Chiikawa Screams in the Cold Plunge, So Why Is Kurimanju Fine? | Anime Is Science - Video

Chiikawa, episode 49 ("Cold Bath / Citric Acid"). On the first trip to the sauna, Chiikawa steps into the cold plunge and instantly turns pale and screams. Kurimanju, meanwhile, sits in the same cold water with eyes closed, completely relaxed. Where does that difference come from?

Water conducts heat about 25 times better than air (thermal conductivity about 0.60 vs 0.025 W/m·K). Air at 15 °C (59 °F) is just a cool autumn day, but water at 15 °C pulls heat out of your body fast. The moment cold water hits your skin, you gasp without meaning to, and your heart races. That's the cold shock response, and it's strongest right as you get in. So Chiikawa's scream isn't fear. It's a reflex.

Does Kurimanju just not have that reflex? In a study at the University of Portsmouth in the UK (Tipton et al., 1998), people sat in 15 °C water for 3 minutes, six times. Their breathing in the first 30 seconds dropped from about 33 to about 20 breaths a minute. Their bodies had gotten used to the cold, and the effect was still there seven months later (Tipton et al., 2000).

One more thing: if you stay still in a cold plunge, the water right next to your skin warms up and forms a thin layer. Move, and that layer breaks, so the cold hits you all over again. That's why Kurimanju doesn't move a muscle. The scream is a reflex; the calm is practice.

???? Numbers we used
• Thermal conductivity at 20 °C: water about 0.60 W/m·K, air about 0.025 W/m·K, roughly 24x (we round to "about 25 times").
• Tipton MJ et al., Eur J Appl Physiol 1998: six 3-minute immersions in 15 °C water. In the first 30 seconds, breathing fell from 33.3 to 19.8 breaths/min and heart rate from 114 to 98 beats/min.
• Tipton MJ et al., Eur J Appl Physiol 2000: seven months later, the responses were still significantly reduced.

⚠️ Ease into a cold plunge feet first, slowly, and keep it short. If you have heart or blood pressure concerns, skip it.

Video, voice and music are our own AI-assisted creations. No original anime footage is used.

How many dips did it take you to get used to the cold? Tell us in the comments.

Anime really is science.
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