Free Speed

CHAPTER 1

SIMPLE HYDRODYNAMICS

This chapter is based on science and the theory of Ernest W. Maglischo in his book Swimming Fastest.1

Energy conservation is a serious concern nowadays, and one area where you can witness this is in the current design of cars, which are aerodynamically shaped and fuel efficient. So how does that relate to swimming?

Firstly, you are not travelling through the air, which is approximately 830 times less dense than water, meaning that if you want to travel at speed you are going to be using a lot more of the body's energy. This makes efficiency vital. Secondly, by simply reducing the amount of space you take up in the water, you are reducing the drag factor.

As this book is aimed mainly at triathletes who, in general, have a good understanding of aerodynamics when riding a bike, I often use cycling as an analogy for hydrodynamics in swimming. Air and water are both classified as fluids. Consequently, the physical laws are the same for both, even though water is considerably denser. Therefore, like any object moving through the air, the faster it goes, the greater the resistance against it - commonly known as drag. This can be reduced by its shape (improving its aerodynamics) and applies to your body when swimming in water (hydrodynamics).

By understanding the biomechanics and physics of swimming and knowing how important a hydrodynamic position in the water is, you can learn to visualise how your perfect front crawl should look and feel. This is the first step in working towards your goal of being a faster and more efficient athlete. The main goal of the swim within a triathlon is to swim as fast as possible using the least amount of energy you can. It is only approximately 20% of the race.

Hydrodynamics in swimming are mainly governed by your body position. Going back to cycling, it is akin to being in the best possible aerodynamic position on an expensive time trial bike. Or like building an aerodynamic body for a car. Get this right and you are already taking the first steps towards becoming an efficient athlete.

BASICS OF DRAG

The resistive force that acts in the opposite direction to a swimmer's body is often known as drag. It is important to have an understanding of resistive forces, or drag, so you can minimise them, and therefore maximise propulsion. There are a few different types of drag forces, which basically all help to slow you down and require increased effort to overcome, thereby consuming more of the energy that you are trying to save to complete your race.

The key factors that determine the resistance drag you create in swimming are:

The shape or space a person makes in the water (frontal drag).

Limb movements pushing water forwards instead of backwards (pushing drag).

The friction between the body and the water flows that it hits (frictional drag).

The body's movement in the water also creates eddy currents that act against your forward propulsion.

FRONTAL DRAG

Simply put, the frontal shape your body presents to the water (in cycling, your body's frontal area) creates resistance, and the bigger the frontal area, the more resistance that is created. Also, the water movement in swimming creates what are called eddy currents, with water filling in behind you as you move forwards. These can tend to pull you back, as the hole behind needs to be filled. The less streamlined your body is, the more turbulence there is, leading to eddy currents working against you and slowing you down.

The following diagrams show two classic examples of how frontal resistance is increased.

Figure 1.1 shows how body alignment can greatly increase frontal drag by what is commonly known as snaking, often caused by the entering hand crossing the body centreline. Athlete 'a' has good body alignment, moving through a smaller space in the water; athlete 'b' has poor body alignment, with hips and legs swinging outside the shoulder line.

Figure 1.2 highlights that the greater depth you take up in the water, the more frontal drag you create, similar to sitting up on a bike, compared with being head down on your tri-bars. Your body may naturally be more dense (for example, bones and muscles weigh more than adipose tissue, and distribution will be different too), with women, for example, on average 1 percentage point less dense than men (the density of fresh water is 1.0 gm/cc vs 0.98 for men and 0.97 for women), which means that on average a man floats further down in the water. The buoyancy force, according to Archimedes, means that the body is subjected to a force equal to the weight of water displaced by the body - requiring more lift to counter it.

Athlete (a) has a good body alignment showing less space taken up in the water. Athlete (b) has poor body alignment with lower hips and a deep kick taking up more space in the water.

FRICTIONAL DRAG

As you move through the water it exerts a frictional force on the layer of fluid next to your skin. This is often reduced by wearing the latest swimwear or, in open water, a good quality wetsuit. Competitive swimmers will often wear drag shorts in training to increase drag for resistance, which also helps you to feel faster in competition when wearing your race suit.

PUSHING DRAG

A good example of pushing drag is when a swimmer has poor hand entry: slapping a forearm against the surface of the water and pushing it forwards along the surface which causes extra drag and slows the swimmer down. To help reduce this, keep all non-propulsive limb movements streamlined and soft to avoid them pushing against the water, by trying to slide them through instead.

WAVE DRAG

This drag force acts where the air and water meet and can be greatly increased in open water, especially on a windy day. When you move a part of your body at the water's surface, a wave is created. The force exerted on you by a wave is known as wave drag.

REDUCING DRAG

Good body alignment: keep your core locked (belly button to spine), your head as still as possible, minimising rotation when breathing and rotate your body as an entire unit, thereby minimising lateral movement.

Ensure that hand entry and arm recovery are relaxed and smooth: where possible keep your arms within the cross-sectional area of the body as they enter the water and slide them forwards through the water with the smallest and most tapered surfaces, fingertips facing forwards.

Avoid putting any pressure on the water on all non-propulsive movements, for example avoid pressing downwards with your hand before it reaches the catch position (technique covered in the next chapter).

Keep your kick as shallow as possible to maintain a good streamlined body position.

PROPULSION

Newton's third law of motion: whenever two objects interact, they exert equal and opposite forces on each other. This is often expressed as 'every action has an equal and opposite reaction'.

I agree with Ernest W. Maglischo's conclusions in his book, Swimming Fastest, that forward propulsion in swimming is mainly the effect of your limbs pushing backwards against the water. Therefore, until your hand and forearm are vertical to the surface of the water, there is little, if any, forward propulsion from any other actions, as stated in Newton's Third Law. The actions of pushing your hand and forearm against the water in a backwards direction will drive you forwards. This also supports the two most effective methods for swimming fast: early vertical forearm (EVF); and kayaking or Popov's method of swimming.

EVF: early vertical forearm basically aims to position your forearm as close to vertical as early as possible - as determined by Newton's Third Law: until you are pushing backwards with your forearm, there is no forward propulsion generated from your arms. It is the new way of explaining high elbow. The larger the surface area and greater the force pushing backwards on the water, the more forward propulsion there will be.

Kayaking: Popov's method of swimming, simply put, is continuous swimming (avoiding dead spots by unnecessary gliding). Imagine doing a front crawl arm motion while holding a broom handle, with one hand at each end of the pole. Alexander Popov who was coached by Gennadi Touretski was known as one of most efficient front crawl athletes in the world at the time he was competing. He had a relaxed smooth style, which gave the impression he was gliding. He was actually using the kayaking method where one arm is always pushing the water backwards, so he never lost his forward momentum.

SUMMARY POINTS

Take up as little shape as possible in the water, try not to present blunt shapes pushing forwards against the water and instead try to make them as streamlined as possible. Keep any action that is not pushing backwards to create forward propulsion as relaxed and smooth as possible, allowing you to use most of your energy in moving you forwards as efficiently as you can.

Remember to focus on hydrodynamics (body position) to reduce drag as well as Newton's law of action and reaction, push backwards to go forwards.

1Ernest W. Maglischo, Swimming Fastest. (Champaign,...