Pre-exercise cold water immersion boosted endurance performance in the heat; ice ingestion did not

Researchers pooled 22 crossover studies to compare two precooling strategies—cold water immersion and ice slurry or crushed ice ingestion—on endurance performance and body-temperature regulation during exercise in warm conditions. Cold water immersion was associated with a moderate improvement in endurance outcomes, while ice ingestion showed no clear performance benefit.

What the study found

Cold water immersion before exercise was associated with a moderate positive effect on endurance performance measures—such as time-to-exhaustion and time trials—with a weighted effect size suggesting a meaningful but not large advantage over doing nothing. Ice ingestion, by contrast, produced an effect size whose confidence interval crossed zero, meaning the data did not clearly distinguish it from a passive control.

On the physiological side, cold water immersion was linked to lower peak core temperature, reduced whole-body sweat response, and lower thermal sensation during exercise, alongside a greater rise in skin temperature as exercise progressed. Heart rate and perceived exertion were not meaningfully different from control conditions under either strategy.

Ice ingestion did produce greater rises in both core and skin temperature during exercise compared with control—an unexpected direction suggesting the body may respond differently to internal versus external cooling—yet these changes did not translate into detectable performance gains or shifts in sweat rate, heart rate, or perceived exertion.

The authors concluded that, when viewed through both a performance and a thermoregulatory lens, cold water immersion appears to be the more effective precooling approach ahead of exercise in the heat, though they frame this as a probabilistic inference rather than a definitive causal claim.

Limits worth knowing

The meta-analysis drew on 22 studies, but the individual trials varied in participant characteristics, exercise protocols, ambient conditions, and immersion parameters, introducing heterogeneity that pooled effect sizes can only partially account for. All studies required exercise in ambient temperatures of 26 °C or above, so findings may not generalize to cooler environments. The review focused on acute performance and physiological responses; longer-term or repeated-exposure effects were not examined. Funding sources for the included primary studies were not uniformly reported, and the review itself does not disclose industry support. The analysis was restricted to crossover designs with passive controls, excluding comparisons with other active recovery or cooling strategies.

About this entry. The Heartwood Review summarizes published, peer-reviewed research in its own words and links to the original source. It is not medical advice; consult a physician before beginning or changing any thermal or recovery practice. Findings summarized here describe the study cited, not any product sold by Teak & Marble Atelier. Corrections.