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Bolt test

🎯 Let’s start with a little test

All instructions are provided in the videos.


BOLT is an acronym that stands for Body Oxygen Level Test. It is a light breath hold test. Light meaning you don’t try to hold your breath for as long as you can, but only until you feel the first distinct desire to breathe.

  • Lean back or lie down in a relaxed position.
  • Take a normal inhale and normal exhale.
  • Pinch your nose, hold your breath and start the timer.
  • At the first clear sensation of wanting to breathe, stop the timer and inhale through the nose.

Breathing should continue normally, not gasping for air. If you push the breath hold too far to breathe normally at the end, look for an earlier sensation next time.


Now that you know how to measure your BOLT score, try to get into the habit of checking it every morning. If you are less interested in looking at daily variation and more interested in long term progress, do this test once a week.

If for any reason you don’t like the BOLT score as a measurement, there is another test for you to try.

Carbon Dioxide Tolerance Test

Similar to the BOLT score, it ALSO measures the efficiency of your breathing system and the long term progress of it, as well as short term variation in how rested and recovered you are. The CO2 Tolerance Test is basically a few big breaths, followed by a maximum length exhale. Again, you’ll need a timer.

What you do is take a big breath in through the nose – (inhale) – and relax to allow the air out – (exhale). And just repeat this four times. Take four big breaths.

After those four, you take a fifth inhale, filling your lungs all the way, and start the clock as you exhale as slow and for as long as you can, breathing out through your nose. Keep a constant flow of air coming out and measure how long you can continue that.

Stop the timer when you run out of air – or you have to take a breath in.

This measures your CO2 Tolerance and your diaphragm control, which are good metrics for how your whole breathing system is functioning.

The first goal here is to get to at least a minute, or if you want to set the bar high, two minutes. And again, you’ll get the best results in a rested state, in the morning, on an empty stomach. For example, if you get only 20 seconds now, it might be 35 in the morning.

The CO2 Tolerance Test and the BOLT score correlate well with each other. In other words, since they measure the same thing in different ways, there’s no need to do both of them.

Just pick one that you like and use it every week to gauge your progress, or every morning to help you decide whether it’s a good day for heavy exercise or rest, or something in between.

Personally, I prefer the BOLT score because it’s easier – it takes less time and has less of a skill component. The same exercises that increase the BOLT score will increase the CO2 Tolerance Test.

📝 Instructions

  • Lean back or lie down in a relaxed position.
  • Take a large inhale through the nose, and let the air out in a relaxed exhale.
  • Repeat a total of four times.
  • On the fifth inhale, fill your lungs all the way.
  • Start the timer and breathe out through your nose as slow and as long as you possibly can.
  • Stop the timer when there is any interruption in the continuous exhale.