Shape-retaining swimwear for fitness training.Shape-retaining swimwear for fitness training. The sporty-look Muscleback features an eye-catching orange and yellow chevron panel design inspired by our medal-winning Fastskin collection. The muscleback style offers flexibility during your swim and includes a medium neck and a modest back opening so you feel confident and secure. Soft and stretchy, our Endurance10 fabric contains Creora HighClo for a fit that stays like new for longer.