Athletic development specialists dedicated to the art and science of excellence in movement

Deceleration Skill Mastery for Swim Power: The Kinematic Sequence in Long Axis Strokes

Great swimmers flow through the water with effortless power.  Finding that sweet spot of efficiency in the water is one of the most elusive athletic skills.  To novices, fast swimming takes an almost mystical quality.  Fortunately, research in other rotational sports yields clues to help crack the code.   One area of power generation often overlooked in the water is the importance of segmental deceleration.    

To understand deceleration in swimming, let’s step away from the pool for a moment.  Imagine you are in a car in motion.  The car comes to a screeching halt.  What happens to the occupants?  They will be launched forward even though the car is stopping (hopefully they are wearing seatbelts!).  We can use this same concept to explain the transfer of energy through the body while swimming. 

Swimmers are often told to “get onto your side” during freestyle and backstroke.  Instructors use the image of parallel railroad tracks onto which the body shifts in an alternating pattern guided by arm and leg movements.  However, more important than getting onto your side is how you get there.  For maximum power and balance, the body must not turn all as one unit but instead with each segment of the body activating and then decelerating in a coordinated sequence.    

 This coordinated sequence is sometimes called the “kinematic sequence” in biomechanical research.  Biomechanists studying golf, baseball, tennis and other rotational sports have studied the heck out of this stuff.  (Side note: There are several reasons why very little hard data exists in swimming. There is actually more literature on the kinematic sequence of fish swimming than of humans swimming.  One is that the equipment is quite expensive on land; adding a waterproof feature certainly ain’t cheap.  Two, there isn’t nearly as much money at stake in swimming as in other sports where professional athletes make hundreds of millions of dollars.  In terms of prize money, Michael Phelps makes less than a marginal pro in any of the above listed sports.  Other sports have benefited from the trickle-down effect of technology.  Finally, the swimming world has been so obsessed with suit technology in the last decade that research into other areas of the sport has been somewhat neglected.  The neglected areas have far more applicability to the non-elite swimmer than research into racing suit technology.)   

In any rotational sport, power begins from the lower body and works upward.  With a sound base from the legs, the pelvis, thorax, arms, and hands accelerate and decelerate on their own coordinated schedules.  Most swimmers get the acceleration part (“snap the hips”; “rotate the shoulders”).  Acceleration in swimming is wasted effort if not matched with appropriately timed deceleration.

We know from studying kinematic sequence graphs (see the picture above) that the pelvis helps initiate rotation through acceleration.  To transfer energy to the next rotational segment (the thorax), the pelvis must decelerate.   Just as the deceleration of the braking car helped thrust its occupants forward, the deceleration of the pelvis allows energy to transfer upward to the thorax.  Deceleration of the thorax allows for the transfer of energy into the arms. 

Swim literature relatively sparse on this particular issue.  However, here’s one interesting note from some research out of the United Kingdom (Psycharakis S, Sanders R. Body roll in swimming: A review.J Sports Sci.Feb 2010:1-8.)

“The main research findings can be summarized as follows: swimmers roll their shoulders significantly more than their hips; swimmers increase hip roll but maintain shoulder roll when fatigued.

More is better right?  Not quite.  Let’s revisit the acceleration/deceleration concept.  The increase in hip rotation could mean the subjects had difficulty decelerating or stabilizing the hips to “get out of the way” for the shoulders to rotate.  In golf, we know that one key to power is maximizing the differential between hip and shoulder rotation.  In the study above, hip and shoulder rotation converged.  As these rotational components converge, the swimmer is required to call upon less efficient mechanisms for propulsion.  As such, instead of energy being transferred efficiently upward through the body, the upper body must work harder to compensate for the loss of energy that would have been provided by the normal deceleration of the hips. 

What does all of this mean for instruction?  First, the swimmer must own the ability to disassociate independent segments of the body.  In the best golf swings, the pelvis and the shoulders actually work in two separate directions for a few brief moments.  As the pelvis turns toward the target the thorax continues winding up.  Once the swimmer owns the skill of being able to disassociate each segment of the body, we then specifically train acceleration and deceleration patterns in proper sequence.  Swimmers must understand that basic weightlifting won’t be very useful for developing this skill set.  


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