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I've had a couple running events recently that have been pushing my endurance (a competitive half marathon, and running 20+ trail miles for a fun-run). The night following these events I've woken with night sweats--sweating profusely in my sleep (yes, it's definately sweat).

Internet searches turn up different mentions of it and supposed explanations. I'm curious if there's any objective information about whether it's a common side-effect of hard training, or if it's indicative of either going too hard or doing something incorrect (e.g. some claim it's a side-effect of taking in too much salt).

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Do you mean the night before, or after? – Dave Newton Nov 12 '12 at 20:36
Hi Dave, it's been the night after the event. So run 20 miles, go to bed, wake up drenched in sweat. – STW Nov 12 '12 at 20:40
Huh; never experienced anything like that. Interesting. – Dave Newton Nov 12 '12 at 20:41 might point in the direction of an answer – FredrikD Nov 13 '12 at 12:35
up vote 3 down vote accepted

Night sweats can be related to an increase in exercise intensity due to the affect of exercise on the endocrine glands and hormone secreations. In general, excessive sweating at night is caused by hormones. That is why menopausal women are prone to night sweats.

However, there are also several other causes, including medical or medication causes so night sweats may warrant a medical checkup in some cases.

If you want objective information regarding the affect of increasing exercise intensity on the thyroid, see Neuroendocrinology Letters: Exercise Intensity and Its Effects on Thyroid Hormones referenced in this Livestrong article: Increased Exercise and Night Sweats

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I train for cycling time trials, ranging from 10 mile sprints to 12 hr endurance races. I train on Heart rate and power meters, so I know accurately when I've upped my endurance/fitness. I find if I have a training session, whether that be Turbo or out on the road and I've exceeded a burn of 3000 cals then that following night (without fail) I will suffer with drenching night sweats, to the point I Have to to have a bath towel under the sheet to aid in not ruining my mattress.

I've had blood tests to check for anything sinister and all came back clear, It's the increase in training that causes my drenching night sweats. The second night the night sweats seem to be halved, then the following night is usually all clear until I push my training regime once again. Hope this helps.

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