Most swimsuits are made of different combinations of spandex, polester and nylon. Recent research and development done by the Speedo company has produced swimsuit material that is water resistant and extra tight. The Fastskin II, or FSII, is a line of swimsuits made of Speedo's patented Fastskin fabric, designed to react to water the same way that sharkskin does: it repels water and reduces drag.
In order to develop the FSII fabric Speedo scientists studied sharkskin. Sharkskin, laden with millions of small, V-shaped skin ridges called dermal dentricles, is a hydrodynamic casing of sorts. These dentricles allow water to pass over and around a shark's body very efficiently, reducing drag. This drag-reducing power is what Speedo sought when it designed the FSII with tiny ridges that emulate sharkskin.
Tighter Means Less Drag
The FSII fits onto the body very tightly. Speedo used digital scans of swimmers in eight different body positions in order to design a suit that fits properly on a body engaged in rigorous physical activity. The result was a three-dimensional swimsuit design. The FSII will fit very tightly when worn properly, but will also stretch comfortably along with you. The tightness of the suit prevents the suit (and skin) from oscillating in the water and thereby creating drag.
FSII Bodysuits are Gender-Specific
Speedo also studied the general differences in the way male and female swimmers are shaped and applied the results to the production of their FSII bodysuits.
Male FSII bodysuits feature the Fastskin fabric in all panels except the underarm panels, which are made of "Flexskin," and allow full range of motion.
Female FSII bodysuits feature Flexskin fabric as well as the Fastskin fabric, but on the female suit the Flexskin is located on the side panels, for a wrinkle-free and drag-reducing fit.
FSII Behaves like Tendon and Muscle
The panels of Fastskin or Flexskin in the FSII behave much like muscles, stretching and returning to their original positions as the swimmer swims. The seams behave as tendons do, providing tension in the suit. The seams allow the fabric to be stretched to its maximum, which offers the swimmer total freedom of movement, something seemingly unimaginable in such a tight suit. Because the seams need to be sewn in very tightly, fifty-two inches of thread go into every inch of seam!
By testing swimmers in different suits over different two hour workout periods, Speedo was able to determine that the Fastskin fabric has three per cent less surface resistance than their previous high-tech suit: the Aquablade.
Speedo also determined that the full-bodysuit (FSII with arms) is 7.5 per cent faster than all of the other suits used in the study.