Float blog

My 30-day float challenge

6.4 to 2.0 in four weeks.

Note; this is an update from a blog I wrote in July 2025. Since then I did a 30 day float challenge and learned more about how inflammation works with floating so an update was needed.

That’s my hs-CRP, the blood marker doctors use for inflammation. I started in the range cardiologists flag as high risk. Thirty days of floating later, I was back in the average range. Here’s what happened, and the science that explains it.

6.4mg/L before. High-risk range.
2.0mg/L after 30 days. Average range.
Float therapy at Float Boston in Somerville

The short version

I own a float center, so you should be skeptical of me. I was skeptical too. So I ran the test on myself: bloodwork, 30 days of floating, bloodwork again.

My hs-CRP fell from 6.4 mg/L to 2.0. That’s a 69% drop. Anything over 3.0 is considered high risk for heart disease, and I was at more than double that. With heart trouble in my family, that got my attention. My heart rate variability rose 33% and my restorative sleep went up 43% over the same four weeks.

I’m one person, not a clinical trial. But my numbers line up with what researchers have been finding about stress, inflammation, and what happens when your nervous system finally gets a break.

Mark, owner of Float Boston

Why a float tank can move a blood test

It sounds like a stretch. Lie in salt water, change your bloodwork. The link between the two is stress.

The problem

The fire that never goes out.

Inflammation isn’t the enemy. It’s how your body heals a cut or fights a cold. It switches on, does the job, and switches off.

The trouble is the kind that never switches off. Chronic, low-grade inflammation simmers for months or years with nothing to fix. You usually can’t feel it directly. You feel what comes with it: stiff joints, slow recovery, poor sleep, and being tired for no clear reason.

Doctors measure it with a blood test called hs-CRP. Under 1.0 mg/L is low risk for heart disease. Between 1.0 and 3.0 is average. Over 3.0 is high.

I was at 6.4. I felt fine. That’s the scary part.

It’s scarier for me than for most. Heart trouble runs in my family. My mom had a cardiac arrhythmia, and I have a family history of heart failure. This is exactly the number I’m supposed to be watching, and it was more than double the high-risk line.

The fuel

Stress keeps it burning.

Most people blame diet, and diet matters. But one of the biggest drivers is one we rarely treat: stress.

Cortisol, your main stress hormone, is also the signal that tells inflammation to stand down. Under constant stress, your immune cells stop listening to it. A Carnegie Mellon team showed this in 2012: people under prolonged stress lost the ability to regulate their inflammatory response.

So the question isn’t only what you eat. It’s whether your nervous system ever gets a real break. For most of us, the honest answer is no.

The tank

An hour with nothing to react to.

A float tank takes away almost everything your nervous system has to process. No light. No sound. No gravity to fight. Water at skin temperature, so you lose track of where your body ends. With nothing to react to, your body drops out of fight-or-flight on its own.

The research on that is solid. In a 2018 study, 50 people with anxiety and stress disorders did a single 60-minute float. They reported significant drops in stress, muscle tension and pain, and the most stressed people got the biggest effect. A second study that year tested floating against a comparison condition in 31 people. Floating won on anxiety, muscle tension and relaxation.

My 30 days

I wanted numbers, not a feeling.

So I got bloodwork before I started, tracked my sleep and heart rate variability the whole way through, and tested again at the end.

That first number stopped me. It’s a blood test, not a mood. I went from more than double the high-risk line to comfortably under it, in four weeks, without changing anything else on purpose.

The other two numbers tell the same story. HRV measures how well your nervous system recovers from stress, and mine rose 33%. My restorative sleep went up 43%. It was the deepest sleep I’ve had in years.

Better sleep and a calmer nervous system are two of the strongest levers on inflammation there are. Floating gave me both.
Heat & cold

Contrast therapy works the same marker.

Floating comes at inflammation from the stress side. Contrast therapy, a sauna followed by a cold plunge, comes at it from the body side.

The best evidence is for heat. Finnish researchers studied 2,269 men and found that those who used a sauna four to seven times a week had hs-CRP readings 0.84 mg/L lower than men who went once a week. That’s the same marker that dropped for me.

A later study of the same group followed 2,575 men for almost 28 years. High inflammation raised the risk of dying early, and frequent sauna use appeared to offset it.

Our contrast suite is private and fits two people: a 160°F sauna and a cold plunge at 52 to 54°F. The two pair well with floating. Heat and cold to work the body, then a float to shut the stress response all the way down.

Run your own experiment

You don’t have to take my word for any of this. That’s the point. Here’s how to do what I did:

  1. Get a baseline. Ask your doctor for an hs-CRP test. It’s a common, inexpensive blood test. Don’t test while you’re sick, because a cold will spike it.
  2. Track something daily. If you wear a watch or a ring, write down your HRV and sleep numbers before you start.
  3. Float on a schedule. Put your floats on the calendar for 30 days and treat them like appointments.
  4. Add heat and cold if you want more. A contrast session between floats works the body side of the same problem.
  5. Test again. Same lab, same time of day, 30 days later. Then look at your own numbers.

One float is a nice afternoon. A practice changed my bloodwork.

I didn’t expect a number like 6.4. I felt fine. Most people walking around with high inflammation do. With my family’s history, I couldn’t ignore it. And I didn’t expect 2.0 four weeks later either.

I can’t promise you my results. I can tell you they’re real, they came from a lab, and the only thing I changed was getting in the tank.

Find out what your number does.

Float Boston is at 515 Medford Street in Somerville, open every day from 7:30 a.m. to 9 p.m.

Book your first float Take the 30-day challenge

Use code firstfloat to get half off your first float or couples float. Want to try heat and cold? Your first contrast therapy session is $50 with code love2sweat.

Floating and contrast therapy are wellness practices, not medical treatments, and nothing here is medical advice. The results described are one person’s experience and are not a promise of yours. The studies cited were conducted independently and their authors are not affiliated with Float Boston. Talk to your healthcare provider about any medical condition or test result.