The first run is always a bad idea. After my first 5K in three years, my legs hurt for three days. When your thighs and calves are sore, the temptation is to go lightly on each step. “No pressure. Let’s not upset these delicate little walking sticks right now.”
Ironically, the more careful you are to move as little as possible, the longer your muscles will hurt. It’s as if you’re reaffirming their right to be upset. Meanwhile, something interesting happens when you fully extend your legs, stretching them through the discomfort: Behind the pain, you’ll find power, even relief. The muscles settle into their fully engaged position, and while there is tension, there also is strength.
Repeat the process a few times, and you’re re-educating your muscles. Instead of handling them with kid gloves, you’re showing them: “Look! You can do this. It’s not that hard.” Soon enough, the soreness subsides, and you’re back on the treadmill.
Pain only doubles when we shy away from it. Lean into it, however, and it’ll quickly be cut in half. Find the power behind the pain.