For 45 years, Austinites have headed to Barton Springs Pool on the first day of the year for the Polar Bear Plunge. In collaboration with the Save Our Springs Alliance, the event raises money and awareness to preserve the Austin landmark. It's also a chance to wash off the languor of the holidays and find a sharp new sense of rejuvenation in the pool's 68-degree (F) waters.
Dr. Jessica Tranchina, a physical therapist and CEO of the Generator Athlete Lab Downtown, explained that while cold plunging - or brief immersions in water between 50 and 70 degrees - can sound scary, it has a variety of short- and long-term health benefits.
"You feel like you're fighting the bear," Tranchina says. "It activates what we call the sympathetic nervous system, known as the fight or flight [response]."
The body responds to the cold temperatures with a rush of exciting, feel-good hormones including dopamine, serotonin, endorphins, and norepinephrine.
"The more you consistently do cold plunging, the higher your threshold and levels of dopamine in your body," Tranchina says. "So even when you're not cold plunging, or you didn't cold plunge that day, you feel more focused."
Cold plunge enthusiasts point to heart benefits as well. When plunged into frigid water, the body constricts blood flow to the core. Then the blood pumps back out through arteries and veins when exposed to warmth. (Note: Cold plunges are not generally recommended for people with heart conditions or other medical conditions.)
"It's like flexing the muscles of your vascular system," she says.
Similarly, a polar plunge can help remove toxins and damaged tissues from the body by activating both the lymphatic system and the immune system, Tranchina said.
"You release white blood cells in this proportion when you're sick," she says. "The only other time that [white blood cells] are released in this quantity is in a cold plunge - which is basically hacking your body."
If you want to start the new year off with a splash, or need some mental clarity after a spirited New Year's Eve, then come "fight the polar bear" and experience the surge of adrenaline yourself.