A couple of years ago, I wrote a column about elbows being one key to increased propulsion and swimming more efficiently. This column discusses a key to decreasing resistance, the other aspect of efficient swimming.

One might consider this key to be the head. If the head is held above the water in any stroke, the whole surface of the upper body is exposed against the water, greatly increasing resistance.

However, it’s the reaction to the head lift that counts. Raising the head lowers the hips, the real key to keeping resistance to a minimum. An efficient swimmer’s hips stay close to the surface.

Many years ago, for a graduate school paper, I plotted the paths for shoulders, knees, hips and center of gravity (a real challenge) for an Olympic champion butterflyer through a full stroke. I found that the flattest path was for the hips. It is true for the other strokes, too, even though they lack such an up-and-down body motion.

The long-axis strokes (front crawl, back crawl, sidestroke) achieve this in a glide position with the head in the water along with an extended leading arm, bringing the legs up toward the surface. For the short-axis strokes (breaststroke, butterfly, elementary backstroke), the two arms and the head in the water help lift the legs to glide on the surface. In both situations, the hips act as the fulcrum for the “seesaw” of the extended body.

How does a swimmer act on this knowledge to make his/her strokes more efficient? For the upper body, it is vital to keep the head in the water. Turn the head (with the body) only enough to breathe in the trough created by the head, or lift the head only enough to drag the chin through the water.

Counterbalance this with the lower body’s kicks that raise the hips and keep them on the water surface. The abdominal muscles need to be involved for all kicks. These actions are not as hard to do as it may seem.

Bottom line: Use your hips to keep a long and slim body line through the water and thus reduce resistance. Simultaneously, use your elbows to apply forces that move the body past an anchored hand-arm lever. If you do, you will become an effective, relaxed, and thus highly efficient swimmer.

Dr. Bob Colyer of Bluffton is an actively retired college professor, coach and author of “Swim Better: A Guide to Greater Efficiency for Swimmers & Instructors,” directed primarily to non-competitors. bobcolyer@yahoo.com