How to Conduct a Personal Experiment: Cold Water Plunges

I’ve always been a self-experimenter, even when I didn’t realize it. Back when I raced competitively, I logged – compulsively – all my training routes, times, and distances. My logging didn’t begin as a grand self-experiment. It was just a way to authenticate my hard work. See, races were their own reward. Beating the other guys? Nothing sweeter. But those were few and far between. To get to those races, I had to train, day in and day out, with nothing tangible to show for it save for sore joints and a bottomless pit for a stomach. Filling those blank spaces with numbers made what I’d done somehow tangible, and the agony of training day in, day out became more bearable.

Of course, patterns emerged in those logs. I’d notice a string of particularly strong training days and think to myself, “What was different that week?” Had I eaten a particular something? Had I not eaten a particular something? If a weak sequence appeared, I’d wonder the same thing and explore my past. “Oh yeah, that was the week I had friends in town and I stayed up late every night” – maybe sleep does matter! Or, “I trained fewer days that week and my times actually improved” – could less possibly be more? And so from the practical, the numbers, the data, the objectivity, I gleaned the intuition, the insight, the lessons to be learned.

Now that I’ve internalized all those training lessons learned from my accidental self-experimentation, I don’t have to log it. I just do it. Same goes for eating. I don’t calorie or carb or protein count; I just eat. You can get there, too, and I suspect many of you have with regards to certain aspects of your diet or your training. But before you get there, before you’re dialed in, you have to experiment. You have to start with an idea, give it an honest shot, and see it through to the end. Though making your experiment air-tight enough to pass peer review isn’t necessary, try to be as systematic and scientific as you can. It will pay off and your results will have that much more meaning.

I hear people getting up to leave. I know, I know. We’re all about the ease of Primal eating, exercising, and listening to one’s body while looking at calorie-counting with suspicion and often barely veiled scorn – “just follow these basic rules and everything will fall into place like so” –  but logging data, analyzing data, and drawing conclusions from said data is really about honing your intuition. It’d be nice if we all maintained that Primal connection to our bodies, but most of us have not. Most of us have lived lives divorced from our bodies, eating weird pseudo-foods, strapped several inches of rubber to our feet, sitting in the same place for ten hours a day, staring at one electronic screen or another instead of the wide world around us, sleeping in rooms with bright blue green blinking shards of light filling our dreams, and we’re all a little confused. That’s okay. That’s to be expected. We can come back from this to reclaim our intuition, and data logs, journals, and self-experiments are how we get there.

You know how people say you go to college to learn how to learn? This is kinda like that.

What’s cool is that we can all learn something from a self-experiment. No matter what you know or think you know, you have a weak spot that can be identified and hammered out by systematically logging, journaling and testing. I know this because I have plenty of them myself. Ever since I wrote that first post on self-experimentation, I’ve been playing around with my own experiments, and I have an effective, simple methodology for testing. Also since that blog post I’ve quietly been putting the finishing touches on a new book, a 90-Day Primal Journal that will contain this methodology and deals with precisely this subject. It drops later this month.

Thus, this post marks the start of a new self-experimentation series on MDA. In the coming weeks, I’ll introduce new concepts to try, parameters to track, and experiments to run, but today, we’re going to cover cold water plunges.

Why cold plunges? A few reasons. First, cold water immersion is sort of a hot topic these days around the Primal and ancestral health community. It’s on people’s minds, so they’re already primed to consider it. If I had just come out of the blue with a random charge – “try plunging your mostly-naked body into cold water!” – you might write me off. This way, it’s not such a foreign concept.

Second, the weather’s warming up (at least for those of us living where summer is approaching). You’re more likely to try something as physically unappealing and discomforting as a cold plunge when it’s warm out. When it’s cold out? Not so much. For many people, the winter months are traditionally associated with hot mugs of coffee, hearty soups, and raging fireplaces, not feed troughs full of hose water doubling as immersion baths. This is a good time to ease into the practice of plunges. And who knows – maybe you’ll dig ’em so much that you consider employing them in winter, too.

Third, for all the negative (and positive) stuff surrounding cold plunges, I think there’s real merit in them. They aren’t faddish, they aren’t (necessarily) dangerous, and though they’re not magical, brief exposure to cold can serve as a potent hormetic stressor that can induce positive adaptations.

Fourth, I’ve been incorporating them into my own routine for a few years now, and I’ve noticed a big difference. I think you guys will, too, and I think a community-wide push to systematically test the effect of cold plunges will give us a lot of data.

Okay, so how do I do it?

Come up with a goal that cold plunges may help realize. The link between your goal and the plunges should be plausible, of course. People make a lot of fantastical claims about the benefits of cold water plunges. Some say it’ll make you immune to the ravages of even the most pernicious pathogens. Some folks claim that cold water plunges will fine tune your metabolism. And some people swear that there’s no better hangover cure than a few minutes in some really cold water. While I have little doubt that there are kernels of truth hidden within most of these claims, the bulk of the established research has hitherto focused on workout recovery and fat loss.

Here are a couple ideas, but you can definitely come up with your own:

  • I want to improve workout recovery.
  • I want to lose body fat.

Then, come up with a hypothesis:

  • Post-workout cold plunges will improve recovery, reduce soreness, and increase subsequent performance.
  • Daily cold plunges will reduce body fat without affecting lean mass.

Let’s choose “workout recovery.” Identify the variables and note how they may affect the outcome:

  • Water temperature – Is colder better? Is there such a thing as “too cold”?
  • Time spent plunging – Is five minutes better than three? Is there such a thing as “too long”?
  • Frequency – Every day or every other day?
  • Contrast – Is cold/hot contrast water immersion better?
  • Body parts immersed – Is full body necessary? What if I just stick the legs in? Do I need to dunk my head? Do I only need to dunk the body parts I just worked out?
  • Time of day – Does it matter how far post-workout I take the plunge?
  • Workout intensity and volume – The intensity and volume of the workout itself are obviously huge determinants of how well you recover.

Test one variable at a time. If you change more than one variable from one plunge to the next you won’t be able to attribute the positive or negative results to the accurate variable.

Then, decide what you’ll be measuring in order to quantify “workout recovery”:

  • Subjective perception of soreness, ranked 1-10.
  • Heart rate upon waking, indicative of “recovery.” Overtrained individuals will often wake with elevated heart rates.
  • Weight lifted, reps hit, sprint times, mile times, and other markers of performance.

Oh, and if you want really strong results, be sure to introduce a period where you remove the cold plunges and note the change (or lack thereof) in workout recovery.

There are inherent limits to this brand of personal science, but so what?

Again, you are not a team of objective scientists, slavishly eliminating confounding variables (or trying your best) to test a single, solitary change and get published. You’re the scientist, the subject, and the reviewer. Ultimately, you’re just trying to help yourself and improve your health, not get published. You can cut corners. You won’t be able to eliminate confounders. Your diet won’t be completely static throughout, nor will your workouts, or the weather, or your sleep, or your stress levels. Things may have changed without the introduction of the variable, since working out consistently will generally produce improved performance, with or without a cold plunge. These things and more will affect the results of what you test, but that’s okay. After all, that’s life.

Okay. I’ve said my piece. Now, it’s your turn to get out there and get into some cold water. Shoot for around 60 degrees F, which will feel cold but not shockingly so. Stay in for as long as you can handle to start. Be sure to let me know how it goes!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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