" The most successful football linebackers are massive because their job is either to be immovable (offensive linemen) or to move the immovable (defensive linemen). Tennis players typically have average builds because their sport requires a combination of qualities—quickness, power, leverage, balance, and stamina—that favors no extremes of size or shape. Endurance sports, of course, tend to favor two related characteristics: low body weight and lean body composition (or a low body-fat level). This is the case because endurance racing demands the ability to move economically so that a high work rate (or speed) can be sustained for a long time and a low body weight and lean body composition contribute to movement efficiency. "

― Matt Fitzgerald , Racing Weight: How to Get Lean for Peak Performance