C20 Why? What is wrong?

IRA'S POV

I didn't expect it to hurt so bad.

Dexter stopped in his tracks as soon as I stopped, struggling to catch my breath.

My legs felt like they were on fire, and my joints couldn't bear to carry my body any longer.

I didn't realize I was so out of shape.

"We are barely around the first lap," Dexter said, stopping a few meters ahead of me