Today is Cinco de Mayo, and if you're planning on celebrating with a few margaritas or Mexican beers, you may want to skip that run tomorrow. Why? Well, drinking alcohol doesn't mix with running because alcohol has a dehydrating effect. So if you're feeling hungover at the start of your run, you're actually starting your run dehydrated, which is never a good thing. If you really want to drink tonight and run tomorrow, try to limit yourself to one alcoholic beverage and be sure to drink plenty of water.