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Why do runners get night sweats?

If you're waking up in the middle of the night drenched in sweat, your new training program could be the reason

With the virtual race calendar filling up (and a few hopefully in-person events on the schedule) you may have started to increase your mileage in preparation for your next big race. As your volume and intensity have been going up, you might have noticed a weird side-effect: night sweats. While night sweats are a fairly common issue that runners deal with, we often don’t talk about them because we tend to chalk them up to something else (like menopause, our room being too warm, etc.) rather than our running. If you are consistently waking up in the middle of the night because you’re overheating, it’s time to look at your training as the possible culprit.

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While there can be underlying medical reasons why someone is routinely waking up drenched in sweat in the middle of the night, if it coincides with an increase in your running volume, this change in training is likely the reason. Night sweats associated with changes in fitness aren’t typically cause for concern, but they can be very uncomfortable and can interrupt the precious sleep you need for recovery.

There are a number of reasons why your increase in training is giving you night sweats, including changes in your metabolism. Normally, your body temperature drops slightly right before you go to bed to help promote sleep. High-intensity physical activity can speed up your metabolism, which can raise your body temperature before you go to sleep, so you eventually wake up sweating. If you do most of your training later in the evening, you may also be more likely to have night sweats, because you are raising your body temperature before hitting the hay. Another possibility is that your thyroid is releasing more hormones to help fuel your increase in activity, and night sweats are a side-effect.

Night sweats can also be a sign that you are either overtraining and/or underfuelling, both of which can affect your athletic performance and your overall health. If you aren’t taking in enough calories and nutrition to support your increase in training, your blood sugar could drop and you could experience hypoglycemia, which can result in sweating at night.

How can you prevent night sweats?

If you’ve started having night sweats, it doesn’t mean you have to give up training, as long as other symptoms of overtraining (like injuries, illness, or mood changes) aren’t also present. If you’ve recently increased your training volume, it is likely that your body just needs time to adapt to the heavier load, at which point your night sweats will likely subside. In the meantime, there are a few things you can do so they’re less of a problem.

Change your sleepwear: you may want to switch to something made of a moisture-wicking material for your sleepwear, sheets, blankets and pillows. There is bedding available designed specifically for people who struggle with night sweats, and while they won’t necessarily stop them from happening, they can make you more comfortable in the process.

Run (and eat) earlier: we hate to break it to all the night runners out there, but if you tend to run late in the evening, and subsequently eat late as well, you may have to run earlier in the day to avoid night sweats. If that’s not possible, avoid eating high-glycemic carbs (like white rice, white pasta, or potatoes) late in the evening, which can spike your blood sugar post-run and cause you to wake up in a sweat.

Try a magnesium supplement: studies have shown that a magnesium supplement is effective at reducing hot flashes for women experiencing menopause, and it can help reduce night sweats in runners, too. Magnesium comes with other benefits as well, such as helping to regulate muscle and nerve function (goodbye, muscle cramps!) and improving your sleep. If supplements aren’t your thing, there are plenty of food sources of magnesium, including pumpkin seeds, beet greens, cashews, dried prunes, white beans, avocados, almonds, chickpeas, edamame and dark chocolate. If you choose to take a supplement, talk to your doctor first.

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