Compared with thermoneutral showering, 4 weeks of post-training contrast heat-cold showering produced short-term favorable between-group changes in autonomic regulation and perceived recovery, but not in morning cortisol or PORH-derived microvascular reactivity, and these effects were not maintained after wash-out.
Key Findings
Results
Contrast heat-cold showering produced a favorable between-group change in resting heart rate compared to thermoneutral showering at post-intervention (T1).
Between-group difference in resting HR: Δ∆ -2.10 bpm (95% CI -2.24 to -1.96; g -0.65; p < 0.001)
Effect size was medium (Hedges' g = -0.65)
This change was not maintained at the 2-week wash-out (T2), with T2-T0 p > 0.05
Study involved 60 combat-sport athletes randomized to contrast or thermoneutral showers, with per-protocol analysis including n = 57 (≥75% compliance)
Results
Contrast heat-cold showering produced a favorable between-group change in lnRMSSD (a measure of heart rate variability) compared to thermoneutral showering at post-intervention.
Between-group difference in lnRMSSD: Δ∆ 0.123 log units (95% CI 0.108 to 0.137; g 0.74; p < 0.001)
Effect size was moderate-to-large (Hedges' g = 0.74)
Similar between-group effects were observed for RMSSD and SDNN at T1
These autonomic changes were not maintained at the 2-week wash-out (T2), with all T2-T0 Δ∆ p > 0.05
Results
Contrast heat-cold showering produced a favorable between-group change in Total Quality Recovery (TQR), a measure of perceived recovery, compared to thermoneutral showering at post-intervention.
Between-group difference in TQR: Δ∆ 0.61 points (95% CI 0.27 to 0.95; g 0.80; p < 0.001)
Effect size was large (Hedges' g = 0.80)
This perceptual change was not maintained at the 2-week wash-out (T2), with T2-T0 p > 0.05
TQR is a perceptual/subjective recovery scale used as one of four primary outcome domains
Results
Morning salivary cortisol showed no statistically clear between-group differences at either post-intervention (T1) or wash-out (T2).
All cortisol between-group comparisons yielded p > 0.05 at both T1 and T2
Cortisol was measured as morning salivary cortisol averaged over two mornings
Cortisol was one of four primary outcome domains (endocrine domain)
Primary analyses were per-protocol (≥75% compliance; n = 57), with intention-to-treat sensitivity analyses also conducted
Results
Post-occlusive reactive hyperemia (PORH)-derived microvascular reactivity outcomes showed no statistically clear between-group differences at either post-intervention (T1) or wash-out (T2).
All PORH-derived outcome between-group comparisons yielded p > 0.05 at both T1 and T2
PORH was one of four primary outcome domains (microvascular domain)
The absence of microvascular effects was found despite favorable autonomic and perceptual changes
Results
None of the favorable effects of contrast heat-cold showering observed at post-intervention were maintained after a 2-week wash-out period.
All T2-T0 between-group differences for autonomic and perceptual outcomes had p > 0.05
The wash-out period lasted 2 weeks following the 4-week intervention
The authors state that 'causal attribution to the shower intervention alone and claims of persistent physiological adaptation should be made cautiously'
This pattern suggests transient rather than durable physiological adaptation
Methods
The study design used an active thermoneutral shower comparator rather than a no-treatment control, allowing isolation of temperature-contrast effects from other showering-related factors.
Contrast shower protocol: 10 minutes alternating warm (38-40°C) and cold (13-15°C) water
60 combat-sport athletes were randomized; per-protocol sample was n = 57 with ≥75% compliance
Trial registered as ISRCTN15418049
What This Means
This research suggests that taking contrast showers — alternating between warm (38-40°C) and cold (13-15°C) water — after training for four weeks produces modest but measurable short-term improvements in how the nervous system regulates the heart and how athletes feel they are recovering, compared to taking a similar-length shower at a neutral temperature. Specifically, combat sport athletes who used contrast showers showed better heart rate variability (a marker of autonomic nervous system health) and reported feeling more recovered after the four-week program. However, these benefits disappeared within two weeks of stopping the showers, and no meaningful differences were found in stress hormone levels (cortisol) or blood flow responsiveness in small blood vessels.
The finding that benefits faded quickly after the intervention ended is important because it suggests contrast showering does not produce lasting physiological changes — athletes would need to keep doing it consistently to maintain any effects. The study also found no impact on two other expected recovery markers (cortisol and microvascular reactivity), meaning the benefits appear limited to autonomic and perceptual domains rather than representing a broad multisystem recovery effect.
This research matters because contrast showering is widely used by athletes as a recovery tool, yet rigorous comparative evidence has been limited. By using an active comparator (thermoneutral showers) rather than no treatment, this study more precisely isolates the role of temperature contrast itself. The results suggest that while contrast showers may offer some short-term benefits for heart rate variability and perceived recovery in combat sport athletes, practitioners should be cautious about claiming broad or lasting physiological adaptation from this practice alone.
Hagner-Derengowska M, Trybulski R, Kruk J, Clemente F, Olchowy C, Pilis K. (2026). Contrast Heat-Cold Versus Thermoneutral Showering in Trained Combat Sport Athletes: A Randomized Field Trial of Recovery Outcomes.. Journal of sports science & medicine. https://doi.org/10.52082/jssm.2026.675