Short answer: A shower and an immersion tub are different exposures. Evidence does not establish one as universally better or allow their temperatures and durations to be treated as equivalent.
Comparison framework
| Factor | Shower | Immersion |
|---|---|---|
| Measurement | Spray temperature and coverage may vary | Water temperature, depth, and setup can be documented |
| Infrastructure | Existing plumbing and slip-safe exit | Container, drainage, water care, installation, supervision, exit |
| Protocol transfer | Do not convert a shower time into an immersion dose or vice versa | |
Safety limits
Neither format removes cold-shock, fall, cardiovascular, breathing, or impaired-exit concerns. Do not hyperventilate or hold the breath in or near water. Equipment instructions, symptoms, health context, supervision, and a reliable exit control.
Bottom line: Compare setup and safety requirements; do not name a universal winner or publish a generic dose.
Evidence and limits
Cold-water research uses different populations, temperatures, depths, durations, and outcomes. It does not establish a universal home protocol or general-health result.
Sources: health and wellbeing systematic review; post-exercise recovery systematic review; National Weather Service cold-water safety.