Bill Hartman 40:06–42:00
All right. Four guys step away from the car. Six guys are now trying to hold the Jeep up, but they're failing. They're still pushing up. The Jeep is slowly going down towards the ground. The four guys jump back in. Everybody lifts the car up. Four more guys jump out, still six guys trying to hold the car up, failing miserably, but it's going down slowly because they're still pushing up. You get it? So that's what lifting weights is. I have to increase the number of motor units to lift a weight because I have to go in that direction against gravity and move away from the ground. As I lower a weight, I need to actively control the velocity of the weight. I need just enough motor units to allow me to move in the other direction downward, but the other one's got to stop. Because if I maximize the number of motor units, I can stop that weight from moving; it wouldn't move. This is the fault with the terminology. Do you understand now why I say concentric orientation, eccentric orientation? Because eccentric means away from midline. That's the definition. It means away from midline. Contraction means to make smaller. Eccentric contraction doesn't make a whole lot of sense to me. But if you tell me that a muscle is positioned eccentrically, I know what it's doing. If you tell me that a muscle is positioned concentrically, I know what it's doing. Do you see the difference?
motor unit recruitmentconcentric vs. eccentric movementmuscle terminologyweightlifting mechanicsgravity resistance