Table 7.

Whole-body cold water immersion laboratory studies.

Reference	Study Sample	Habituation Length	Habituation Temperature	Cold Testing Procedure	Results/Findings
Lapp [92]	3 M, 5 F students	Cold water immersion 2x/week for 1 hr over 8 weeks	Reduced from 30°C to 21.1°C over 8 weeks	Longitudinal passive observation	↑ VO2 yet less frequently reported shivering in later weeks despite exposure to ↓ water temperatures
Radomski [93]	11 M; 3 M preadapted (PA) with immersion, 8 M non-preadapted (NPA)	9 daily immersions (20–60 min depending on tolerance) in cold water 20 days before Arctic exposure vs no immersion CON + 16 days in the Arctic	15°C immersion + Arctic (mean temperature −26.8°C)	Nude cold tolerance tests (10°C air for 1 hr resting supine) pre and post Arctic exposure	NPA: ↑ metabolism and Tre post Arctic exposure; ↑ urine volume (86%), urinary NE (48%), epinephrine (84%), and 17-hydroxycorticosteriods (34%) PA: ↔ metabolism and ↓ Tre; ↑ epinephrine (65%)
Young [96]	7 M	Daily 90 min cold water immersion 5 times/week for 5 consecutive weeks	18°C, wearing only swim trunks	Cold air stress test (CAST) pre and post acclimation program: 30 min rest at 24°C, 30% RH followed by 90 min in cold 5°C 30% RH air wearing only swim trunks	Post acclimation: ↓metabolism at 10 min of CAST but ↔ by 30 min, as such shivering onset delayed; Trec ↓ before and during CAST, and total drop in Trec during CAST ↑; Tsk ↓ and ↑ Tre – Tsk gradient; Larger ↑ in plasma NE
Bittel [97]	10 M	5 consecutive days/wk daily 1–3 h cold water immersion (to tolerance) over 2 months	10–15°C water; wearing neoprene diving suit	Standard cold test pre and post: 2 h supine on wire mesh bed wearing swimming trunks in 10°C air, wind speed 0.8 m/s, 40% RH	Post acclimation: ↑ in the delay for onset of shivering, ↓ Tb at onset of shivering, ↓ Tb in thermoneutrality, ↓ of heat debt by three mechanisms: (1) ↑ in metabolism without any variation of heat loss (n = 1), (2) ↓ heat loss without changes in metabolic heat production (n = 3), and (3) ↑ metabolic heat production associated with a ↓ heat loss (n = 5)
Golden [94]	16 M: 8 M passive immersion, 8 M exercising while immersed	10 head-out cold water immersions over 2 weeks: 2 shivering threshold immersions, 8 40 min resting cold water immersions	Shivering threshold immersion: 35–35.5°C water for 10 min, then water cooled by 1°C every 5 min Resting Immersions: 15°C, wearing only swimming trunks	Longitudinal passive observation: measurements taken throughout each individual immersion	In the static group: HR recorded over first 5 s of immersion and ventilation over the first 15s ↓ in last immersion than 1st, ↓ in initial shivering, ↑ initial thermal comfort (↓ in initial, first minute, responses to cold); ↓ metabolic response to prolonged immersion In the dynamic group: ↑ in metabolic response to cold in some subjects; ↓ VO2 during last shivering threshold immersion In both groups: ↔ Tc or Tb
Stocks [95]	7 M	90 min passive cold-water immersions daily on days 2–7 and 9–14 (total 12 immersions), Immersed to the 4th intercostal space seated	18.4°C; wearing only swimming costumes	Cold-water stress tests (CWST) on days 1, 8, 15: ~18°C 60 min seated + 30 min cycling	↓ in thermogenic response during the rest phase of the 3rd CWST beyond 20 min compared to the 1st, extending only into the first 10 min of exercise; ↔ Tes,Tsk
Lunt [102]	32 M; 16 M cold water immersion, 16 M thermoneutral water immersion	6, 5 min water head-out immersions (2x/day)	Cold (12°C) or thermoneutral (35°C)	Pre and post testing: 100 W cycling breathing normoxic (FIO2 = 0.21) and hypoxic (FIO2 = 0.12) mixtures	Post repeated cold water immersion, ↑ HRV high frequency power and ↓ adrenaline and noradrenaline during hypoxic exercise exposure; Adrenaline and noradrenaline ↓ during hypoxic exercise after cold water immersion compared to thermoneutral immersion; ↓ in number of hypoxic symptoms and symptom severity with cold water immersion group but not thermoneutral group
Tipton [103]	21 M; split into 3 groups: CON (n = 7), CORE (n = 7), SKIN (n = 7)	CORE group: 5 head-out cold water immersions where Trec was reduced by 1.18°C and Tsk decreased to 13.48°C SKIN group: 5 head-out cold water immersions for only 5 minutes, only Tsk was reduced to 13.52°C	CORE & SKIN groups: 12°C water wearing a bathing costume	Pre and post testing: 2 head-out immersions one-two weeks apart in stirred water at 12°C until rectal temperature fell to 35°C or 90 min had elapsed; wearing bathing costume	Only the deep-body cooling (CORE group) displayed a ↓ metabolic response during the post immersion until Trec ↓ by 1.18°C, with no habituation observed when cooled further; SKIN group showed habituation in the ventilatory response during the first 5 min of the post immersion but ↔ in metabolic response; Overall, ↓ in skin and deep-body temperature can habituate the metabolic response with tissue temperature specificity, cooling of only skin temperature is sufficient to lower the cold shock response but not capable of inducing habituation of the metabolic response
Brazaitis [111]	14 M	17 total sessions (14 consecutive days) of head-out cold water immersion over 20 days; for session 1–16 cold water exposure until Trec of 35.5°C or until 120 min of exposure, session 17 followed the same duration as session 1; for all sessions subjects were removed from cold immersion every 20 min for 10 min and then resumed	14°C cold water; wearing swimming shorts	Longitudinal passive (time-focused) observation; Cold water immersions 1 and 16 served as a pre and post test; immersion 17 served as an immersion 1 time matched post test	In first 6 sessions, a hypothermic acclimation (↓ metabolic heat production, VO2, shivering sensation, and Trec) was found that transitioned to hypothermic-insulative from sessions 7–16 marked by greater ↓ Tsk and Trec with ↔ in metabolic heat production; the time-matched control (session 17) demonstrated a hypothermic acclimation marked by ↓ in metabolic heat production and greater ↓ in Trec with ↔ Tsk; presence of metabolic thermogenesis ↑ only present under thermoneutral conditions; ↓ cold-stress markers, activity of the innate immune system, suppression of specific immunity, and discomfort and cold sensation; in both sessions 16 & 17 ↓ in intramuscular temperature
Gordon [125]	7 M	1 h of daily head-out circulated cold water immersion for 7 consecutive days	14°C (designed to ↓ core temperature by ~1°C daily); wearing swimming trunks	Pre and post testing: Novel skin temperature clamping (26°C) cold exposure protocol using a liquid conditioned suit passively administered for 150 min	Acclimation protocol ↓ total shivering intensity by 36% with ↔ whole body heat production, suggesting non-shivering thermogenesis from skeletal muscle can be increased substantially by as little as 7 days of cold exposure; Tes daily rate of ↓ was reduced on average by ~0.01°C/min and thermal sensation ↑ from day 1 to 7