The zipper drill is a swimming technique drill that requires an athlete to slide the thumb of their recovering arm against the side of their body from hip to armpit. It encourages an overly high elbow, a compact arm, and a slow motion during the recovery phase of the freestyle stroke. It also promotes an early hand entry into the water. The drill is a leftover relic from swimming in the ‘70s and ‘80s, when a compact stroke was believed to be the most efficient way to swim. Today, it’s time to understand why we should retire the zipper drill from the pool deck once and for all.
Breaking down the zipper drill
Let’s start by looking at the recovery phase and zipper drill from a biomechanical assessment. The shoulder is the most active joint during recovery. It moves the entire arm from the finish at your side to the forward extension overhead. This is a very repetitive movement, performed over 1,200 times during an average 2000-yard workout. The ball and socket joint in the shoulder is very susceptible to impingement, overuse, and injuries when put in an unnatural position.
When performing the zipper drill, the head of the humerus bone (the ball) is jammed into the glenohumeral joint (the shoulder socket), putting pressure on the supraspinatus (part of the rotator cuff) and many other ligaments in the area. While the zipper drill can quickly lead to shoulder impingement, a wide arm swinging motion can take all the pressure off the shoulder joint during recovery. By keeping the arm relaxed and swinging the hand in a wide arc around the body (similar to a butterfly stroke recovery), there is no additional strain on the joint.
A wide arm-swinging recovery is the technique used by most successful swimmers and triathletes because it is the quickest way to swim. A swimmer’s arm can only provide forward propulsion while it is under the water (during the catch and pull phases). Therefore, the recovery phase has only one assignment: Return the arm to the water as quickly as possible to allow the next stroke to begin. Test this concept by letting your arm hang down at your side and then lift it over your head as quickly as possible. Is your first reaction to drag your thumb along the side of your body? Or does it feel a lot easier and quicker to just keep your arm straight and swing it up to the top?
Typically the arm is straight at the finish of the stroke next to the thigh; it’s also straight when it enters the water above the head. The quickest way to move between these two parts of the stroke is to swing the arm around the side of the body in an arc. Create an obtuse angle (greater than 90 degrees) with the elbow by relaxing the wrist and forearm away from the body as it moves forward. Let the arm drop into the water at the front of the stroke, and inertia from the arm swing will naturally rotate the torso and position the body for the next stroke.
The hand position in the zipper drill also encourages an early hand entry into the water. Because the hand is sliding forward next to the head, it tends to enter the water near the head. This is very detrimental to the athlete’s forward propulsion. As the hand and arm push forward into the water, the athlete will be pushed backwards—akin to taking a backwards stroke while paddling a canoe. A wide and straight recovery allows the hand to stay above the water until the arm is in front of the shoulder. At this point, the arm simply drops into the water in a fully extended and streamlined position to prepare for the next stroke.
For triathletes who start to swim later in life, flexibility is also a big factor. Most adults do not have the range of motion in their shoulders and upper back to execute the zipper drill without a struggle. Without incredible flexibility, emphasizing a high elbow and compact arm recovery can overwork and strain the neck and upper back muscles. Instead, athletes with limited range of motion should let the recovery arm swing wide so that the upper back, neck, and shoulders are able to stay relaxed.
Furthermore, conditions are rarely perfectly flat and calm in open water. The surface is stirred up by wind, waves, boat wake, and other swimmers in the water. Triathletes with a wide arm recovery are less likely to be negatively affected in rough conditions because they can easily lift their hands higher during the recovery to avoid the uneven surface water without utilizing an extreme angle. This flexibility of being able to change hand and arm position is also good for avoiding other swimmers and obstacles in the water as conditions (inevitably) change during a tri swim.
Do this, not that
The next time you are in the pool, try experimenting with a wider recovery phase of your stroke. Do you feel more relaxed? Is your stroke tempo quicker? Do you have less strain in your shoulders and neck? If the answer is yes to any of these questions, please join us in permanently retiring the zipper drill from your training sessions to save your shoulders and swim more efficiently in the future. Trying to break the habit and transform into a more evolved (and well-rounded) open-water swimmer? Try these zipper-replacing drills below:
Use a 12-inch length of half inch round PVC pipe to do a no-cheat version of catch-up drill. Hold the stick 6-8 inches below the surface of the water with your arms extended forward. Swap the stick from one hand to the other while performing a catch-up drill. Don’t pause or slow your arm during the recovery until they drop into the water and grab the stick. Swing your arms wide and relaxed during the recovery. Experiment with different arm recovery positions to observe the differences.
Wide thumb drag drill
Most fingertip drag drills look similar to a zipper drill with an exaggerated high elbow and the hand recovering close to the body. Try a wide arm recovery drill by dragging the tip of your thumb along the surface of the water. This requires the elbow to be in a more obtuse angle and forces the hand to swing in a wide arc away from the body resulting in a more comfortable shoulder joint.