Cold Water Immersion: Protocol from 55 Randomised Trials

Cold baths after exercise have been practised in professional sport for decades. Until recently it was difficult to compare different protocols directly: studies used different temperatures, durations and outcome criteria. In 2025, Wang H., Wang L. and Pan Y. (Capital University of Physical Education and Sports, Beijing) published a network meta-analysis in Frontiers in Physiology, enabling a direct comparison of six cold water immersion protocols within a single evidence network.

What happens in the body on contact with cold water?

Immersion in cold water induces vasoconstriction — narrowing of peripheral blood vessels — lowers muscle tissue temperature and slows nerve conduction. This temporarily reduces pain sensitivity and inhibits inflammatory processes around damaged muscle fibres.

At the same time, the meta-analysis by Cain T. et al. (PLOS ONE, 2025, 11 RCTs, 3177 participants) documented a brief rise in inflammatory markers immediately after the procedure and at one hour (SMD: 1.03–1.26). This reflects a normal protective response to cold stress, not a sign of harm.

DOMS: which protocol reduces pain most effectively?

In the meta-analysis by Wang et al. (55 RCTs, 1139 participants), the authors analysed three outcomes: delayed-onset muscle soreness (DOMS), jump performance and CK levels. Six protocols varied by temperature (low 5–10°C, moderate 11–15°C) and duration (short less than 10 min, moderate 10–15 min, long more than 15 min).

For reducing DOMS, the winner is moderate temperature combined with moderate duration: 11–15°C, 10–15 minutes. SMD = −1.45 (95% CI: −2.13 to −0.77), p < 0.01. This is a large effect — almost 1.5 standard deviations of reduction in subjective pain compared with passive rest.

• 42 of 55 studies reported on DOMS — a sufficiently broad sample for robust conclusions;
• the coldest (5–10°C) and longest (>15 min) protocols were inferior for pain control;
• extreme cold is not equivalent to a "better" outcome — it shifts the balance towards other effects.

Muscle damage and jump performance: when is colder water needed?

For recovery on biochemical markers and neuromuscular function, lower temperature is preferable. For CK levels (a marker of muscle fibre breakdown), first place went to the 5–10°C, 10–15 min protocol with SUCRA = 75.7% — both temperature variants significantly reduced CK, but colder water was more effective.

For restoring jump performance, the same low-temperature variant led: SMD = 0.48 (95% CI: 0.20–0.77), p = 0.01. For athletes who need to restore explosive power before the next training session or competition, the colder protocol is preferable.

Stress and wellbeing: what does the second meta-analysis show?

Cain T., Brinsley J., Bennett H. and co-authors (PLOS ONE, 2025) systematically reviewed 11 RCTs with 3177 participants, focusing on effects on general health and wellbeing. Key findings:

• stress levels were significantly reduced 12 hours after the procedure: SMD = −1.00 (p < 0.01);
• no immediate reduction in stress was detected;
• no significant effect on mood was found in the available data (one RCT);
• one study recorded a 29% reduction in sick days among cold shower practitioners — data are from a single study.

Three caveats worth keeping in mind

First: the brief inflammatory spike after immersion (SMD of inflammatory markers 1.03–1.26 per Cain et al.) is a response to acute stress, not long-term harm. The anti-inflammatory effect of cold appears later.

Second: some research points to possible attenuation of anabolic adaptation signals with regular post-workout immersions. This area is still being investigated; when hypertrophy is the priority it is sensible to schedule sessions on non-training days or several hours after training.

Third: the protocols across studies varied considerably in methodology, so individual responses may differ. The response to cold also depends on habituation: regular practice changes both the physiological and psychological response.