How to increase tolerance to cold water

I went for a run by the beach this morning and finished by getting in the ocean. It was 8am and the water felt piercingly cold. I didn't last more than 7 minutes. Surprising because water temperature in October is almost at the high of the year and also because I've been taking cold showers for over 600 days straight.

My first thought was "K Camp is over; there's no way I can endure four hours of this!" In another post, I mention how frightened I am about surf torture.

I did some non-exhaustive research in the afternoon and found that there is hope. It's possible to build resistance to cold water. I couldn't find a scientifically proven method to do it, but there are enough bits and pieces to concoct a plan.

A couple of scientific papers:

15 months of military training

In a study conducted in northern Sweden, researchers found that the ability to rewarm the body after prolonged exposure to cold water significantly increased post-training. The test was conducted in 45 men. (Aviation, Space, and Environmental Medicine, 2008 Sep).

Biohack: ephedrine-caffeine.

A mixture of ephedrine-caffeine (1mg/kg - 2.5mg/kg) was administered to subjects during seminude exposures to cold air (3 hours at 50°F). The drug ingestion reduced the total drop in core, skin, and body temperatures. The mixture achieved this by means of increasing energy expenditure by almost 20%; in other words, cold tolerance was not enhanced by an increased conservation of heat but by a greater energy expenditure. (Journal of Applied Physiology, 1989 Jul).

I wonder if caffeine alone would do. I don't see why not.

Now, a few pointers from a Kokoro Camp graduate, and from an article written by a cold water distance swimmer.

Get fat

A little bit of extra weight helps considerably in insulating the core from the cold. Even a 5lbs increase in weight can make a difference. I'll shoot for 10lbs for Kokoro.

Get fit

Be capable of generating more body heat by moving/swimming harder and faster.

Cold baths and ocean swims

A recent Kokoro Camp graduate told me that, during his preparation, he would fill in the bathtub with water and ice, and then jump in for 20 minutes. Every Friday night. And on Saturdays, he would go for a swim in the ocean until his body was numb. The body will adapt to the cold water after a while.

Stay focused

During surf torture, you have to endure numbness, a clattering jaw, uncontrollable shaking, bone pain. A terrifying combination of symptoms that convinces you that you are in serious danger. Just remember: the instructors will not let you die. Keep pushing forward.

The summing up: the only easy day was yesterday; pain is coming.

P.S.: sleep deprivation
Scientists tested the effects of 29 hours of sleep deprivation on cold tolerance. It's similar to K Camp in the sense that sleep deprivation is a constant factor. Well, no surprise, the study found that cold tolerance is much weaker with a sleep-deprived body than with a well-rested one. Damn. (European Journal of Applied Physiology, 2012 Sep).