Analysis of the Underwater Pull – Phase I: Lift

Lift is simply due to forces that elevate the level of the human body in the water. Since water is about 800 times denser than air, so long as we are on the surface, the more of the human body that is in air and the less in water, the less frontal drag will be encountered when moving forward. The difference between frontal drag forces in air and water are so profound, that even the slightest elevation of the body in the water can reduce overall frontal drag significantly. A good example of this fact is found while swimming in salt water, which is slightly faster than swimming in fresh water. The added buoyancy of the salt elevates the body and reduces frontal drag.

Short of wearing a wetsuit, the only two natural contributors to lifting the body while swimming are the arms and legs. While using a six-beat kick, the legs contribute three times the number of lift efforts to each arm pull. However, the arms are capable of making a huge contribution to lift, but that occurs only at the beginning of each underwater pull, from the 12 o’clock to the 3 o’clock position on the ‘glare’ clock. During that time, the arm and hand are in a lesser frontal drag position, stretched out in front, close to the line of motion of the body.

There are two reasons why the hand/arm create lift in the early phase of the underwater pull. The first is from Bernoulli’s principle, which requires the relative speed of water above the arm and hand is greater than below it, resulting in a greater pressure below to create lift. This type of lift is greatly dependent on the speed at which the arm and hand are moving through the water. Unlike an airplane, which requires tremendous speed in order to lift it off the ground, one can achieve lift in the water from this mechanism at relatively slow speeds. Yet the faster one is moving in the water, the more of this type of lift occurs. Since the outstretched arm and hand in front are responsible for creating some of this type of lift (the rest occurs on the body or legs) and at this particular moment in the cycle the front arm/hand does not contribute at all to propulsion, that means the propulsion needed for the Bernoulli lift is coming from either the legs only (shoulder-driven freestyle) or both the other hand/arm and the legs (hip-driven freestyle). It is for this very reason that hip-driven freestyle, which requires a longer push out front with the arm/hand and delays momentarily reaching the propulsive phases, results in more Bernoulli lift, particularly with a strong kick. The other hand is contributing to the propulsion at this moment. In addition, the kick itself also provides much lift from its force downward.

The second means of creating lift with the arm/hand is also by simply applying a downward force. This motion always occurs in either a hip-driven or shoulder-driven technique because it is necessary to get the hand into a deeper position where it can move backwards, creating propulsion. The difference is timing, as the hip-driven freestylers will delay this downward force while driving forward with strong legs and a bigger hip turn (rotation), while the shoulder-driven freestyler requires an immediate downward force after the hand entry, resulting in a higher arm stroke rate.

In my example, using a shoulder-driven technique, the hand remains in the lift position for .35 seconds, longer than all of the other phases, including the above water recovery. In the hip-driven technique, where the stroke rate may slow to 60 per minute, the cycle time slows to 2 seconds (from 1.1 seconds in shoulder driven) and the duration of the hand/arm in the lift phase would be about l to 1.25 seconds, longer than the entire cycle time of the shoulder-driven freestyler.

Regardless of which freestyle technique is used, the way in which this downward force of the arm/hand is initiated has a huge bearing on how much frontal drag is caused from the remainder of the arm motion underwater. In particular, it really matters what is happening with the upper arm, from the elbow to the shoulder, as that part of the arm is moving forward for 2/3 of the entire duration of the underwater pull (or ¾ of the underwater pull time for the hip-driven swimmer). Once the hand reaches 3 o’clock, it starts moving backward and no longer contributes to frontal drag (except slightly during the release phase when it is moving forward again). The upper arm continues to move forward contributing to frontal drag until the hand is past 6 o’clock. At that point, the upper arm is tucked into the swimmer’s side, moving backward for a brief moment before the release. One can choose either to pull in a more natural way by pushing down with the entire arm from the shoulder to the hand to create this lift from 12 o’clock to 3 o’clock. Not only will this motion create more lift, it will also put the arm in a more favorable biomechanical position for the second and third propulsive phases of the pull. However, this is not the way the fastest swimmers pull. So what is the catch (no pun intended)? This motion also causes the highest amount of frontal drag by immediately putting the upper arm off axis (this means it is not in line with our body’s motion). This deeper pulling pathway also keeps the upper arm off axis for a longer period of time. The result is in an increase in frontal drag that more than offsets the amount of additional power and lift that this motion allows. It is like putting one’s foot on the gas and the brake at the same time. The net result is a slower swim and a more exhausted swimmer.

The better option for the lift phase of the underwater pull is to create the lift motion with the forearm and hand only. Leave the upper arm moving more or less straightforward, elbow near the surface, while the hand moves from 12 o’clock to 3 o’clock. This position is known as early vertical forearm. If one is rotating the body properly, whether using a hip-driven or shoulder-driven technique, this motion puts the lead arm initiating the underwater pull into an extended shoulder position. That means that the arm is actually angled at the shoulder joint behind the body (negative angle). In this position, the arm is simply not as strong as it is in a neutral or positive angle, pointing forward. Fortunately, as the body counter-rotates while the hand/arm go through the pulling motion, by the time the hand is into the propulsive phase at 3 o’clock and begins to move backward, the shoulder joint is now back into a positive angle. Not as much power is sacrificed during this crucial propulsion phase as one might think. Yet, even though by using this pulling motion, one reduces both lift and some propulsive power in the arm, one still ends up being better off because the upper arm in this motion creates much less frontal drag. Bottom line: Reducing frontal drag trumps power.

In order to swim fast, you need the lift from both your arms and both your legs. When it comes to getting the lift from the arms, however, use the hand and forearm, not the upper arm. This motion creates the high elbow or early vertical forearm position that reduces frontal drag and is paramount to fast swimming.

Yours in swimming,

Gary Sr.

Underwater Pull Video Series:

5 Responses to Analysis of the Underwater Pull – Phase I: Lift

  1. Jangaroo2010

    You stated that there’s only two ways to provide lift. What about Number 3 by breathing at the top part of your lung capacity for those that blow out and empty thier lugs? What about Number 4 by a subtle change to the orientation of the head to plane up the head aileron without going  too high which becomes a flat kick board in the flow?

     
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  3. Trevor Weir

    I also agree with Jangaroo2010, but there is another factor which does NOT come into play at low speed but at 2.5-3 KM/H its a big factor.

    Jangaroo2010 mentioned orientation of the head and where the head goes so doth the chest follow.

    The analogy here is that if you’re being dragged behind a fast boat, its the angle of your chest relative to the surface of the water that that will either lift you or force your body downwards.

    Look at it as hydroplaning and whenever you stop to talk about lift and drag remember that these can be very different forces at different speeds.

    So much so, that for beginners, its not a conversation to even bring up but for speedsters who can attain 3-7 Km/H in the water its a really, really good thing to know.

    I would also like to let you know that Phase 3, very much looks like the swimmer is *sometimes* lifting water, which following newton’s laws this means they are pushing themselves down.

    I have corrected this on hundreds of swimmers by having them push the water out to the side with a gradual rotation of the wrist so that they are NEVER lifting water which is a waste of energy in most cases.

    Anytime, I catch myself lifting water, I immediately change my stroke style.

     
    • garyhallsr

      Lift can be provided by both Newtonian forces or by the Bernoulli effect. At the speed of most swimmers, I believe the Bernoulli effect (to which you both may be referring) is minimal.
      Increasing the air in the lungs does increase the swimmer’s buoyancy but does not create lift. Curiously, most elite swimmers will release air through the nose after a breath. If the air bubbles follow the path beneath the body, they will now not only still provide lift, but also likely reduce frontal drag. Cruise ships and the Empire penguins of the Antarctic use this technique to move faster. So the air may serve a swimmer better under the body than in the lungs.

       
      • garyhallsr

        sorry..the air bubbles will increase buoyancy but not lift.

         

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