shifts from primarily aerobic energy production to anaerobic, leading to a rapid increase in lactate buildup. For runners, this typically occurs at 70–85% of your maximum heart rate (MHR). Knowing your AT helps you train more effectively by identifying the pace or heart rate at which you can sustain high-intensity efforts without fatiguing quickly—perfect for your audience of fitness enthusiasts looking to improve performance and prevent overtraining.

Step-by-Step Instructions for an Anaerobic Threshold Test on a Treadmill

What You’ll Need

• A treadmill with adjustable speed and incline.

• A heart rate monitor (chest strap preferred for accuracy, but a smartwatch can work).

• A stopwatch or timer (most treadmills have built-in timers).

• A notebook or app to record data.

• Optional: A partner to assist with recording data or adjusting the treadmill.

• Optional: A blood lactate meter (for lab-grade accuracy, though not required for field testing).

Preparation

1. Ensure Safety and Readiness:

• Confirm you’re in good health for high-intensity exercise. If you have medical conditions (e.g., heart issues), consult a doctor first.

• Wear proper running shoes and comfortable workout clothes.

• Hydrate well, but avoid eating a heavy meal 2–3 hours before the test. A light snack (e.g., a banana) 30–60 minutes prior is fine.

• Perform this test on a day when you’re well-rested, not after a hard workout.

2. Warm Up (10–15 Minutes):

• Start with a 5-minute walk at 3.0–3.5 mph (4.8–5.6 kph) with a 0% incline to loosen up.

• Transition to a 5–10-minute easy jog at a pace you can comfortably hold while talking (e.g., 5.0–6.0 mph or 8.0–9.6 kph, depending on your fitness level), still at 0% incline.

• Your heart rate should be around 50–60% of your MHR (calculate MHR as 220 minus your age; e.g., for a 40-year-old, MHR = 180 bpm, so 50–60% is 90–108 bpm).

3. Set Up Your Equipment:

• Ensure your heart rate monitor is working and synced to your device.

• Set the treadmill to a 1% incline to mimic outdoor running conditions (wind resistance).

• Have your notebook or app ready to record your heart rate, speed, and perceived exertion every few minutes.

The Test: Incremental Treadmill Protocol

This method involves gradually increasing your pace until you reach a point where you can no longer hold a conversation comfortably, indicating you’ve crossed your AT. It’s a field test that doesn’t require a lab but still provides a good estimate.

1. Start at a Moderate Pace (3 Minutes):

• Begin running at a pace that feels moderately challenging but sustainable—around 65–70% of your MHR. For most people, this might be 6.0–7.0 mph (9.6–11.3 kph), depending on fitness level.

• Run for 3 minutes at this pace with a 1% incline.

• At the end of 3 minutes, note your heart rate and your Rate of Perceived Exertion (RPE) on a scale of 1–10 (1 = very easy, 10 = maximum effort). At this stage, your RPE should be around 4–5, and you should still be able to talk in full sentences.

2. Increase Speed Gradually (Every 3 Minutes):

• Increase the treadmill speed by 0.5 mph (0.8 kph) every 3 minutes. For example, if you started at 6.5 mph, go to 7.0 mph, then 7.5 mph, and so on.

• Keep the incline at 1% throughout.

• After each 3-minute stage, record your heart rate and RPE. Also, perform the “talk test”: Can you still speak comfortably? Around your AT, you’ll start to struggle to say more than a few words without pausing for breath (RPE around 7–8).

3. Identify Your Anaerobic Threshold:

• Continue increasing speed every 3 minutes until you reach a point where you can no longer speak comfortably (e.g., you can only say 2–3 words at a time before needing to breathe). This typically happens at 70–85% of your MHR (e.g., 126–153 bpm for a 40-year-old with an MHR of 180 bpm).

• Your RPE will likely be 7–8, and you’ll feel a noticeable increase in breathing effort and leg fatigue.

• The speed and heart rate at this stage are your estimated AT. For example, if you reach this point at 8.5 mph with a heart rate of 145 bpm, that’s your AT pace and heart rate.

4. Cool Down (5–10 Minutes):

• Once you identify your AT (or if you can’t continue due to fatigue), reduce the treadmill speed to a slow jog (e.g., 4.0–5.0 mph) for 3 minutes, then walk at 3.0 mph for another 3–5 minutes.

• Stretch your calves, quads, and hamstrings to prevent stiffness.

Optional: Blood Lactate Testing (Lab-Grade Accuracy)

If you have access to a blood lactate meter (e.g., Lactate Plus), you can measure lactate levels for a more precise AT:

• During each 3-minute stage, pause briefly (10–15 seconds) to prick your finger and measure lactate.

• AT typically occurs when lactate levels rise above 4 mmol/L, often showing a sharp increase between stages (e.g., from 2.5 mmol/L at 7.5 mph to 4.2 mmol/L at 8.0 mph).

• This method is more accurate but not necessary for most people—heart rate and the talk test are sufficient for a field test.

Analyze Your Results

• Heart Rate at AT: The heart rate at which you could no longer speak comfortably (e.g., 145 bpm) is your AT heart rate. Use this to set training zones:

• Below AT (aerobic zone): 60–70% of MHR (e.g., 108–126 bpm) for endurance.

• At/near AT (threshold zone): 70–85% of MHR (e.g., 126–153 bpm) for tempo runs.

• Above AT (anaerobic zone): 85–100% of MHR (e.g., 153–180 bpm) for intervals.

• Pace at AT: The speed at which you hit your AT (e.g., 8.5 mph) is your threshold pace. Use this for tempo runs to improve endurance.

• RPE Insight: Your RPE at AT (around 7–8) can help you gauge intensity without a heart rate monitor in future workouts.

Apply to Your Training

For your Thrive Tribe audience, explain how to use these results:

• Endurance Runs: Spend most of your running time below your AT (e.g., 60–70% of MHR) to build an aerobic base and prevent overtraining.

• Threshold Workouts: Do 20–30-minute tempo runs at your AT pace/heart rate (e.g., 8.5 mph or 145 bpm) once a week to improve stamina.

• Interval Training: Add high-intensity intervals above your AT (e.g., 1-minute sprints at 90% MHR, followed by 2-minute recovery jogs) to boost speed and power.

Safety Tips and Considerations

• Listen to Your Body: If you feel dizzy, overly fatigued, or experience chest pain, stop immediately and seek medical advice.

• Progress Gradually: If you’re new to high-intensity running, start with shorter intervals (e.g., 1-minute stages instead of 3) to avoid injury.

• Hydration and Recovery: Drink water after the test, and avoid scheduling another intense workout for at least 24–48 hours.

• Treadmill Safety: Familiarize yourself with the treadmill’s emergency stop button, and keep a firm grip on the handrails if needed during speed changes.

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