The Science Behind Swimming Activity

Science surrounds everything that humans do. This includes moving through water in a sport commonly known as swimming. It seems simple enough, but there are really many components that make swimming the sport that it is today. The physics behind swimming mainly have to do with buoyancy and drag. There is science everywhere, from buoyancy, to streamlines, and dolphin kicks, to swimsuits, goggles, and even pruney fingers.

Swimming would not be possible without buoyancy. Naturally, flotation is necessary for swimming. The Archimedes’ Principle helps to explain buoyancy. It states that when a body is immersed in a fluid, it experiences an upward buoyant force equal to the weight of the fluid displaced (Swimming Science Bulletin). When an object is placed in water, the water pushes upward against it, effectively canceling out the power of gravity. Swimmers swim horizontally so that there is an upward force on more parts of their body which evidently makes it easier to float. Weight is often times used to measure buoyancy. Neutral buoyancy is achieved when the volume and weight of an object is equal to the volume and weight of the water displaced. During neutral buoyancy, an object neither sinks or floats. If the volume of an object is greater than the volume of the fluid displaced, it floats. There are a few other factors that can affect how a person floats. One of these definitely is the amount of fat in a person’s body. If they are swimming somewhere cold, it can definitely help with insulation, however it can also mostly help with flotation. Flotation can also definitely be affected by the density of water. Saltwater, for instance, generally is much denser than freshwater. This means that salt water can carry objects easier. Most of a swimmer’s energy is used to push water out of the way, and water must be displaced under and swimmer and to either side. Therefore, resistance can be reduced drastically with water going over the swimmer. Besides, the waves created on the surface of the water really create drag. This can be reduced by swimming underwater. This is why swimmers are the fastest underwater. They optimize their time underwater using streamline dolphin kicks. Swimmers also use swim suits to become more buoyant. There used to be a type of swimsuit that was polyurethane based that was banned. It covered much more of the body, but FINA decided that it gave swimmers too much of an advantage. The suit, often called a “rubber suit” provided too much buoyancy and was banned. Now, swimsuits do not aid with buoyancy much, instead, they work to reduce drag.

Drag is water resistance. Water resistance slows swimmers down, so, naturally, many things are done to reduce drag. With minimal drag, swimmers may reach a faster pace. Since discovering that swimmers are fastest when completely submerged, research has been done to discover how to optimize time underwater. It has been discovered that swimmers are fastest when they first push off of the wall. The momentum from that push moves a swimmer faster than any amount of strength alone, which is very important. To keep this momentum, an arm position known as “streamline” was created. In a streamline, a swimmer’s arms stretched above his/her head and one hand of the other. Water can flow easily past a swimmer in this position without creating much drag. In other arm positions, swimmers have to push against the water which only makes a swimmer move backwards. Swimmers want to move forward, not backwards, so pushing against the water creates the opposite of the desired effect. A good streamline is very important for all swimmers in order to swim fast because the momentum of the push off of the wall is important to maintain. Swimmers don’t build momentum when they swim because the water is pushing against them, so maintaining the momentum from the push off of the wall is very important. Streamlines are arguably the most important part of a race.

Another thing that swimmers do to optimize time underwater is a dolphin kick. To do a dolphin kick, a swimmer moves his/her legs at the same time in a motion that looks like a wave. Dolphin kicks tend to vary from swimmer to swimmer. Some swimmers will have very large and powerful dolphin kicks. Some swimmers will have very short and fast dolphin kicks. Swimmers choose the dolphin kick that they want based on their size and core strength, which is different for everyone. Also, some swimmers will dolphin kick on either side. USA Swimming dictates that swimmers may only dolphin kick to the fifteen meter mark on the pool. Some swimmers dolphin kick to this mark, and some barely dolphin kick at all. Those who are good at dolphin kicks will typically spend as much time as possible underwater. For some people, dolphin kicks are not very fast. This usually has to do with a lack of core strength. For these people, it does not definitely make sense to dolphin kick for fifteen meters when they would be much faster swimming above the water. Streamlines and dolphin kicks are incredibly important in swimming, and are often times undervalued. Many people consider them to actually be the fifth stroke because they are so important and used in every stroke.