Floatation therapy after heavy squats did not increase endorphin or enkephalin levels beyond what the workout itself produced, suggesting float tank relaxation isn't driven by opioid peptides.
No differenceFloatation therapy produced no significant change in beta-endorphin or proenkephalin levels compared to passive control recovery
What the researchers found
Floatation therapy (Float-REST) did not significantly change endogenous opioid peptide levels compared to a passive control recovery after heavy resistance exercise. Beta-endorphin (β-End) rose significantly after the intense squat workout in both conditions — as expected — but floatation therapy didn't produce any additional increase or differential pattern.
Proenkephalin (ProEnk), a precursor to the enkephalin family of opioid peptides, showed no significant changes in response to either the exercise or the floatation recovery. Its plasma levels remained detectable and stable throughout, suggesting it may function through local (paracrine) rather than systemic signaling.
The practical takeaway: the deep relaxation people commonly report from float tanks after exercise is probably not driven by changes in circulating opioid peptides. Beta-endorphin stayed consistently elevated from the workout itself regardless of recovery method.
Why it matters
Float tanks have become popular in athletic recovery, with many users reporting profound relaxation and reduced soreness. This study tested whether that relaxation is mediated by opioid peptides — the body's natural painkillers. The finding that it isn't means the subjective benefits of floatation likely come from other mechanisms (sensory deprivation, muscle relaxation, reduced cortisol) rather than an extra endorphin boost. This helps separate the science from the marketing around float therapy.
The numbers in context
n=11 · Trained men (squat 1RM: 153.1±20.1 kg) · 6×10 back squats at 80% 1RM · 1-hour float session · 5 blood draws over 48 hours · β-End significantly increased post-exercise (p≤0.05) · No differential effect of floatation · ProEnk stable throughout
How the study worked
Within-subject crossover controlled design. 11 resistance-trained men completed two exercise blocks separated by a 2-week washout. Each block involved the same high-intensity protocol (6 sets of 10 back squats at 80% of their one-rep max with 2-minute rest). After one session, they did a 1-hour float (Float-REST); after the other, a passive sensory-stimulating control. Blood was drawn at 5 timepoints: before exercise, immediately after, after recovery, 24 hours later, and 48 hours later. Beta-endorphin and proenkephalin were measured using ELISA immunoassays. Differences were assessed using repeated-measures ANOVA.
Who was studied
11 healthy resistance-trained men, mean age 22.5 years, with a strength-to-mass ratio of 1.8
What this study cannot tell us
Very small sample (n=11) of young, trained men limits generalizability. Only two opioid peptides were measured — other endogenous opioids (dynorphins, endomorphins) weren't assessed. The 1-hour float session is a specific protocol and different durations may have different effects. Subjective relaxation data wasn't correlated with peptide levels, so we can't directly test whether relaxation and peptide changes are dissociated. The study can't rule out localized opioid peptide changes in the brain that wouldn't appear in blood samples.
How to read the evidence
This is a well-designed crossover study with appropriate controls and methodology, but the sample size of 11 is small and limits statistical power. The study measures only two opioid peptides and can't assess central nervous system changes. Rated preliminary due to small sample and narrow scope.
When this study was published
Published in 2024 in the Journal of Strength and Conditioning Research. This is recent and represents current interest in evidence-based evaluation of popular recovery modalities.
The bigger picture
This study contributes to a growing body of research trying to understand why certain recovery modalities 'feel' effective. The finding that float tank relaxation isn't opioid-mediated shifts attention to other mechanisms — sensory deprivation effects on the nervous system, muscle unloading in salt water, or psychological components. It also adds to our understanding of how opioid peptides respond to exercise, confirming that beta-endorphin is reliably elevated by high-intensity resistance training.
Questions still open
- If opioid peptides don't explain float tank relaxation, what neurochemical changes (cortisol, GABA, serotonin) might be responsible?
- Would longer or repeated float sessions produce different opioid peptide responses?
- Does proenkephalin's lack of response to intense exercise mean it functions primarily through local rather than systemic signaling?
Common questions
Do float tanks increase endorphin levels?
If it's not endorphins, why do float tanks feel so relaxing?
Read the original research
Endogenous Opioid Peptides After Floatation Therapy in Resistance-Trained Men.
Journal of strength and conditioning research, 38(10), 1808-1812
Citation
Kraemer, William J; Caldwell, Lydia K; Post, Emily M; Volek, Jeff S; Hagen, Josh M; Newton, Robert U; Häkkinen, Keijo; Omonije, Oluseun; Maresh, Carl M. (2024). Endogenous Opioid Peptides After Floatation Therapy in Resistance-Trained Men.. Journal of strength and conditioning research, 38(10), 1808-1812. https://doi.org/10.1519/JSC.0000000000004931