(This is the third in a series of stories about the science
behind the Olympics to run daily this week. The full list will
be updated at )
By Sharon Begley
NEW YORK, July 17 The sharkskin has been
retired. The swim bladder, too. For London's Olympic swimmers,
the watchword is more "barracuda".
Swimsuit makers have long sought inspiration in the oceans,
where evolution spent about 500 million years sculpting bodies
shaped to cut through the water with the least drag or studded
with features that increase speed. That led some manufacturers
earlier this decade to develop full-body, impermeable suits:
water could not get in and air could not get out, trapping air
inside and increasing buoyancy much as fish's swim bladders do.
Water offers greater resistance than air, so swimmers whose
bodies rise higher in the water have an advantage. That led
international swimming federation FINA to outlaw full-body,
impermeable suits in 2009.
The other innovation of the last decade was Speedo
International's sharkskin-inspired suits. Called Fastskin and
introduced in 2000 for the Sydney Olympics, the suit was studded
with tiny hydrofoils with V-shaped ridges like the "dermal
denticles" on sharkskin. It seemed to be a success: 83 percent
of swimming medals at Sydney went to athletes wearing Fastskin.
That was not quite slam-dunk evidence of its superiority.
Speedo, owned by the Pentland Group, had reached out to the very
top competitors to wear its suits in the first place.
In March, researchers at Harvard University published an
analysis of Fastskin and real shark skin in the Journal of
Experimental Biology. They found that although real shark skin
was 12 percent faster with denticles than without, Speedo's
fabric was not. It was actually faster inside out than with the
denticles exposed to the water.
By the time the study appeared, Speedo was already years
into research on Fastskin's successor. Called Fastskin3 and
first used in competition this year, it includes caps, goggles
and suits that redistribute water flow around a swimmer to
decrease drag, partly by compressing the body's silhouette along
the lines of the predatory barracuda.
"We operated on the principle of minimal gains," said Joe
Santry, research manager for the company's Aqualab. Rather than
getting a huge increase in performance from a single design
change, Speedo's scientists squeezed a few percentage points of
improvement from many individual modifications. The fruit of
their efforts will be on display next week at the London Olympic
THE PERFECT BODY
They started at the top. "The cap and goggles are the first
things that hit the water, so they can create turbulence
downstream in a way that affects the performance of the suit,"
The scientists scanned athletes to produce a
three-dimensional, digital avatar. They then manipulated various
parts of it - squeezing here, filling in there - and used
computational fluid dynamics to calculate how each change
altered drag "until we found a theoretically perfect body form."
Take the cap. The standard model is a plain silicone bowl
that wrinkles at the top. Those wrinkles, like any protuberance,
create drag. But shaping a cap to the average human head shape -
determined by the 3D head-scanning - minimizes wrinkles.
The new cap also has room to pack hair at the nape. That
fills what is otherwise a dip between the head and the back.
"That dip creates a pressure drag," explained Santry: a region
of lower pressure that ever-so-slightly sucks the swimmer
backward. Packing the hair into the gap decreases that drag 3.4
percent compared to standard silicone caps.
The most hydrodynamic goggles shape - a full-face mask
reminiscent of Batman's - violates FINA rules. But the runner-up
takes the water flowing over the head to the eye sockets and
basically attaches that flow to the face, creating an
ultra-smooth "boundary layer" of water.
Smoothness is key. Boundary layers naturally flow toward
regions of low pressure, which can split up the layers and
create turbulence, increasing drag. The optimal goggle design is
shaped like a water droplet and turned up at the temples. "It's
unlike anything on the market," said Santry.
The goggles cut drag 2.2 percent versus other Speedo models.
The suit redesign addressed the fact that 80 percent of the
drag on swimmers comes from their shape. That meant compressing
fleshy areas like the thighs, rear end and, for women, the
chest, all with Lycra panels sewn into the suit.
While other suits absorb water, Fastskin3 repels it. Less
weight from the suit means each stroke propels a swimmer
farther. So after four years and 55,000 hours of research and
testing, the complete outfit reduces drag by 16.6 percent
compared to standard gear, Speedo says.
That translates into an approximately .11 percent potential
increase in speed. Not huge, but then the difference between
winning gold and silver can be thousandths of a second. At
Beijing, American Michael Phelps finished 0.01 second ahead of
Serbia's Milorad Cavic in the 100 meter butterfly. Phelps will
be wearing Fastskin3, as will team mate Tyler Clary and
Britain's Rebecca Adlington.
"The recent suits work," said kinesiologist Joel Stager of
Indiana University, who has studied the science behind swimming
for decades. "The earlier ones (with denticles) didn't."
As it happens, compressing swimmers' bodies has a benefit
besides reducing drag: it also increases blood flow. Think of it
as a legal version of blood doping.
(Editing by Michele Gershberg)