The photo that accompanies this column is a less dramatic approximation of the one on page 3 of Sports Illustrated magazine’s Olympic Preview issue that showed Michael Phelps’s crawl stroke. That one was caught at the perfect instant to demonstrate for swimmers all I’ve been emphasizing in these columns.

It is plain to see here that the front crawl is not performed on the front, but consists of alternating propelled glides on both sides through the front. Like this swimmer, Phelps is riding on his left arm, which is extended into the water at a downward angle, his body knifing as narrowly as possible through a small hole in the water.

His head rests on his shoulder, creating a bow wave, behind which it is easy to take a breath without lifting his head or turning it excessively.

His right-arm recovery is achieved by lifting only his upper arm and elbow and relaxing (more than this swimmer) his lower arm and hand. Because he is on his side, the recovery can be straight up and not outside his bodyline to cause an inefficient sideward rotation. His hand will stay relaxed until it enters the water to extend to the same position on his right side that you see for his left side.

He has not yet begun to stroke with his left arm. His right arm and hand have not at this point recovered sufficiently to cause his shoulder girdle to initiate a backward motion toward his feet. He will let his shoulder muscles begin his left arm stroke, a catch-outsweep-insweep motion that, similar to his recovery, stays close to his body as it rotates from left side glide to right.

Unlike this swimmer, Phelps’s hip is at or above the water level. Because his arm and hand are angled under water, it means that he is actually swimming “downhill.”

Michael Phelps has physical gifts – long torso, long arms, big hands, big feet, great flexibility, huge lung capacity, etc. – that contribute to making him the greatest swimmer of all time. But even with these gifts, he adheres to the fundamentals of efficient swimming.

None of us can be Michael Phelps, but all of us can become efficient swimmers.

Dr. Bob Colyer of Bluffton is an actively retired college professor and coach who has recently published “Swim Better: A Guide to Greater Efficiency for Swimmers & Instructors.”