Read the passage.

The treadmill began to whir, and my heart sped up faster than the belt could go. Instead of pressing "select" on my remote control to escape into a TV show, I had just selected "Power Run." A sleek screen with a simple set of red lines showed me the terrain on which I was running. Those red lines looked like a pulse, and they got me to run farther and faster than I could ever run when I'm outside, worried about weather, cars, or other people. It may not have looked like I was going anywhere that night, but I had just broken out of a ten-year slump.
What is NOT the tone of the passage?

enthusiastic

exuberant

unimpressed

excite