Quadriceps - the large muscle in front of the thigh, the strength of which helps determine a cyclist's ability to pedal with power.

Quick releases -The older ones, from Shimano, were heavy. So lots of companies - especially Ringle - started making expensive replacement QRs. Some worked. Some didn't. Then Shimano did what it does best: it improved it's stuff so that it was better (and cheaper) than the aftermarket competitors. And another class of off-road entrepreneurs were forced to move on.

Quiet -All alone, playing hooky from work, middle of the day, your favorite trail. The incredible stillness, all around you. Just gliding along the rolling terrain. C'mon, call in sick and try it. You'll be happy for weeks.