Your ice bath keeps cooling you long after you climb out

Cold-water immersion is one of the most popular recovery rituals in sport, yet protocols vary wildly: some athletes sit in near-freezing water for a few minutes, others use milder water for longer, some dip in and out. If the point of the practice is to cool the body, then it matters whether those choices actually change how much the core cools, and for how long. Core temperature is the physiological variable most of these protocols are implicitly trying to move, so mapping how protocol details shape it is the first step towards informed prescription rather than folklore.

The researchers pooled data from 157 subjects who had taken part in previous post-exercise cold-water immersion trials run in their own laboratories. The protocols across those trials varied in water temperature, immersion duration, immersion depth and mode, meaning continuous soaking versus intermittent dunking. Core temperature was analysed as a double difference: the change in core temperature during the immersion condition minus the corresponding change in the control condition. Statistical models were run separately across two time windows, the immersion period itself and the period after the intervention.

Protocol details mattered. Intermittent immersion produced a mean core temperature drop 0.25°C greater than continuous immersion during the immersion period. Water temperature had its own effect: each 1°C reduction in water temperature deepened the core temperature drop by 0.03°C. Duration counted too, with every additional minute of immersion adding a 0.02°C decrease. Perhaps most strikingly, the peak difference in core temperature between immersion and control did not occur in the water at all: it arrived at 60 minutes after the intervention, meaning the body kept drifting cooler well after exit.

This analysis shifts cold-water immersion from a yes-or-no question to a dosing question, showing that mode, temperature and duration each independently shape the physiological result. It does not, however, say anything about whether more core cooling means better recovery, less soreness or improved next-day performance; those outcomes sit outside this dataset. The data also come from one group of laboratories' own trials rather than a sweep of the whole field, so the numbers are best read as careful estimates rather than final values. The authors themselves frame the work as a guide for choosing protocol factors deliberately.

If ice baths are part of your routine, this is a reason to think the details of your setup are not interchangeable: a colder, longer or intermittent protocol cools your core more than a milder, shorter, continuous one. It is also a reason to appreciate that the cooling is not over when you towel off, since the largest difference from skipping the plunge arrived an hour later. What this evidence cannot tell you is whether deeper cooling improves your recovery, so it informs how you cool, not whether you should.