For some, stretching in addition to a workout seems like the cherry on top of a sundae—a nice touch, but not necessary. Or maybe you think that touching your toes for a few seconds after a treadmill session is plenty. Turns out when (and how) you stretch your muscles can make or break your fitness goals.

Get Moving

Stretching before a workout is crucial for preventing injury as well as improving performance. Especially if you exercise right after waking up or if you’re pretty sedentary during the day, your muscles are going to be tight, says Noam Tamir, certified trainer and founder of TS Fitness. One study showed that stretching 15 minutes before a workout can help you avoid injury.Warm-up and stretching in the prevention of muscular injury. Woods K, Bishop P, Jones E. Sports Medicine (Auckland, N.Z.), 2008, Mar.;37(12):0112-1642.

So what kind of moves are we talking about? “It’s best to do a dynamic warm-up before exercise,” Tamir says. As opposed to static stretches, which are held for 30 seconds or more in the same position (think toe touches), this type of stretching involves active movements that mimic your actual workout. For example, runners often perform dynamic stretches like hip circles, walking lunges, and butt kicks to activate the muscle groups used in running. During dynamic stretching, you’re constantly moving, so it provides a cardio warm-up as well, explains Julie Mulcahy, M.P.T., a sports medicine physical therapist.

Not only will you reduce your risk of injury, but research also shows that dynamic stretching can help improve athletic performance. One study found that college wrestlers who completed a dynamic warm-up for four weeks saw improvements in strength, endurance, agility, and anaerboic capacity.Four-week dynamic stretching warm-up intervention elicits longer-term performance benefits. Herman SL, Smith DT. Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2008, Sep.;22(4):1533-4287. Other research suggests that dynamic stretching enhances muscle performance and power output compared to static stretching.Acute effects of dynamic stretching, static stretching, and light aerobic activity on muscular performance in women. Curry BS, Chengkalath D, Crouch GJ. Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2009, Dec.;23(6):1533-4287.

The Problem With Holding Tight

Because the thought of doing a mini-workout before your actual workout sounds exhausting, many of us instead resort to a few half-hearted toe tugs after exercise. Static stretches like these focus more on relaxing the muscle and promoting flexibility than dynamic stretching, Tamir says, and can be good to add to the end of your gym session.

However, recent research has questioned the benefits of static stretching before a workout, suggesting it may lead to decreased athletic performance. 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.Acute effect of passive static stretching on lower-body strength in moderately trained men. Gergley JC. Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2013, Dec.;27(4):1533-4287. The effect of static stretching on phases of sprint performance in elite soccer players. Sayers AL, Farley RS, Fuller DK. Journal of Strength and Conditioning Research / National Strength & Conditioning Association, 2009, Feb.;22(5):1533-4287.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.Does pre-exercise static stretching inhibit maximal muscular performance? A meta-analytical review. Simic L, Sarabon N, Markovic G. Scandinavian Journal of Medicine & Science in Sports, 2012, Feb.;23(2):1600-0838.

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.Stretching to prevent or reduce muscle soreness after exercise. Herbert RD, de Noronha M, Kamper SJ. The Cochrane Database of Systematic Reviews, 2011, Jul.;(7):1469-493X. (The likely reason: Micro-tears in the muscle and surrounding connective tissue are to blame for soreness, which stretching won’t repair.)

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.