Is working out supposed to make you sleepy?

Is working out supposed to make you sleepy? It feels kinda counterintuitive, right? You're all energized and sweaty, then BAM, ready for bed? Well, it actually makes a lot of sense. Working out does a number on your body temperature – heats you up like crazy. But then, like a half-hour to an hour and a half later… it starts to cool down. And that, my friend, is the magic sleep window. It's like your body's natural cool-down is a signal for bedtime.

I remember training for a half-marathon a few years back. I'd be out pounding the pavement, feeling like I could conquer the world. But later that evening? Out cold. Like, seriously, lights out before 9 pm sometimes! And I wasn't even trying to go to bed early. It just happened. So, yeah, the whole body temperature thing? I definitely buy it.