[petodo]

I can do about 2:36 when I tried it recently sitting at kitchen table, zero preparation besides few deep inhales/exhales.

I remember without any preparation in past I could do 50-70 seconds, so I was blown away by 2.5 minutes after many years, do those few deep inhales/exhales prior holding breath make that much difference?

I am not doing any sport or exercise, at best like <5mins per day, just walk everywhere and sit at computer most of the day.

[DiggyJohnson]

Yes, it’s crucial in fact.

[petodo]

I remember reading about it, but care to explain simply why it helps?

[TamDenholm]

Not an expert but my basic understanding is that the hyperventilating before holding your breath basically oxygenates your blood so that you can hold for longer.

[postsantum]

No, that's because hyperventilation washes out CO2 so the CO2 alarm going off later than usual