YOUR OXYGEN BASE. READY OR NOT? THESE TWO TESTS WILL TELL YOU THE TRUTH!

I wrote about how to build an aerobic base, how important it is for endurance training, but how can we check whether we have already built this base and how strong it is?

According to Scott Johnston, you don't need a lab to test this. What's more, Johnston often "prefers field testing over lab testing," especially when determining the anaerobic threshold, because labs often "fly" through the zones too quickly, which skews the results.

However, it is sometimes very difficult for amateurs to perform these tests correctly without supervision, so a laboratory that measures lactate concentration in the blood is not a bad idea at all.

What do you need to do?

Identify two key physiological thresholds:

1️⃣ Oxygen Threshold (AeT) so-called "Down"

2️⃣ Anaerobic Threshold (AnT) so-called "Ceiling"

Then calculate the percentage difference between your thresholds. It should be less than 10% (meaning no ADS).

How to determine these thresholds?

You must perform TWO separate field tests several days apart.

Here is a step-by-step procedure based on Johnston's methodology:

Step 1 Determine your Oxygen Threshold (AeT) – "Down"

The most accurate home method that shows a very high correlation with blood gas tests is the Heart Rate Drift Test.

Execution

• Find a flat area or use a treadmill (best option for consistent conditions).

• After warming up, run for 60 minutes at a steady pace that feels aerobic to you (you can talk comfortably).

• Keep your speed constant, not your heart rate.

Calculation

• Compare your average heart rate for the first half of your run (minutes 10–30) with your average heart rate for the second half (minutes 30–60).

• If your heart rate increased by less than 5%, your average heart rate for this run is your Aerobic Threshold (AeT) or you are below it.

• If it increased by more than 5%, you were running too fast (above the threshold) – your AeT is lower.

Step 2 Determine Your Anaerobic Threshold (AnT) – The Ceiling

For this threshold, Johnston recommends a classic "time trial" which better reflects reality than short laboratory tests.

Execution

• After a good warm-up, run for 30 to 60 minutes (for amateurs, 30 minutes is usually sufficient, for elite runners 60 minutes).

• Run at the highest intensity you can sustain CONSISTENTLY throughout this time. This shouldn't be a sprint that "dies" after 5 minutes, but a sustained, powerful effort.

Result

• Your average heart rate from this effort (or the last 20 minutes if you're doing the 30-minute version to eliminate the heart-rate warm-up phase) is your Anaerobic Threshold (AnT).

Step 3 Calculate the difference

Once you have both numbers, do some simple math to see if you fall within the "healthy profile" (below 10%).

Examples of interpretation:

Scenario A (Healthy Profile / Good Base)

1. Your AnT (from the time trial) = 175 bpm.

2. Your AeT (from drift test) = 160 bpm.

3. Difference: 15 strokes.

4. Result: 15/175=8.5%.

   
   

Conclusion: You have a well-developed aerobic base. Your "lactate vacuum cleaner" is working efficiently at high speeds. You can incorporate more intensity into your training.

Scenario B (Anaerobic Deficiency Syndrome - ADS)

1. Your AnT (from the time trial) = 175 bpm.

2. Your AeT (from drift test) = 135 bpm.

3. Difference: 40 beats.

4. Result: 40/175=22.8%.

Application:

You have a huge "gap" in your fitness. Your body switches to burning sugars (anaerobic metabolism) at very low effort. You should focus almost exclusively on slow running (below 135 bpm) to push this lower threshold upward.

Fun fact:

Johnston notes that in elite cross-country skiers, this difference can be as little as 6% (e.g., 10 heartbeats difference between aerobic and anaerobic thresholds).

I hope you're increasingly understanding the importance of running below your aerobic threshold. Now, seriously, review your heart rate recordings from your runs and see what the difference is between your heart rate at the beginning and end of your run – calculate your "drift" and see if you're not exceeding your aerobic threshold.

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