A single-body plunge held at four degrees, filtered and still. Entry is measured, not endured — you go in on the exhale and hold to the count.
What it does
Held at a constant 4°C
Guided entry on the exhale
Counted holds, no bravado
Warm floor and towel at the exit
The reading
Temperature
4°C
Duration
15 min
Protocol
3 immersions, 15 min. 60–90 sec each at 4°C, full re-warm between. Nasal breathing throughout.