Morning CO2 Tolerance Test

A quick morning breathing check used as a low-cost marker of recovery and stress load. After waking, do several deep nasal inhales and full exhales, then take one deep nasal inhale and time a slow, controlled exhale until the lungs are empty; repeat under the same conditions each day for a more comparable reading. Longer times generally suggest better CO2 tolerance and may track with readiness, stress management, and overall recovery.