One study found that performing static stretches before doing a barbell squat caused people to feel off-balance and lift less weight, while another showed that soccer players who did static stretches before a 30-meter sprint had slower times than players who didn't stretch before the sprints. Finally, a meta-analysis of 104 studies concluded that static stretching had negative effects on strength, power, and explosive performance, and should be avoided altogether.
Another bummer: Some research suggests that stretching won't do much to eliminate muscle soreness. In a review of 12 studies, researchers found that pre- or post-exercise stretching didn't stop bothersome aches and pain. (The likely reason: Micro-tears in the muscle and surrounding connective tissue are to blame for soreness, which stretching won't repair.)
More from Greatist: Why Are Your Muscles Sore After a Workout?
The Bottom Line
Your best bet: Do some dynamic stretches before a workout, which can prepare your muscles and even improve athletic performance. With all the evidence against it, it's probably smart to avoid static stretches before a workout.
Still, Mulcahy believes static stretches can be helpful for people who spend a lot of time sitting at a desk. She suggests loosening up hamstrings, hip flexors, shoulders, and back muscles with static stretches (post-workout) a few times a week. In the end, be sure to talk to a certified trainer to find a plan that best suits your fitness level and goals.