Don’t let your days off be a time to slack off. Use the extra hours to put in time outdoors with a serious workout. During the week, we often feel a bit constrained—fitting in efficient workouts before the day gets going. But on the weekends, after sleeping in and fueling up with a big breakfast, you can enjoy the fresh air and really get into your fitness time. Here's what we're wearing these days, from Nike's new trainers and some ultra-comfortable track pants to a pair of sunglasses that are surprisingly durable and shockingly affordable.