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Hot Water Immersion and Muscle Regeneration: Evidence from a 2025 RCT

A 2025 RCT compared hot, cold, and thermoneutral water immersion after acute muscle damage: hot water reduced damage markers and activated heat shock proteins — cold water provided none of these benefits. A breakdown of the protocol, numbers, and limitations.

5 min readRecovery10/13/2026
Quick Answer

Hot water immersion at 42°C for 60 minutes daily over 10 days reduced creatine kinase (CK) by ~2,163 U/L and myoglobin by ~897 µg/L compared to thermoneutral water, significantly increased HSP27 and HSP70 expression, and reduced perceived pain (Dablainville et al., Journal of Physiology, 2025; n=34 males). Cold water immersion showed no comparable benefits.

What Is Hot Water Immersion and How Does It Act on Muscles?

Immersion in hot water (40–43°C) is a thermal recovery method in which the rise in tissue temperature triggers the expression of heat shock proteins (HSP). HSP act as molecular chaperones: they prevent aggregation of damaged proteins, accelerate clearance of cellular debris, and participate in regulating the inflammatory response. The logic is the opposite of a cold-water strategy, which relies on vasoconstriction and suppression of inflammation.

How Was the Dablainville et al. (2025) Trial Designed?

Dablainville V. and colleagues (Journal of Physiology, 2025) divided 34 healthy males (mean age 33 ± 3.5 years) into three parallel groups:

  • Hot water immersion (HWI): 42°C, 60 minutes, daily for 10 days.
  • Thermoneutral water immersion (TWI): ~35°C, same protocol.
  • Cold water immersion (CWI): ~10–15°C, same protocol.

One hour after muscle damage (electrically stimulated eccentric contractions — a standard model of acute muscle damage), participants began their daily sessions. Blood samples and muscle biopsies were taken every other day throughout the observation period.

What Did the Muscle Damage Markers Show?

In the hot water immersion group, creatine kinase (CK) levels were approximately 2,163 U/L lower than in the thermoneutral water group (p ≤ 0.012). Myoglobin concentration was lower by 897 µg/L (p < 0.001). Cold water immersion showed no comparable benefits on these markers.

Perceived muscle pain in the HWI group was significantly lower than in the TWI group (p = 0.035). No statistically significant differences in the recovery of strength measures were found between the three groups.

In the hot water immersion group, HSP27 and HSP70 increased by day 11 — in the cold water immersion group, their expression was suppressed. Two opposite responses to two opposite temperature stimuli.

How Do Heat Shock Proteins and Inflammatory Markers Behave?

HSP27 and HSP70 increased significantly in the HWI group by day 11 (p < 0.038). No such increase was observed in the TWI or CWI groups; in the cold water immersion group, HSP expression appeared to be suppressed.

NF-κB (nuclear factor kappa-B — a key regulator of the inflammatory signal) remained stable in the HWI group, whereas in the TWI and CWI groups its expression increased. Interleukin-10 (IL-10, an anti-inflammatory cytokine) was significantly elevated only in the HWI group on day 11 (p = 0.014). Together, these findings suggest that hot water immersion limited the pro-inflammatory response via the NF-κB pathway while simultaneously boosting the anti-inflammatory response via IL-10.

What Does the 2024 Network Meta-Analysis Show?

Chen R. et al. (BMC Musculoskeletal Disorders, 2024) conducted a network meta-analysis of 57 trials in healthy participants following exercise-induced muscle damage. For the CK marker, contrast hydrotherapy (alternating hot and cold water) showed the best result. For reducing DOMS and restoring jump performance, cryotherapy led the field. Isolated hot water immersion ranked below contrast hydrotherapy as a CK-reduction strategy according to this meta-analysis.

What Are the Limitations of These Data?

The Dablainville et al. trial included only males. A randomized trial in women (PLoS ONE, 2025) showed no acceleration of recovery with either HWI or CWI compared to control over a 72-hour observation period. The sample size of Dablainville et al. (n=34) is small. The damage model used electrically stimulated eccentric contractions rather than standard training, which limits the transfer of results to real-world training practice.

What This Means in Practice
  • During rehabilitation from injury with muscle damage, hot water immersion (42°C, 30–60 min) is a well-supported choice based on 2025 data: reduced CK and myoglobin, HSP activation, and decreased perceived pain.
  • Do not confuse goals: for reducing acute soreness (DOMS) in the first 48–72 hours, the 2024 network meta-analysis points to cryotherapy; hot water immersion works better on regeneration markers with longer-term use.
  • Cold water suppresses HSP expression — if the recovery goal includes activating heat shock proteins, cold water immersion is directly counterproductive to that aim.
  • The picture differs in women: 2025 data did not reproduce benefits from either hot or cold immersion in a female sample — apply with an adjustment for sex.
  • For reducing CK after exercise-induced damage, contrast hydrotherapy outperforms isolated HWI according to the 2024 network meta-analysis.

Frequently Asked Questions

What are heat shock proteins and why do they matter for muscle recovery?
Heat shock proteins (HSP27, HSP70) are molecular chaperones synthesized by cells in response to thermal stress. They protect proteins from denaturation, accelerate repair of damaged cellular structures, and participate in regulating the inflammatory response. In the RCT by Dablainville et al. (Journal of Physiology, 2025), their expression increased significantly after a 10-day course of hot water immersion at 42°C (p<0.038).
Hot or cold water: which is better for muscle recovery after exercise?
It depends on the goal. For reducing muscle damage markers (CK, myoglobin) and perceived pain, Dablainville et al. (Journal of Physiology, 2025) point to an advantage for hot water immersion. For reducing DOMS and neuromuscular recovery in the first 48–72 hours, the network meta-analysis by Chen et al. (BMC Musculoskeletal Disorders, 2024) favors cryotherapy and contrast hydrotherapy.
At what water temperature are heat shock proteins activated?
The Dablainville et al. (2025) trial used a temperature of 42°C for 60 minutes daily over 10 days. At this temperature, thermal stress is achieved in muscle cells without risk of skin burns. Lower temperatures (38–40°C) activate HSP to a lesser degree, though the exact threshold requires further investigation.
Do these findings apply to recovery from regular strength training?
Directly — with caveats. The Dablainville et al. RCT modeled acute muscle damage using electrically stimulated eccentric contractions, not standard training. For recovery from strength training as such, the evidence is limited: the network meta-analysis by Chen et al. (2024) covered exercise-induced muscle damage protocols, and the picture there is mixed.

Sources

  1. Dablainville V. et al. «Muscle regeneration is improved by hot water immersion but unchanged by cold following a simulated musculoskeletal injury in humans». The Journal of Physiology. 2025. pmc.ncbi.nlm.nih.gov/articles/PMC12666504
  2. Chen R., Ma X., Ma X., Cui C. «The effects of hydrotherapy and cryotherapy on recovery from acute post-exercise induced muscle damage — a network meta-analysis». BMC Musculoskeletal Disorders. 2024. bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/s12891-024-07315-2
  3. Moser O. et al. «No acceleration of recovery from exercise-induced muscle damage after cold or hot water immersion in women: a randomised controlled trial». PLoS ONE. 2025. journals.plos.org/plosone/article?id=10.1371/journal.pone.0322416
This material is for educational purposes only and does not constitute medical advice.

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