How science can help us swim faster

Water seems to exist beyond the sphere of logical science sometimes. You know the days – the ones where you get into the pool or lake and it feels like someone has tipped treacle in. Every stroke is an effort, you’re fatigued after a few hundred metres and would swear someone has attached bricks
to your feet.

Then there are the good days – the days you feel more dolphin than human, slipping though the water with ease, wondering why it can’t be like this all the time.

Obviously the water is the same though (provided you’re in the same conditions) so why does it feel so much harder some days – and what can actually help to make us faster?

Density and drag

First, it’s worth briefly considering the properties of water. Without going too into GCSE chemistry, water is the only abundant substance on earth to exist as a gas, liquid and solid and each molecule is made up of one water and two hydrogen atoms.

Water’s density is 1 gram per cubic centimetre, which is around 800 times that of air, and the hydrogen bonds also create surface tension (which is why light insects can sit on the surface).

So if you’ve ever thought swimming is much harder than cycling or running – you’d be right – and this helps explain why swimming is so much harder on days you’re tired or a bit under par.

So what does this mean for us as swimmers? Here to simplify things is Paul Newsome, head coach and founder of swim coaching platform Swim Smooth.

“We know that water is 800 times more dense than air. So consequently the resistance that you encounter when you’re swimming is much, much greater.

“That creates drag which slows us down – so basically when we try to swim, we are looking to minimise drag and increase effective propulsion. For most new swimmers, reducing drag is the key thing.”

Professor Huub Toussaint, holder of a PHD in Swimming and Professor of Human Movement Science in the Academy for Physical Education and Associated Professor of Biomechanics at the Free University in Amsterdam, Netherlands – as well as namesake of the Derby-based wetsuit brand – explains in a little more detail.

“The primary factors influencing swim speed are mechanics and energetics. Swimming fast requires generating enough propulsion to overcome the drag forces that impede forward motion.

Technique plays a crucial role, as effective propulsive actions result in high forward-directed forces while minimising excessive bodily movements that increase drag. Streamlining is also essential to maintain low total drag forces. Unlike propulsion on land, swimming involves a moving propulsion point.”

Unluckily for us as humans, we aren’t exactly designed to be fast swimmers. Think of some familiar aquatic creatures – for example seals, dolphins, fish – and you can see they’re all streamlined, muscular and efficient in the water.

Compare that to humans, who have a less streamlined shape and long limbs flapping about and you can start to see where the problems occur. What both Newsome and Toussaint are getting at here is that we want to be as propulsive as possible (generating forward movement) but without losing that to drag.

“Yes, this introduces the concept of energetics, as energy is lost to the aquatic environment during the propulsion process,” says Toussaint. “Good swimmers excel at generating high propulsion, minimising drag, and minimising energy loss.”

Swim technique

Of course, there are some differences in water that affect our swimming. Pool swimmers will talk about ‘fast’ and ‘slow’ pools, where elements such as depth, the distance between the pool edge and the water level, and the type of lane ropes can affect times.

In open water there are even more – as salt water adds buoyancy, currents, waves and tides affect us (plus we tend to swim on the surface so are more at the mercy of conditions, rather than animals which will be under the water).

How can our swim technique can improve our speed?

Paul Newsome identifies some key elements that can help or hinder. Swim Smooth advises working on your breathing first as a new swimmer (or swimmer looking to improve) but once that’s nailed, it’s all about reducing drag.

“Looking too far forwards, lifting your head too high, and having crossovers in your stroke – which cause scissoring of the legs – creates additional drag. Having stiff ankles and tight hip flexors will also create drag at the back of the stroke, as the legs sit down a lot lower than they should.”

When we think of the body in its entirety, our goal is to be as streamlined as possible.

Swim Smooth recommends bilateral breathing (the ability to breathe to either side, either every three strokes or alternating between each side depending on conditions, or mixing it up depending on the swim) as a way of creating more balanced rotation in the body.

From there, it’s about getting the body as horizontal as we can, rotating in the water within the smallest area possible (some swimmers find it helpful to imagine swimming in a tunnel or tube!).

As we can see, these common faults and the methods to correct them centre on creating a high, horizontal body position where the body rotates evenly and with good control – and that’s even before we bring in the propulsion created by using our arms and kick.

Wetsuits and swimskins

All of this is a rather long-winded way of saying once we understand how water behaves (it’s very dense and hard work!) and how our swim technique needs to work efficiently to help us move through that density (effective propulsion minus drag).

Where it gets interesting for some triathletes though, is in one key thing – yes, it’s time to talk wetsuits.

Go to any big triathlon and the pre-race chat is always around water temperatures and (in the height of summer) if there’s a chance they’ll be banned as the water is too warm.

It’s no surprise either, as developments in wetsuit technology have meant that the suits we have access to these days do so much more than keep us warm – they give us buoyancy, make us more hydrodynamic and can even help correct flaws in our swimming.

So if you’re a weaker swimmer, chances are you’ll be much quicker once you pull on the neoprene.
When it comes to swim technology, though, the sport is way behind the investment we’ve seen in bike speed and aerodynamics.

Look at the time and money spent by cycling teams and manufacturers in wind tunnels versus the lack of equivalent technology in swimming, and you can start to see that perhaps we are only in the early days of advancing our performance through the kit we use when we try to achieve speed in water.

In the meantime, Professor Toussaint has been instrumental in looking at in-water wetsuit testing alongside Huub Design, with the invention of their unique ‘M.A.D. system’:

“To gain a deeper understanding of swimming, we developed the Measure Active Drag (M.A.D.) system,” says Toussaint.

“It involves a long ladder mounted under the water, providing fixed push-off points for swimmers. These points are instrumented to measure forces. At a constant swimming speed, average propulsion is equal to average drag.

“By using the M.A.D. system, we can determine a drag profile for a swimmer and compare it across different suits. For instance, some swimmers may experience increased drag due to sinking legs.

“We can quantify the amount of buoyancy needed to offset the added drag from sinking legs. This system allows us to measure the drag reduction and performance improvements such as added compression, buoyancy, or the effect of an exoskeleton.”

Developing the system was important to Huub founder Dean Jackson.

“I’ve always been frustrated when people don’t talk honestly about their level of research. But unfortunately, there’s no really good measurement, or a wind tunnel for wetsuits out there, so Professor Toussaint and I decided to build the very best piece of equipment to measure drag on water for swimmers.

“Putting it bluntly, we test when others simply don’t. Our level of understanding is so advanced — and it’s a position we intend to hold.”

Working with the Professor, Jackson next bought in Paul Newsome to advise on common swim types.

From there came the development of the 3:5 and 3:3 buoyancy profiles, based on how much lift a swimmer needed in their lower body (the 5mm in the legs giving more lift for sinky swimmers), as well as the ‘exoskeleton’ designed to give more core stability and prevent snaking.

Top-end swim speed

Nowhere is it more important to maximise speed in water than in pro racing, though – something which three-time Olympic medallist Jonny Brownlee is well aware of [see above for more from Jonny].

After all, while their swim time may not make or break a race, missing out on that early swim exit is crucial to making the lead bike pack and that really is where magic (or disaster!) can happen.

“I started to swim very, very young. So I’m one of those fortunate people in that I’ve always had that swimming stroke,” says Brownlee.

“But obviously when you compete, you’re always thinking about how you can move faster. My philosophy on swimming is simple. Really, it is – you keep your hips high and then you try and get the best possible pull on the water you can.

“I think what a lot of people do wrong is they either rush a stroke, or don’t grab the water to the front and then push out the back. As triathletes sometimes, because we’re fit, we can end up throwing our arms over too quick and not actually pulling water.”

Despite one of the best strokes in the business, the marginal gains offered by kit are still important, though, and resulted in both Jonny and brother Alistair Brownlee working with Huub on the development of the suit they both race in – the Brownlee Agilis.

“We want to make sure we’re wearing the fastest kit. You know, we do all the training we do to prepare as well as we can. And my philosophy is you want to be on start line knowing you’ve got the fastest kit too,” says Jonny.

“So the guys at Huub were working with us on that. We took the design back to making it as flexible as possible on the arms and then as much buoyancy as you can around the waist. Where the panels were stitched or glued made a huge difference too, as you take some flexibility away in those areas.

“Usually when you put a wetsuit on you feel a bit restricted,” continues Jonny. “But as soon as I put on the finished Brownlee suit I felt I could swim 5 or 6 km straight away so I knew we had created a good one”.

Not all pro swims are wetsuit ones though, in which case athletes may opt for a swimskin. Working slightly different to a wetsuit, a swim skin is designed to be as tight and compressive and streamlined as possible.

More marginal gains?

So from body mechanics to wetsuits designed with science and marginal gains in mind, we can see there’s a lot that can help you swim faster. But what about the future?

The feeling in many quarters is that we’re still only beginning to explore swim speed and especially swim speed in open water (after all, who can forget the ‘technical doping’ drama as FINA banned certain swimsuits in the early 2000s?).

Beyond wetsuits and swimskins though, we can look at other apparel – for example swim caps are often race-issued in triathlon and not as streamlined as they could be or designed to maximise hydrodynamics.

This in itself is more complex than, say, an aero helmet on the bike, as our head moves as we swim. The same goes for goggles. While there is a lot to be said for choosing a set that are comfortable and give great visibility for age-groupers, could the pros maximise speed more in their choice of a sleeker or lower-profile goggle?

Admittedly, for the average age-grouper these are small concerns in the big (watery) picture. The best advice? Work on your swim technique as much as you can to reduce drag – coaching can give huge benefits – and make sure that you are not too reliant on your wetsuit to get round your chosen triathlon swim distance.

As for a wetsuit, think about your technique when choosing a suit and get the one that fits you the best and supports your swimming.

For the average swimmer a bit of buoyancy in the legs, some core stabilisation and flexibility in the arms can work wonders – until at least, some kit is invented that really can make us swim like dolphins…

All images credit: Huub Design