Stupid, effective, free. Thirty seconds at the end of your normal hot shower, building to two minutes. No ice baths. No YouTube gurus. Just this.
Day 1 — 30s cold at the end.
Day 2 — 30s cold.
Day 3 — 45s cold.
Day 4 — Rest — warm shower.
Day 5 — 45s cold.
Day 6 — 60s cold.
Day 7 — 60s cold. Breathe slowly.
Day 8 — Rest.
Day 9 — 75s cold.
Day 10 — 75s cold.
Day 11 — 90s cold.
Day 12 — Rest.
Day 13 — 90s cold. Don't rush out.
Day 14 — 2 minutes cold.
Day 15 — Rest.
Day 16 — Start the shower cold — 30s, then warm, then end with 30s cold.
Day 17 — Same — 45s + 45s.
Day 18 — Rest.
Day 19 — Open cold, end cold — 60s + 60s.
Day 20 — 60s + 90s.
Day 21 — Rest.
Day 22 — Full cold for 2 minutes at start.
Day 23 — Full cold for 2 minutes at end.
Day 24 — Rest.
Day 25 — 3 minutes total cold (split as you like).
Day 26 — 3 minutes total.
Day 27 — Rest.
Day 28 — Entirely cold shower. 3+ minutes.
Day 29 — Entirely cold — 4 minutes.
Day 30 — Your choice. You've proven it.
Day 31 you can go back to warm showers. You won't want to. That's the joke.