Focus on Force

Science defines swimming speed (S) as the result of propulsive force (F) multiplied by the turnover rate (R) minus the amount of drag (D). As a simple math equation, it looks like this:

S = FR – D.

You want the value of S to be as large as possible, so you need to increase force and rate while decreasing drag.

Drag is the biggest factor in our equation, which explains why swimmers who are smooth and streamlined almost always outpace muscular brutes who flail away with fast cadences and flawed form. We’ll talk about drag reduction in more detail in additional STREAMLINES articles, and nearly every SWIMMER magazine technique feature also provides tips for improving your streamline, but this discussion focuses on force and rate.

Properties of Propulsion

To state the obvious, you apply propulsive force with movements of your arms and legs. Your hands and forearms work together as paddle assemblies that push backward through the water to generate thrust. Breaststroke kick applies force in a similar way, while flutter and dolphin kick create thrust with up and down motions that force water backwards, more like a boat propeller would.

While a propeller can create thrust by cycling at a constant speed, paddles don’t work that way. A paddle must continually accelerate to apply propulsive force. The following example is a simplification of the actual physics, but it works well to help us visualize the process:

• Water is a fluid; when you push it, it moves.
• Once water is moving, anything moving in it at the same speed simply floats along, with no additional force created.
• Therefore, if you want to generate thrust throughout your entire stroke, you must move your paddle faster and faster as the water you’re pushing speeds up. Your hand speed must remain greater than the speed of the water it’s pushing, which means you must accelerate (i.e., continually increase your hand speed throughout the duration of your pull.)

In other words, an effective swimming arm stroke will not move at a constant rate like the second hand of an analog clock, or like the pedal of a bicycle. There are three distinct speed zones during a complete stroke revolution:

• The recovery and entry, which is a relaxed effort at a constant speed.
• The catch, which is a brief interlude without movement as you establish your position to begin the pull.
• The power phase, which is where your hand and forearm explosively accelerate from the catch position throughout the pull to the beginning of the recovery.

Turnover Tradeoffs

At first glance, our speed equation implies that the fastest possible stroke cadence would always result in the quickest swim. If force and drag remained constant at all turnover rates, this would be true—but the fact is that speeding up your arm stroke can cause a reduction in force and an increase in drag. Pitfalls of overclocking the cadence include:

• Sloppy hand entry that creates turbulence (bubbles) during the catch, resulting in thrust reduction during the pull
• Alterations in body position and alignment from angular momentum created during the recovery, resulting in additional drag from distorted posture
• Pulling-motion form failure because of the muscles’ inability to hold proper paddle configuration at the higher speed.

You want to find that optimal cadence (the “turnover speed sweet spot”) where you can achieve the highest stroke rate while maintaining your best form and force production.

Enhancing the Equation

When you’re tired or in the middle of a long distance set, it’s easy to fall into the “clock movement” turnover trap; you go through the stroke motion at a constant rate with very little force applied on the back half of the pull. That’s why it’s important to regularly perform specific activities to establish the recovery-catch-acceleration speed zones as deeply-ingrained habits.

Strength training will increase your ability to apply force, and you can train your brain to consistently apply acceleration using drills like these:

• 5 x 50, with the first 25 freestyle and the second 25 backstroke. Perform these slowly, and concentrate on the feeling of starting with a clean catch and then accelerating your hand through the entire pull. Think of explosively throwing the water toward your feet during the propulsion phase, then relaxing through the recovery. If you prefer, take an extra six kicks between each arm stroke to allow yourself time to really focus. Your arm muscles should feel pressure throughout the pull.
• 5 x 50 breaststroke, with the first 25 focused on the arm pull and the second 25 focused on the kick. When you kick, make sure that the explosive energy of the acceleration is applied to bringing the feet back and together, rather than into the recovery (heel lifting) phase.
• 6 x 25 butterfly. On the odd ones, focus on the muscular exertion in the pull acceleration phase. On the even ones, focus on applying energy to the kick while relaxing the arm recovery.
• 8 x 25 sprints (choice). Focus on force and power applied throughout each pull, holding the fastest stroke cadence you can without getting sloppy. Take enough rest to fully recover so that you can exert maximum effort on each one. If your arms aren’t feeling fatigued enough from your exertion, feel free to throw in 10 pushups before each 25.