Gary Hall Sr. is now a regular contributor to Swim Swam .com. Here are his first few published articles discussing The Fundamental Laws of Swimming.
At The Race Club, we pride ourselves in teaching fundamentals and paying attention to details. In order to excel in swimming, arguably the most technique-sensitive sport of all, one needs to be mindful of millimeters, degrees and tenths of seconds. A few millimeters away from the correct head or elbow position, a few less degrees of ankle flexibility or hip rotation, a few tenths of seconds in delay of a pull or a kick can lead to…well, the loss of a race.
Understanding the fundamentals of swimming requires knowledge of the basic scientific laws that govern the technical aspects of our sport. For the most part, these laws for the underwater and surface movements are Newton’s three laws of motion, redefined for a swimmer.
NEWTON’S LAWS OF MOTION
The force that Newton defines in his second law of motion, the vector sum of the propulsive forces (those that propel us through the water) and the drag forces (those that slow us down) ultimately determines our body speed or acceleration in the water. While it seems desirable to maximize propulsive forces and minimize drag forces, the reality is that we can’t always have it both ways. That is what makes swimming such an interesting sport from a technical standpoint. The motions of maximum propulsion do not agree with the motions of minimal drag…so we learn to compromise. And we learn that although there are commonalities of good technique, there is not necessarily one single best way of swimming fast for all swimmers and for all distances.
THE BERNOULLI EFFECT
There are other laws that affect a swimmers speed, such as the Bernoulli effect, that likely provides some lift (upward force) to a swimmer, or the law of conservation of energy that impacts the way we recover with our arms, head and body above the water.
In considering all of the motions of a swimmer that may improve the likelihood of swimming fast, one must also consider the biomechanical impact of those motions. Will they lead to injury? After all, as human beings, we are really not well engineered for moving fast in the water. So in redefining ourselves as aquatic mammals, we must be careful to consider all aspects of strength, flexibility and motions in our endeavor to swim fast safely.
I hope that you will enjoy some of the discussion we have in our Race Club fundamentals lecture where we share some ideas on how to reduce frontal drag, how to increase propulsive forces and how to best obey that immutable law of inertia. You will find it on the link below.
Drag refers to the forces that slow us down in the water, as we are moving forward. I consider frontal drag the number one enemy of the swimmer. In the medium of our sport, water, which is about 800 times denser than air, drag forces impact the speed of a swimmer at significantly lower speeds than in air. In addition, drag forces in water are extremely sensitive to minute changes in our shape and are exponentially related to our speed. That simply means that the faster a swimmer becomes, the more critical the technique is.
THERE ARE THREE DIFFERENT TYPES OF DRAG FORCES THAT SLOW SWIMMERS DOWN; PRESSURE (FORM) DRAG, SURFACE (WAVE) DRAG AND FRICTION.
In a study done in 2008, Mollendorf, Termin et al showed that all three types of drag affect the speed of swimmers that were being towed on the surface (1). At slower speeds (less than 1 meter/second), pressure drag was the biggest contributor to slowing, while at higher speed, friction became more important. Adding the motions of the arms and legs of a swimmer doing any stroke complicates the contributions of these drag forces by constantly changing the swimmer’s shape and speed. Nonetheless, coaches and swimmers must be mindful of the details that help reduce these forces in order to attain the best possible performance.
FRONTAL DRAG FORCES ARE SO IMPORTANT IN SWIMMING, THAT THEY OVERSHADOW THE IMPORTANCE OF PROPULSIVE POWER. POWER IS STILL IMPORTANT, BUT IN THE WORLD OF SWIMMING, FRONTAL DRAG TRUMPS POWER.
At The Race Club, we pay attention to the minute details that will impact frontal drag. In freestyle alone, I can think of ten different ways a swimmer can reduce frontal drag. The following is a Race Club video link that highlight a few of these and will help you slip through the water with less resistance, reducing your frontal drag, and increase your swimming speed.
PROPULSIVE FORCES & FRONTAL DRAG FORCES
Sir Isaac Newton’s three laws of motion are as applicable today to a swimmer as they were centuries ago when he formulated them. However, for me it is easier to conceptualize the application of the three laws by separately considering the forces that move us through the water (propulsive forces), the forces that slow us down (frontal drag forces) and the law of inertia, which tells us it is most efficient to maintain a constant speed by keeping the forces of propulsion and drag equal.
The propulsion of a swimmer is derived primarily from two sources, the hands and the feet. However, there is another motion involved in the freestyle and backstroke of a fast swimmer, other than kicking and pulling, that is vitally important to generate more propulsion; the axial rotation of the body from side to side.
FREESTYLE & BACKSTROKE
Although coaches and swimmers commonly believe that one of the reasons fast freestlyers and backstrokers rotate their bodies along the axis of their motion is to reduce drag, I don’t agree. If that were true, we would see a substantially faster kicking speed on our sides than we do on our stomachs or backs, and that is simply not the case.
Another common theory for why we rotate our bodies in freestyle and backstroke is so we can reach out further on each stroke. While that may be true at the finish of a race (particularly freestyle), I don’t believe the extension of the arms on the recovery of a rotating swimmer is any further than on a non-rotating swimmer.
MECHANICAL & BIOMECHANICAL
There are two reasons for rotating the body during freestyle and backstroke. One is mechanical and the other is biomechanical. The biomechanical reason is that by rotating our body to initiate the underwater pull, we put ourselves into a more favorable position to use our back muscles, particularly the large latissimus dorsi muscle. That will make our pull stronger.
The mechanical reason is that by counter-rotating our bodies during the underwater pull we can create a significant force to pull against. In other words, we are no longer pulling against just water molecules that are relatively motionless. We now have the water, plus whatever force we can generate with the counter-rotation of our body. The amount of that force that we get to pull against is related to our mass (weight) and to the angular velocity of our body’s rotation (how fast we rotate).
The rotation of the body doesn’t just happen. A swimmer has to make it happen and that requires a lot of core strength and work. When the rotation is fast and timed well, it is worth the effort, creating a substantial force that enable the swimmer to cover more distance with each stroke.
No one said swimming fast was easy. Here are some of our favorite drills:
At The Race Club, inertia is the third fundamental law we teach our swimmers. Although Newton is often credited for this law (his first law of motion), it was actually Galileo that was the first to conceptualize inertia.
A MOVING BODY RESISTS CHANGING ITS SPEED
The definition of inertia is a body in motion tends to want to stay in motion. In other words, a moving body resists changing its speed. The same holds true for a car on the freeway as it does for a body swimming down the pool. The frontal drag forces are working to slow us down whenever we are moving, so to maintain a more constant speed requires that we maintain a near-constant propulsion. Although this takes work, it actually requires a lot less work than if we were to stop or slow down appreciably and try to regain the original speed. A good example is when you completely misjudge the wall on a flip turn, pushing against nothing but water. The result is a total loss of speed and the effort to get back to race speed from this dead stop is overwhelming.
THE FREEWAY STROKES
There are really only two inertia strokes; freestyle and backstroke. I call them the freeway strokes. Because of the way in which we generate propulsion in fly and breast, abrupt changes in body speed are unavoidable. Consequently, these two stop-and-go strokes are both difficult and inefficient. Yet, even in those strokes, the law of inertia still applies.
There are only three things I can think of one can do to comply with this law of inertia in freestyle and backstroke, in order to keep the body speed more constant. The first is to kick with a six-beat kick, trying to generate some propulsive force on both the down and the up kick.
The second is to increase the pulling stroke rate (decrease the cycle time). For a freestyle sprinter with a stroke rate of 120 strokes per minute (60 right arms and 60 left arms), the cycle time is one second. The propulsive phase (when the hand is actually moving backward) in front and back quadrants is about .35 seconds. For both hands that means that .7 seconds of the one-second cycle time (70%) is spent actually propelling the body forward. The rest of the time the hand is either lifting the body or recovering. Either way, it is in propulsive ‘down time’. The faster the stroke rate, the less propulsive ‘down time’ and the more constant the speed.
DISTANCE SWIMMERS MUST HAVE A STRONG 6-BEAT KICK
For distance swimmers, like Sun Yang, who use a stroke rate in the middle of the 1500 of 60 (cycle time 2 seconds), the time in propulsive phase is still .7 seconds, but that represents only 35% of the total cycle time. That does not bode well for the law of inertia. For this reason, hip-driven (slow stroke rate) freestylers must have strong six-beat kicks to obey this law.
REDUCE FRONTAL DRAG
Finally, the third way to abide by this fundamental law of maintaining constant speed is to reduce frontal drag as much as possible. This is accomplished by keeping the head in alignment with the body and getting the head underwater at the crucial time of hand entry, keeping the body and legs in as straight a line as possible and by pulling under water with a high elbow position. In testing myself with the velocity meter using arms-only freestyle, with a deep pull, the body speed dropped by nearly 40% from hand entry to the initiation of the propulsive phase (.3 seconds in a sprint). With the high elbow pull, the body speed dropped by 30% during the same phase. While that may not seem like a huge difference, when it comes to inertia, every bit helps.
George Bovell demonstrates some creative drills for fast swimming: https://theraceclub.com/videos/swimming-technique-videos/
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