Triathlons have the swim leg first.

But what about someone who wants to relax and cool down in the water after a run? It is known that running (or any exercise really) raises body temperature a bit. It is (is it?) also known that sudden body temperature fluctuations are not a good thing.

So is there a real problem in jumping into the water while the body is still warm from the running - w.r.t body temperature regulation? How long of break is advisable before getting in the water after running?

Let us assume the water temperature is between a comfy 25-30 celsius. Although it would be appreciated if answers covered a broader range of water temperatures.

  • It probably depends on the temperature of the water, doesn't it?
    – El Guapo
    Commented Aug 30, 2019 at 16:27
  • lol yeah... just updated the q.
    – ahron
    Commented Aug 30, 2019 at 16:28
  • 2
    I remember riding my bike to the pool as a kid on hot summer days and it feeling really really good jumping in the cold (~20C) water when I got there. Turns out your body is pretty good at figuring things out.
    – Jon Custer
    Commented Sep 4, 2019 at 17:21
  • 1
    water temperature between 25 - 30°C is definitely not comfortable for me - I like to get to water below 18°C after running in a hot day and it's a great way to recover. Commented Jul 14, 2020 at 2:01

1 Answer 1


Having gone in thermal shock I can tell that is not fun, it's really painful.

But the body can adapt, it happened to me the first time I started swimming in the winter, but then I got used to it.

However don't worry, the temperature difference must be really high to suffer a thermic shock.

Like swimming in ice high...

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