Interesting concept about exercise non-responders.

Skimming through a few different articles, it appears as if people do respond to exercise, but perhaps in different ways.

See this short summary.
The Truth About Exercise Part 2- Are you a Non Responder to Fitness Training?

For me in school, I could do find with 100 yard dashes... but when it came to running a mile, I was always at about a 6 minute pace (perhaps a bit slower since then). I think what would happen is that at some point I would just drop to my normal plodding pace... and get through the exercise.

On the bike, I can hit 16 or 17 MPH... for up to an hour or so. But it is so easy to drop down to a simple plodding pace of 10 - 13 MPH, which I enjoy, perhaps more than pushing myself to 100% max and 100% burnout. Exercise doesn't wake me up, and I can nap or sleep soundly after hard riding. In the past, running would just knock me out.

I'm also a "masher". I read about people hitting 90 or 100 RPM. That just isn't me. I don't have a cadence meter, but on a recent ride, I tried to estimate the cadence by counting right strokes and watching the clock, which generally came in around 30 to 50 RPM. It may be speeding up at times, but I'm comfortable with the slower cadences.