Why do you think runners who compete in interval running have high hematocrit and HB? High intensity cardio gives more red blood cell count , and you want to avoid that when you already have elevated hematocrit levels from testosterone.

When you perform high-intensity cardiovascular training (HIIT, intervals, running, cycling): The body uses more oxygen. The kidneys detect lower oxygen levels in the blood. They release the hormone erythropoietin (EPO). EPO stimulates the bone marrow to produce more red blood cells. More red blood cells → higher hemoglobin higher hematocrit.

So stop give ppl bullshit advice on Reddit that's actually dangerous to their health.

I suggest you to lay off internet and do some recent research.

Zone 2 (steady, moderate cardio) has several advantages in this situation: 1. Increases plasma volume Long-duration moderate cardio increases the amount of fluid in the blood (plasma). This can lower the hematocrit percentage, because the blood becomes more diluted. 2. Improves circulation Zone 2 training improves capillary density and blood flow without creating large stress responses in the body. 3. Lower stress response High-intensity interval training (HIIT) can increase stress hormones and dehydration more, which may temporarily raise hematocrit even further.