In terms of athletic performance, often athletes work specific muscles or muscle groups to improve ability at the margin(e.g. a higher jump or more powerful kic

In terms of athletic performance, often athletes work specific muscles or muscle groups to improve ability at the margin(e.g. a higher jump or more powerful kick) or to lower the risk of injury from sudden, unpredictable movements(wrestlers have powerful necks in part because neck injuries are career-enders). A general, untargeted approach like "carry a young calf around the stadium" (the approach claimed to be used by ancient wrestler Milo of Croton) also builds strength, but more in a sense of overall athleticism, which is generally good for health but doesn't necessarily optimize towards a specific activity: e.g. the possibility of becoming "too big" presents itself wherever you're relying on a blend of speed, strength, and stamina. Strongmen competitors are very strong, but they don't have as much stamina or speed as people who trained to be strong at a lower weight. For many people, it's aesthetically driven: bodybuilding is a form of beauty contest where a certain kind of muscle development and leanness is considered ideal, depending on the specific contest you're entering. And so you train and diet accordingly: gaining mass in areas that need to be brought up, trying to even out two sides where their size differs, dieting down to show more of the anatomy. Even if you aren't aiming to enter shows, many people will use these parameters as an aesthetic target. If you're in it for general health, the distinctions are interesting trivia, but you're basically served by doing exercises that are known to train all parts of the body. Combat sports offer a good model for this kind of training since they demand an overall balance of athleticism, and to eliminate exploitable weaknesses.