Some science of swimming

This piece is an extract from the Torpo website User Training Guide which gives some background

on swimming science and some basic guidance on how to use Torpo. I’ll cover the training and use

in a further blog post. I strongly recommend the book Swimming Science by the great Dr. G John Mullen and follow ‘thesocialkickpodcast’ on Instagram.

Understanding and controlling the fluid dynamics of swimming is essential to earning a spot on the medal stand

The understanding of Hydrodynamics isn’t high on the list of interests of most swimmers, despite being keen to improve. Yet such a theoretical and hence practical understanding of how water acts on the swimmer's body will give far larger gains than just repetitive training. Though there are aerobic and anaerobic benefits of quantity training in swimming, for increased speed over short and long distances, the swimmer must improve technique in order to see significant gains. To have better technique, swimmers should employ training methods that increase efficiency in the water. Such efficiency is largely about reducing drag and maximising output from every effort expended.

A theoretical and hence practical understanding of how water acts on the swimmer's body will give far larger gains than just repetitive training.

Diagram showing how drag varies depending upon the shape of the object facing the water

As you see from this diagram, ‘form’ (or

frontal) drag varies depending upon the shape of the object facing the water.

And consider this equation about drag: Fd=1/2⍴V²ACd where:

Fd=Drag (form) Force on a swimmer

=water density

V=velocity of a swimmer’s body

A=frontal area of a swimmer’s body

Cd=coefficient of drag

So, simply, because you cannot change the density of the water whilst you’re in it, or the shape of your body, you can only change the speed that you swim and the area and shape of your body which is presented to the water. Hence you can kick and pull the water with your arms harder to swim faster. But you can also reduce your frontal area (A) facing the water and streamline your shape (Cd).

From this you can deduce the lower the drag coefficient (the better the technique), the higher the velocity. Note how a streamlined shape like Torpo has the lowest drag coefficient of all the shapes shown here. This helps it as a training aid, but it also shows you the importance of streamlined body shape in reducing drag on the swimmer. The in the formula shows that drag increases by the square of the swimmers' speed, or more simply, the faster you swim the more important it is to reduce your frontal area and be streamlined to reduce drag. *(For more information on this subject and the scientific study of swimming, we recommend the book ‘Swimming Science’ edited by G. John Mullen).

Good quality teaching and coaching are fundamental to reducing drag; as is repetitive guided training. Use of a variety of aids can also help the swimmer by developing a better (horizontal) body position, becoming more streamlined, reducing frontal area, and to gain a ‘feel’ for drag created by the water. Pool swimmers generally swim the range of strokes, whereas triathletes and open-water long distance swimmers predominantly focus on front crawl/freestyle. Yet all swimming benefits from improved technique, be it raw speed for pool sprinters or stroke efficiency for longer distance swimmers and triathletes.

Good quality teaching and coaching is fundamental to reducing drag; as is repetitive guided training.

Body rotation and kick in any freestyle swimming is crucial to both efficiency and speed. Whereas the modern sprinters have developed a flatter stroke, the kick is crucial to the speed and the body must control the rotation of the arms and the shoulders. This stroke is not efficient over a longer distance because it creates more drag. Yet power overcomes this at the margin in order to improve speed over a short distance. In longer freestyle events, body rotation and streamlining are vital to the efficiency of the stroke and hence speed over a longer distance. And to improve rotation, the body must move as one from the control of the head down to the feet. So, for triathletes and long distance swimmers, the kick may be more to flatten the body position, hence reducing drag. It will also help body rotation to lengthen the stroke (increasing distance covered per stroke) and presenting a lower torso frontal area as the upper body and shoulders rotate (again reducing drag).

The four forces; thrust, lift, drag and mass are shown on a lady swimming in the pool
Forces on a swimmer

So, the freestyle kick should not be solely downwards, especially in longer distance swimmers. Generations of swimmers have learned with ‘flat’ kickboards, developed in the 1940s, which inherently stop rotation. Such flat kickboards are important for young and inexperienced swimmers, giving balance whilst they learn to kick. Yet as swimmers develop, this balance or stability becomes a hindrance when developing the rotation which is vital in an efficient stroke. There is now a training aid that encourages rotation, in addition to helping improve core strength and having a low drag coefficient which allows use in all strokes. This is Torpo®.

Why Torpo works

Torpo works by being perfectly unstable in the rolling motion side-to-side like a ‘Swiss Ball’ is in the gym. It allows swimmers both inexperienced and highly competent to roll whilst kicking as in a front crawl stroke. It will help young swimmers to roll more freely and develop a better leg kick and body motion as they improve their swimming. Rotating to 45-60 degrees is easy with Torpo, helping swimmers learn the correct body roll angle by mental and muscle memory whilst training with Torpo. So, when the full stroke is performed, a more accurate and natural body roll ensues. It can also help the advanced swimmer, opposing hip roll which balances the swimmer whilst rolling the upper body.

Like a Swiss Ball, it will also help develop greater core strength as the swimmer has to control the unstable rolling motion with core muscle strength. This appears subtle at first when using Torpo, although more pronounced with greater use. Even an Elite swimmer could feel the benefit to the core on initial use.

Woman uses a gym swiss ball to destabalise her legs whilst performing hip thrusts

The idea for Torpo was inspired by the way modern fighter jet aircraft are designed. These aircraft are designed to be ‘unstable’, allowing fast roll rates whilst controlled by computers with small ‘canard’ flight control surfaces.

A Typhoon jet aircraft showing the computer-controlled canard flight control surface

Similarly, Torpo is designed to be unstable so the swimmer controls roll during front crawl kicking drills, as would be done during the full stroke. In front crawl swimming, this enhances hip and shoulder rotation, minimising drag and improving speed. It means kicking drills teach correct body movement from a young age up to elite levels.

A Typoon jet aircraft in flight showing rapid roll rate

Rapid roll rate is important in modern fighter jet aircraft. This is achieved by aircraft instability, which canard flight control surfaces controlled by computers.

This is important in freestyle swimming because body rotation is crucial to reduce drag. So natural sideways instability, with hands and feet as the control surfaces, helps improve the rotation. Swimmers can develop accurate and coordinated body rotation, controlled mostly by hand movement, through a series of training drills. These drills focus on instability and rotation.

There are many muscle groups that benefit from Torpo’s instability. In the side of the body, these include the latissimus dorsi and the serratus anterior. In the back from the pelvis up to the neck, the erector spinae, there are three groups of controlling muscle. In the neck and shoulder area are the deltoid and trapezius muscles. In the stomach, the rectus abdominis and abdominal oblique external muscles work to control body roll and core strength. And in the chest, the pectoralis major are controlling the arm movements.

The natural teardrop design of Torpo reduces drag significantly against a flat kickboard. It allows greater streamlining, hence more speed whilst kicking. This then enhances the effect of the kick closer to the kick whilst swimming front crawl. Though if increased resistance is required for the kicking drill, Torpo can be held vertically which will produce drag akin to a ball.

The natural teardrop design of Torpo reduces drag significantly against a flat kickboard. It allows greater streamlining, hence more speed whilst kicking.

Shoulder impingement and lower back pain are frequent in regular competitive swimmers, especially when kick-training over large distances. Torpo encourages ‘head down’ kicking with side breathing, as would be done in the front crawl stroke. Whereas the flat kickboard is often used as chat time with head up, Torpo will force swimmers to maximise their drills. The flat kickboard is mostly inclined causing significant drag. This also places a lift on the board forcing the arms and shoulders up. Whilst Torpo may not entirely solve these issues, the biomechanics of Torpo with improved arm and head position may reduce strain on the

the rotator cuff in the shoulder and the lumbar spinal area and related muscle groups.


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