Most technical fabrics are labelled to wash on cold, because the high pH of most detergents can damage synthetic fibers.  That's especially true of stretchy fibers like spandex.  But WIN is one of the only low pH detergents on the market, so you're not limited to cold water.
Washing with warm or hot water uses more energy, so if you can get your clothes clean with cold then stick with it!  But anyone who has ever washed a frying pan knows that warm or hot water removes oils and other residues better than cold water, so if you want to get your clothing truly clean and like new, try WIN with hot water.