Without muscles we would not be able to keep ourselves upright, and moving would be impossible. Men are genetically endowed with more muscle tissue than women, and for this simple reason a man and a woman training with the same intensity will never be equally strong or fast. But how come that is it genetically set whether a person (man or woman) is physically talented to be either a sprinter or a marathon runner? Either a judoka or a long distance swimmer? A discus thrower or a cross-country skier? Why do bodybuilders appear strong as a horse while your average weightlifter, who looks like he spends too much time observing the interior design of MacDonalds, can easily lift three times the weight a bodybuilder can.? And why do bodybuilders suck at riding the Tour de France?.
To understand how muscles and various training principles work it is necessary to look at muscles from a physiological point of view. Skeleton muscles (which are the kinds of muscles discussed here) are the muscle covering the skeleton. Each muscle is attached to bone by two tendons. Watching Robbie Williams" video for "I don't wanna rock, DJ", were Robbie, after having taken of all his clothes starts to undo himself of his muscles, we get a good impression of how all these muscles overlap each other. These muscles are able to contract at the moment the brain sends them a signal through the nerves, causing motion. Some of these signals are given unconsciously, such as the blinking of the eyes. Other contractions are carefully controlled, such as the carrying of a tray full of glasses, or the picking up of extremely fragile objects. Most contractions, however, are done consciously, but without really noticing it; no one is aware of the work the biceps, triceps, deltoids, and trapezium do to bring a piece of food to our mouths. Only when you overload your muscles (either willingly because you go to a fitness-centre and work out, or unwillingly because unexpectedly you have to carry more groceries than normal) you become aware of the frequency with which these muscles contract in daily life; they hurt and peeling your evening taters becomes an agonising experience!.
