"Whether I take my workouts outside or do them in my chilly apartment, a long-sleeved shirt I can work out in is a must. I've been loving the Lululemon Swiftly Tech Long Sleeve 2.0 Shirt ($78) the brand sent me for my winter workouts. I like that it's more loose-fitting, but it still feels fitted enough to stick to you while you work out. Plus, it's not too warm, and my skin can still breathe when I get sweaty. Another bonus? If I do a lunchtime workout, it looks chic enough to wear on a work video call afterward." — CS