Counterpressure is a way to quickly, temporarily increase your blood pressure to stave off the fainting that comes with low blood pressure light-headedness https://my.clevelandclinic.org/-/scassets/files/org/heart/disease-conditions/syncope/counter-pressure-techniques-1014.ashx?la=en

If this is what your body is doing, you will feel the results of counterpressure within seconds