The short answer is both, but in different ways. Before your workout, dynamic stretching and movement-based warm-up exercises are recommended to increase blood flow, raise your core temperature, and prepare your joints and muscles for the demands of training. Static stretching, where you hold a stretch for an extended period, is best saved for after your session when your muscles are warm and pliable, and it is effective for improving flexibility and reducing post-workout tension. Skipping your warm-up entirely is one of the most common contributors to unnecessary injury, so even five to ten minutes of intentional preparation before training makes a meaningful difference in both how you perform and how you feel afterward.