Paddle vs. Propeller     Stu Kahn, SWIMMER, April 2013

Curious minds have long pursued the best methods of swimming faster. The debate began in earnest in the late 60's, when legendary coach James "Doc" Counsilman first advanced the idea of Newton's third law of motion (to every action there is an equal and opposite reaction). A few years later, benefitting from the novel use of underwater photography, Counsilman proposed that sculling actions (lift) were the primary sources of propulsion.  This is known as the "Bernoulli theorem," which is the same theorem that explains lift in an airplane wing.

In the mid 70's, excercise physiologist and coach Ernest Maglischo took those ideas and, through his investigations and publications, led the science of swimming to its next level. After continued studies, Maglischo revisited his theories of dominant sculling contributions and reemphasized the principles of drag propulsion. That new information brings the discussion full circle, back to 50 years ago, with a renewed emphasis on straighter pull paths versus curved.

In June 2012, Rajat Mittal, a professor of mechanical engineering at Johns Hopkins University, and colleagues used computational fluid dynamics to analyze the propulsive forces of the freestyle stroke and what they termed the S-pull (propeller) and the deep-catch pull (paddle). The quantifiable aspect of their investigation looked into the relevant contributions of lift and drag forces.

[See Dr. Mittal's article on Paddle vs. Propeller]

Their research revealed that lift forces provide a dominant contribution to thrust for all the arm-pull styles examined. However, contrary to accepted notions in swimming, pronounced sculling (lateral motion) not only does not increase the contribution of lift forces on the hand to overall thrust, it decreases the contribution of drag forces to thrust. Consequently, pronounced sculling seems to reduce the effectiveness of the arm pull. That led to results that were both straightforward and surprising.

"All things being equal, our data show that the deep-catch stroke is far more effective," Mittal says.

Using contemporary terms in a video interview, Mittal says, "The deep catch is as straightforward as it can get. You put your arm in the water, you put it as deep as possible into the water, and push it back as hard as you can, while keeping your palms perpendicular to the direction you want to move." To some, this description might paint a confusing picture. For the purposes of this article, we'll focus primarily on the deep-while-perpendicular concept.

The recommended emphasis on pull path and palm pitch are now considered fundamental aspects of proper freestyle technique

Freestyle propulsion is still an amazingly complicated issue. For simplification, clarity, and convenience, we've separated the Johns Hopkins findings into three sections.


The path of the arm is the most noticeable difference between the propeller and paddle motions, and the most important. Propeller arms follow a visually distinct out-in-out path from front to back. Paddle arms travel a line that is nearly linear. Picture the two hand paths from entry to exit occuring along two vertical planes existing in space at shoulder width.  From entry to exit, the two paths are parallel and nearly equidistant.


Pitch is more subtle than path. Unless a backward-facing palm pitch is maintained throughout the hand path, hand forces are misplaced. Keep in mind that no attempt is made to push the hands back through the water; instead, the hands remain angled back against the water. The single biggest key to maintaining correct backward pitch is to keep fingertips pointed down for as long as possible.

Premature release of the water is the biggest error plaguing Masters swimmers.  Letting go of the water too soon creates increased stroke counts, diminished thrust forces, and an ineffective motion.


Pressure is the least visible but most necessary factor of the freestyle pull. Even when the hand follows a perfect path, with perfect pitch, the swimmer will not swim fast unless the arm accelerates from front to back. It's been found that the most efficient swimmers do not accelerate their hands and forearms to maximum velocity until the middle or final segment of their underwater strokes.

In a 2004 study of hand forces and velocity, exercise physiologist and professor of biomechanics at Indiana University Rod Havriluk confirmed that swimmers are faster when they progressively increase their hand force.  In addition, swimmers who exert more hand force swim faster than swimmers who exert less hand force.

When taken in total, and dealing only with propulsive arm forces, path, pitch, and pressure are the basics of a perfect freestyle - so much so that a lack or a reduction of any of the three creates major deficiencies. On the other hand, significant gains in any of the three - big or small - lead to guaranteed improvement.

Please accept the challenge of change and try something new. If it feels different, that's good. Change is occurring. If your pull isn't different, then it's the same. And, hang on to your hats for this one folks: you might have to first slow down before you can speed up. Be patient, remain purposeful.

"All things being equal, our data show that the deep-catch stroke [paddle] is far more effective." - Rajat Mittal

Arm should enter at shoulder width, palm down, continuing forward into locked position at surface. During the middle of the arm motion, the elbow should be bent to nearly 90 degrees, just outside the shoulder plane.
The shoulders remain close to the water surface and drop to only 30 to 35 degrees from horizontal.
Keep your fingertips pointed to the floor and not toward the side walls.
When your hand enters and reaches down to its deepest point, you should feel water flowing upward from fingertips to wrists and forearm.
As your hand is exiting the water and moving up toward the surface, you should feel water flowing down from your forearm and wrist toward your fingertips.

More articles on paddle vs. propeller