
What you wear to your fitness class depends largely on comfort. While there are no hard and fast wardrobe rules, here are some things to consider:
Temperature. There is a good chance you will sweat in aerobic classes, so be sure to choose clothing that breathes and keeps you comfortable. If you know you get hot easily, choose shorts over workout pants. If you're exercising outdoors, dress in layers to deal with cooler weather.
Sweat. If you sweat a lot, you might want to consider choosing darker clothes that don't show moisture as much, or different materials that dry more quickly.
Aerobic and Weight Training Classes. Good shoes are key. Make sure your clothes allow you to move freely.
Mind/Body Classes. Since you never know if you're going to be upside-down or have your legs in the air, it's a good idea to wear pants rather than shorts to avoid self-consciousness. Baggy clothes could shift and expose skin you were intending to keep under cover, and they hide the specifics of the position of your body. Not only will body-hugging clothes keep you covered, they allow your instructor to take note of your alignment and assist you in finding a safer or more precise position.
Most mind/body classes are performed barefoot. While socks tend to be too slippery for yoga, they can usually be worn in Pilates and during some of the yoga poses. It's fine to take a pair with you in case your feet get cold.
These classes often end with a rest period (called savasana in yoga) in which you sit or lie quietly for a few minutes. It's a good idea to bring a blanket or sweatshirt with you to use during this time, since it is hard to relax when you're cold.
Appropriateness. There is such a thing as too short. It's your workout, and your comfort comes first -- but keep your classmates in mind when choosing your gear.