Christopher Ellis demonstrates a CO2 tolerance breath-hold test: exhale normally, pinch your nose, and time until you need to breathe. Holding for 15 seconds or less means high stress and poor recovery. 20-25 seconds or longer signals better nervous-system health and sleep quality.
If you're down to around 15 seconds or less, there's a lot of room for improvement, and that's a sign that your body's under stress. The next category is stress and nervous system, and this one greatly overlaps with sleep and recovery. If you're highly stressed, you're going to have poor recovery. So, the one simple test that I like to do is a CO2 tolerance test because when you are stressed, you're going to tolerate CO2 in the bloodstream less effectively. You basically take a couple regular breaths and at the end of an exhale, a regular exhale, not a max exhale, you pinch your nose closed and you time in seconds how long you can hold your breath. So basically you hold your nose closed, time it until something voluntary happens, like involuntary, sorry, like you swallow or you just have a sudden like air hunger, you need to breathe. And so ideally you can get in the 20 to 25 second range or better.
