Four basic principles of physics governing efficient swimming are: buoyancy, gravity, drag force (resistance) and propulsion.
Buoyancy is the ability to stay near the top of the water; our lungs are air-filled and keep our torso afloat. Our legs don’t float so well, and gravity pulls them downwards, which is why we kick and press downwards on our chest as we swim—to maintain a level body position.
Water creates drag force. You can push yourself off of the pool wall, but eventually (and sadly, way too soon) you will stop moving. To keep moving, you apply propulsion with your arms and legs. That’s swimming!
Efficient swimmers work to master these four elements by maintaining a good body position with their head, hips and feet on the same level parallel to the surface of the water. Any deviance for a level position accentuates drag. In addition to maintaining good body position, efficient swimmers work to minimize the drag force and maximize propulsion.
That’s why in Week 2 of the Swim Faster program, we focus on streamlining and rotation. When you watch a pool competition, you’ll notice that good swimmers assume a tight streamline as they push off from the wall. The fastest point of any lap is the push-off phase, and the tighter the streamline the more you can minimize drag to take advantage of your speed.
Maintaining a streamlined attitude as you propel yourself down the lane is critical. Coaches and swimmers describe a swimmer’s “shadow,” which is the amount of your body exposed to the water. Imagine yourself swimming through a narrow window. The window is your shadow, and the smaller the shadow, the less drag force to slow you down.
Maintaining a smaller shadow is why I focus on the catch phase of the stroke early in my program. By entering the water cleanly--fingertips below wrist, wrist below elbow—you set up an efficient catch. As you extend your hand into the catch, imagine being as streamline as possible from your fingertips to your toes, rotated about 30 degree with one straight line from hand to foot. This minimizes your shadow while your other hand propels you forward.
Once you’ve established this position—which I describe as anchoring the stroke--you’re at the point when we start to catch water and shoot down the lane. Because you are rotated to the stroke side, your arms are set up to use your large back muscles for propulsion. Not only is good rotation important for power, but it also mitigates shoulder injuries.