Here is an Apple Watch accessory that lets you exercise with your smartwatch more comfortably. The Twelve South ActionBand for Apple Watch has soft, flexible terry cotton bands that absorb sweat on your wrist. It also protects your Apple Watch band. It is designed to work with Apple Watch Series 4, 5, 6 & SE.
The ActionBand for Apple Watch gives you full access to the Digital Crown and Side button. The above video shows what you get. More information is available here.