Had to add one more clip from a TI article:
Body rotation in swimming generates propulsion just as it does in baseball, golf, or tennis (or in throwing a javelin or a punch): A biomechanical chain reaction occurs, in which the legs propel the hips, which power the torso, which drives the last link in the kinetic chain--the shoulders and arms. The most powerful movements don't start and stop in any one joint; when we employ precise body mechanics, power ripples through our bodies like it does through a cracked whip until it finally arrives at the point where it's released.
But there is one key difference in how swimmers use the kinetic chain compared to land-based athletes. On land, the chain reaction starts with twisting the body away from the direction of the swing while the legs are anchored to the ground, an action known as elastic loading, similar to a rubber band being stretched before firing. The hip **** acts like the handle of a whip, throwing the energy upward through torso, shoulders, and arms with increasing speed and power. Since swimmers cannot anchor their feet to the ground, the hips cannot act as a whip handle, making it essential that you focus on moving the entire torso.
When we are swimming with maximum effectiveness, it is torso rotation that thrusts the recovering hand forward into the water at the same time that it drives the propelling hand back. We increase stroking power not by lifting weights, but by shifting from passive body roll to dynamic body rotation, pressing into service the stronger muscles of the torso that ?feed? power to the arms.
The kinetic chain most often breaks down in swimmers--even those who are balanced and roll passively when swimming slowly--when they attempt to swim faster. Because the instinct to seek power and set stroke rhythms in the arms is so strong, 99% of all swimmers churn the arms faster and harder when they want to swim faster. But a key principle of all rhythmic movements is that they should always start in the core, not in the extremities. Your arms have so much less mass than your torso that it's easy for them to get ahead of your core body rhythms. Once they do, it?s like disconnecting a boat?s propeller from its engine.
The best way to learn to swim with your body, instead of with your arms and legs, is to combine stroke drills and super-slow swimming.
