Every threshold in our calculators traces to a published study. Here they all are — PubMed links, what each one actually found, and where we use it. If a claim on this site can't be traced to this page, call us on it: glen@cozyriverstudios.com.
Søberg S, et al. "Altered brown fat thermoregulation and enhanced cold-induced thermogenesis in young, healthy, winter-swimming men." Cell Reports Medicine, 2021.
The source of the "11 minutes per week" target. Winter swimmers averaging ~11 min/week of cold immersion across 2–3 sessions showed enhanced brown-fat activity and cold adaptation versus controls.
Read on PubMed → · Used in: Cold Plunge Calculator
Buijze GA, et al. "The effect of cold showering on health and work: a randomized controlled trial." PLOS ONE, 2016.
~3,000 participants; adding a 30–90 second cold finish to daily showers reduced self-reported sick-day absence by 29%. Notably, 30 seconds performed as well as 90.
Read on PubMed → · Used in: Cold Plunge vs. Cold Shower
Roberts LA, et al. "Post-exercise cold water immersion attenuates acute anabolic signalling and long-term adaptations in muscle to strength training." Journal of Physiology, 2015.
Twelve weeks of lifting with post-session cold immersion produced smaller gains in muscle mass and strength than active recovery — the basis for keeping cold 4–6+ hours away from strength work.
Read on PubMed → · Used in: Cold Plunge After a Workout
Tipton MJ, et al. "Cold water immersion: kill or cure?" Experimental Physiology, 2017.
The standard review of cold-water physiology: cold shock, autonomic conflict, and afterdrop — why our calculator caps session times and why "colder and longer" is the wrong instinct.
Read on PubMed → · Used in: Cold Plunge Calculator
Šrámek P, et al. "Human physiological responses to immersion into water of different temperatures." European Journal of Applied Physiology, 2000.
The study behind the popular cold-and-dopamine claim. One hour of head-out immersion at 14°C (57°F) sharply raised noradrenaline via sympathetic activation. The widely-quoted "+250% dopamine / +530% noradrenaline" figures trace to this single small study and are often overstated online — the noradrenaline/alertness effect is solid; treat the dopamine magnitude as suggestive, not settled.
Read on PubMed → · Used in: Cold Exposure & Dopamine
Laukkanen T, et al. "Association between sauna bathing and fatal cardiovascular and all-cause mortality events." JAMA Internal Medicine, 2015.
The Finnish cohort (~2,300 men, 20+ years): 4–7 sauna sessions/week associated with substantially lower cardiovascular and all-cause mortality vs. 1×/week; sessions ~19+ minutes at ~174°F showed the strongest association.
Read on PubMed → · Used in: Sauna Calculator
Laukkanen T, et al. "Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men." Age and Ageing, 2017.
Same cohort: 4–7 sessions/week associated with ~65% lower risk of Alzheimer's disease vs. 1×/week. Association, not proof of causation — but dose-consistent with the cardiovascular findings.
Read on PubMed → · Used in: Sauna Calculator
Tei C, et al. "Waon therapy for managing chronic heart failure." Circulation Journal, 2016 (multicenter randomized WAON-CHF study).
The clinical evidence that lower-temperature infrared heat (~140°F) produces meaningful cardiovascular effects — the reason our calculator credits infrared sessions at an adjusted dose rather than zero.
Read on PubMed → · Used in: Infrared vs. Traditional
Scoon GS, et al. "Effect of post-exercise sauna bathing on the endurance performance of competitive male runners." Journal of Science and Medicine in Sport, 2007.
Three weeks of post-run sauna (~30 min, ~194°F) increased run time-to-exhaustion ~32% and plasma volume ~7% in competitive runners — the heat-acclimation case for endurance athletes.
Read on PubMed → · Used in: Sauna After Running
Hamblin MR. "Mechanisms and applications of the anti-inflammatory effects of photobiomodulation." AIMS Biophysics, 2017.
The standard mechanism review: how 600–850nm light interacts with cellular targets, and why the dose-response is biphasic — the basis for our calculator's "past ceiling" verdict.
Read on PubMed → · Used in: Red Light Dose Calculator
Zein R, Selting W, Hamblin MR. "Review of light parameters and photobiomodulation efficacy: dive into complexity." Journal of Biomedical Optics, 2018.
Why irradiance, distance, and time — not device marketing — determine outcomes. Source for treating J/cm² (irradiance × time) as the unit that matters and for goal-specific dose windows.
Read on PubMed → · Used in: Red Light Dose Calculator
Leal-Junior EC, et al. "Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis." Lasers in Medical Science, 2015.
Meta-analysis finding pre-exercise phototherapy improved performance and recovery markers — the strongest sports-recovery evidence in the category, with doses in the ranges our calculator uses for muscle.
Read on PubMed → · Used in: Best Red Light Panels
Konrad A, et al. "The acute effects of a percussive massage treatment with a Hypervolt device on plantar flexor muscles' range of motion and performance." Journal of Sports Science and Medicine, 2020.
Five minutes of percussive treatment acutely increased range of motion without reducing strength — representative of the evidence: real short-term ROM/soreness effects, no grand recovery claims.
Read on PubMed → · Used in: Best Massage Guns
How we read evidence: cohort studies show association, not causation; small trials need replication; and "no evidence yet" is different from "disproven." Where the literature is thin — most of consumer recovery tech — we say so on the page instead of rounding hype up to fact. None of this is medical advice.
