Thomas's response to Derek's words are a one shouldered shrug and crooked smile that was still on his face when Derek's changed their route. He'd been expecting something like this, something to try and throw him off and he'd been ready.

He didn't try and match Derek's speed because he knew doing that would only blow out his lungs. That'd be a pretty terrible way to end their run. When Thomas fell behind again, he laughed though he wasn't sure if Derek would hear it. The sounds of their feet hitting dirt and Thomas's quick breathing might have muffled the sound but maybe Derek's enhanced sense had heard it anyway.

Thomas put on his own burst of speed, keeping close to Derek's heels. The last time he'd run on dirt prior to his arrival had been in the Scorch. That dirt had been hard and unforgiving. Deprived of water and nutrients, it'd been comparable to running on the hardest of stone. This dirt was soft and rich and Thomas couldn't stop himself from inhaling greedily.