To win swimming gold in Tokyo, swimmers not solely must generate unbelievable energy with their legs and arms to propel themselves by way of the water; in addition they have to beat the relentless pull of the water’s drag whereas doing so.
With out having the ability to don particular low-drag fits or use applied sciences to assist them fly over the water, how can swimmers make the impact of the water’s drag as small as potential?
The perfect athletes on this yr’s Olympics will do it by swimming below, somewhat than on high of, the water – at the least so far as the foundations enable.
‘Quick fits’ and Olympic swimming: a story of decreased drag and damaged data
Waves are a drag
Water is way denser than air, so that you would possibly assume swimmers would profit from utilizing a method that permits them to sit down excessive within the water, with as a lot of their physique out of the water as potential.
However there are two issues with this technique.
First, it prices power to supply the forces wanted to elevate the physique, which might be higher spent propelling the swimmer forwards in direction of the ending wall.
Second, once we journey on the water’s floor we waste power making waves. Throughout quick swimming, comparable to within the dash freestyle occasions or throughout begins and turns (the place speeds exceed 2 metres per second, or about 7 kilometres per hour), wave era slows the swimmer down greater than some other issue. Lowering wave formation is subsequently important to swimming success.
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Waves are produced because the strain exerted by the swimmer on the water forces the water upwards and out of their path. Different strain adjustments across the swimmer’s physique additionally trigger waves to type behind them, and typically to the facet.
The power required to generate waves comes from the swimmer themselves, so a whole lot of the facility generated by the swimmer’s muscle tissue is utilized in wave era somewhat than transferring the swimmer forwards.
However waves aren’t fashioned once we (or fish, dolphins or whales) swim below the water, as a result of waves solely type when an object (like us) strikes on the boundary between two fluids of various densities, comparable to water and air throughout swimming. And this reality hints at an intriguing answer to the drag difficulty.
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A change in considering
Swimmers had observed the advantages of staying underwater from at the least the Nineteen Fifties.
The breaststroke occasion was the reason for main controversy within the 1956 Melbourne Olympic Video games as swimmers experimented with staying underwater for a lot of their races. The winner of the lads’s 200-metre occasion, Masaru Furukawa of Japan, swam underwater for a lot of the first three laps of the four-lap race. This observe was swiftly outlawed after the video games; swimmers have been pressured to floor earlier than they may begin to swim.
However the observe of swimming underwater in freestyle (entrance crawl), butterfly and backstroke occasions solely took off after swimmers mastered the “underwater undulatory method”, higher referred to as the dolphin kick.
Right here, the swimmer propels themselves underwater by undulating the decrease physique in a wave-like method whereas sustaining a inflexible and streamlined higher physique place with arms stretched overhead.
The amplitude of the decrease physique undulation will increase from the hips to the ft so the “wave” produced by the physique is way larger down in direction of the ft, making a whip-like impact. This pushes water quickly backwards, propelling the swimmer forwards in line with Newton’s legislation of motion and response.
Utilizing this method, swimmers within the backstroke occasions gained a major benefit from the Eighties onwards, and from the Nineteen Nineties it was additionally widespread in freestyle and butterfly occasions.
The method was so efficient that swimming’s governing physique, FINA, restricted its use to solely the 15-metre section after begins and turns. Swimmers at the moment are disqualified in the event that they swim too far underwater.
But the advantages of bettering the underwater undulation method are so nice that swimmers nonetheless spend hours every week in coaching bettering this a part of the race.
Keys to underwater swimming success
Though an ongoing analysis effort goals to seek out the optimum method for various swimmers, a couple of practices appear to be generally related to underwater success.
First, swimmers who keep underwater for the complete 15 metres may have sooner begins, turns and total race occasions. This impact is especially robust in backstroke occasions, and when swimmers benefit from the ultimate flip in a race (when swimmers normally floor faster as a result of they’re rising drained).
Second, staying deeper underwater is necessary. Wave drag is barely decreased by swimming just under the floor, however swimming 40–60 centimetres underwater can scale back drag by 10–20%. And there are additional advantages when swimming a metre or extra below the water, particularly when begin and switch push-off speeds are quick (as in most shorter races).
Third, one of the best swimmers will doubtless show a sooner kick frequency, though every kick is not any greater than these of slower swimmers. Particularly, a quick extension of the knee within the downbeat of the kick that happens on the finish of the wave-like movement could separate the sooner from slower underwater swimmers.
And eventually, though it will likely be laborious to identify within the underwater digital camera pictures on the Olympics, the ft of the sooner underwater swimmers could rotate inwards through the downbeat of the kick, somewhat than staying rigidly in keeping with the leg. This rotation permits the highest surfaces of the ft to orient horizontally to the swimming course, similar to the flute (tail) of a dolphin or whale lies horizontal to their swim course, producing extra propulsion on the ft.
Submarining in direction of gold
So, on the Tokyo Olympic Video games, search for the swimmers who keep underwater so long as allowed in begins and turns, and verify the methods they use when the director cuts to the underwater pictures.
The swimmers who benefit from these components of the race would possibly simply propel themselves to Olympic gold.