It goes back a little over 50 years to what became a bible of our sport – Dr. James “Doc” Counsilman’s “The Science of Swimming.” On page 2, my mentor writes that, to be more efficient, “a swimmer … must do one of the following: (1) decrease resistance, (2) increase propulsion, or (3) use a combination of these two.”
Reducing resistance for the long-axis strokes (front or back crawl efficiency) requires the swimmer to be as long and narrow as possible, or as fish-like as possible. The only fish that is flat on the water’s surface is a dead fish. Therefore, front and back crawl are not swum ON the front or back.
They are instead swum by alternating sides THROUGH the front or back, using a glide position that extends the lead arm forward below the surface while the trailing arm’s hand touches the thigh below the hip.
Breaststroke and butterfly by definition use both arms simultaneously, so their glide positions, even though level on the front, require full extension of legs and arms to reduce resistance.
Increasing propulsion requires using both “drag” and “lift” forces. Drag force follows Newton’s Third Law of Motion by exerting pressure backwards on the water so that the body moves equally and opposite, thus forward.
Lift force works like an airplane wing as the hand-arm lever moves through the water, creating greater pressure on the underneath side and lowering pressure on the upper side. Thus the “wing,” and the body to which it is attached, moves from an area of greater pressure to an area of lesser pressure according to Bernoulli’s Principle of fluid dynamics. If the greater pressure is toward the rear, resulting “lift” moves the body forward.
Drag and lift forces vary as hand and arm angles vary. Thus there is no constant proportion of drag and lift from stroke to stroke, nor throughout any given stroke. The best I can say is that both are continuously at work, efficiently or not.
Swimmers who minimize resistance and/or who maximize the effect of the two propulsive forces can be said to be more efficient than others. That is my goal in the teaching of aquatic locomotion.
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. firstname.lastname@example.org