My knee: It’s hurting. But I’ve only got 15 minutes left to go — so I keep going.

This is a stupid thing to do. I know, because by Wednesday there’s pain boiling through the side of my knee when I stand up.

I was doing my cardio workout on the eliptical machine, having fun, pumping a heavy dose of metal through my iPod and barely winded when I hit the 30-minute mark.

So I thought… I could go another 30. Mind you, I started out doing 20 minutes at level three, six weeks ago. Last night, I was on level 5, and going for an hour.

So at 45 minutes, I get this pain in the side of my knee.

And I think “I’ll tough it out for 15 more minutes.” This is the stuff tough guys are made of, right? Be a man — walk it off.

Well, it slowly got worse until, by the end, I was pushing more with my arms and my left leg to keep the load off of the painful joint.

This is one of the main reasons people quit working out: They over-extend themselves and get hurt.

Today, there’s pain boiling through the side of my knee when I stand up from a seated position. It’s not cool. And the hour I bought by overextending myself might shake out to hours of missed cardio time if this turns out to be serious.

The moral of the story: Don’t overdo it.

Bryan