Why is lycra used for sportswear?

Answer 1

Several reasons.

The compression of the fabric, slightly reduces muscle vibrations, leading to enhanced performance.

The wind resistance is reduced. Without the other factors a naked shaved body would have least drag through the air, but in some cases the actual fabric itself can be engineering to be less drag than this ideal. Imagine a flag, flapping in the wind, well you don't want clothes that are like a flag.

It reduces friction, between body parts, legs, armpits, etc and moves with the body instead of moving over and chaffing the body. This can be a problem for sensitive parts of the body eg, nipples.

It provides cooling for the body, the close fitting thin fabric helps wick the sweat, the body's cooling mechanism away from the body, enhancing the cooling effect. Of course there can also be incorporated panels of thicker or lined Lycra to keep warm as necessary.

It stretches and is lightweight. Think about it, try bending over into the starting blocks of a sprint race wearing nomal jeans (without Lycra) and a cotton button up shirt. Then imagine how much easier it would be without the heavy restrictive clothing, that probably prevents you actually getting into that position without hoisting you waistband, or shuffling your shirt around your shoulders.

Basically it is the most practical, comfortable material, and looks good too, superman, power girl, Spider-Man all the superheroes.