Bodysurfers are slow. In the world of wave riding, we are at a clear disadvantage. Surfers, spongers, mat’ers, and SUPers all move faster in the water. This is an objective fact. The design of these devices give the user increased flotation, which in turn reduces drag. We, dedicated watermen, wanting to be conscious of our own efforts, look to maximize the efficiency of our movements through water. We can borrow knowledge from swimming science and infuse it with our own purposes to increase proficiency in our craft.
Part 1: Kick
The first and most obvious driver of acceleration is the bodysurfer’s kick. In typical swimming, the athlete’s propulsion is approximately 80% arms and 20% legs. This ratio changes significantly when you throw a pair of fins on that same person. Given the more than doubled surface area of the fin-covered foot, we can easily tilt the conversion to 50-50. Bodysurfers should rely on their kick for other reasons as well.
We aren’t swimming in a flat pool. Bodysurfers attempt to propel themselves onto the face of a curved wave. When we use our arms we change the shape of our upper body and risk creating drag and losing sight of the wave. Beginners often use their arms for too long, taking one too many strokes into a wave.
Some people choose specific fins adjusted to their preferred kicking style. Generally, we can describe fins in terms of how much leg drive it takes to move them. The longer and stiffer fins take longer and stronger strokes to “get moving,” while the shorter and more flexible fins are quicker to move and provide less propulsion per kick. A rider’s choice of fin is often based on the size of waves they will be riding, but ultimately what we do know for certain, is that there is a direct correlation to how much energy is exerted through kicking and a bodysurfer’s acceleration. To improve your kick power you can complete workouts focusing on the specific muscles involved in swimming (listed below) or you can bodysurf more.
Gluteus Maximus (butt muscles), Abductor magnus (groin)
Quadriceps (front of upper leg muscles), Hamstrings (back of upper leg muscles), Gastrocnemius (calf muscles), Tibialis Anterior (shin muscle), Abductor Hallucius (foot muscles), Abductor Digiti Minimi (foot muscles), Flexor Digitorum Brevis (foot muscles).
Part 2: Drag Reduction
Once you have your motor running, you can shift your focus to the art of reducing drag. The amount of resistance of an object can be calculated through the following formula:
R = 1/2 DpAv^2
R is Resistance, D is the constant for the viscosity of the fluid, p is the density of the water, A is the surface area of the body traveling through the water, and v is the velocity of the body.
As you can see from the equation, the velocity is squared. This leads to an exaggerated effect of the velocity on how much resistance a body receives in the water. The velocity of a body through water is exponentially “pushed back” or resisted. With this understanding, we look at other systems for drag reduction.
The body of a dolphin is a great example of low trim. They are able to fly through the water due to evolutionary adaptations in their physiology. The dolphin’s most forward appendage is smaller than the rest of its body. The nose disrupts the water with less resistance than if the dolphin had a large, round cranium like humans. For this same reason, we see swimmers start their race in the streamline position (shown below).
In following with nature, the swimmers are pulling their body into a tight formation, maximizing the momentum from their jump into the pool. It reduces their surface area and with this in mind we take a page from the swimming coach’s book. It all starts with the forward hand in a motion I call “the reach.”
When you are in position and starting your ride down the wave’s face, a long reach with your forward hand starts a chain of physiological adjustments that all help to reduce drag. To be precise, the reach of your hand should be making contact with the surface of the ocean. Your forward shoulder will follow suit and the angle between your arm and torso will increase, pulling that section of your body into a tighter line. While your arm and shoulder are flattening toward the surface of the ocean, your lower half will be drawn upwards pulling your whole body into a more horizontal position. As we established earlier, the more horizontal we can make our bodies, the less drag we enact upon it moving through the water.
Large surf teaches us another lesson in reducing drag. What could be better than reducing your surface area? Eliminating contact with the water all together. Bodysurfers who have managed to negotiate bigger waves can attest that when they really get movin’, their body is fully planing. In this state, water is only “dragging” on the parts of the body still in the water and our maximum velocity is greatly increased.
Bodysurfing provides an experience for athletes to be lost in the movements of Ocean. For lifelong swimmers many of these technical tenets come naturally, but no one swims perfectly. There are subtle manipulations of body posture that can mean the difference between a perfect in-and-out and a trip over the falls. As each rider navigates the wide, blue ocean, we can find the techniques that serve our purposes alike. In any case, a deeper understanding of our bodily interaction with the Ocean is always a worthwhile endeavor.