For many people, stretching is often filed under the "things I think I should do more often but don't" category. (See also: flossing and digital detoxing.) But it turns out, many of the things we've been told all along about stretching aren't necessarily accurate. And in some cases, it may not be as beneficial as you think.
The thing is, the science just isn’t there yet for researchers to give definitive best practices for stretching—what's helpful, what's not, and what's (potentially) harmful, across the board.
"There's a lot of controversy surrounding stretching right now," Jan Schroeder, Ph.D., chair and professor of fitness in the department of kinesiology at California State University, Long Beach, tells SELF. "Out of all of the kinds of activity, stretching [recommendations from the American College of Sports Medicine] have probably changed the most frequently because we're still learning a lot about it."
That said, there are some things we do know about stretching. While some of the supposed benefits of stretching have been overhyped, being more flexible can definitely play an important role in improving your workouts.
Here's what the research and the experts we reached out to have to say about what stretching is, what it can do, and what it can't.
First, let's dive into what's happening in a muscle when you stretch it.
"The muscle is [mostly] made of protein fibers," Mike Ramsey, Ph.D., professor and chair of the department of sport, exercise, recreation, and kinesiology at East Tennessee State University, tells SELF. The basic functional units of muscle tissue are called sarcomeres. Sacromeres are made up of fibers called contractile proteins. As the sarcomeres contract, these proteins "weave" closer together, and as they relax, they pull further apart. Connective tissue in your muscles also stretches out along with these contractile proteins.
Between these muscle fibers, you have sensory receptors (basically nerve endings) called muscle spindles. "They are what monitor the length and the tension of the muscle," says Schroeder.
If the muscle is stretched too quickly, Schroeder says, the spindles will initiate the stretch reflex. This causes the muscle to shorten and protect itself from being overstretched," says Schroeder. In other words, your muscle fibers contract and say "Nope, we're not relaxing," because your body thinks it's at risk for injury. If you’ve ever leaned into a stretch and been met with some resistance, you’ve experienced this. If you fight past that resistance and push yourself too deep into a stretch while your muscle fibers are trying to contract against your efforts, you can end up hurting yourself by damaging your muscle, tendons, or ligaments. Over time, the more regularly you stretch a muscle, the less sensitive the muscle spindles get, which means the stretch reflex won’t be so strong. You're basically telling your body, “Hey, I'm not trying to hurt you—we can relax.” (There’s another receptor called the Golgi tendon organ, or GTO, that comes into play here, too. Its job is to trigger an inverse stretch reflex, which tells the muscle it’s OK to relax.) Eventually, you’ll be able to lean deeper into that stretch.
Different types of stretching seem to be better suited for different situations.
The two main types of stretching you've probably heard of are static stretching (where you hold a stretch in place) and dynamic stretching (where you're moving through a range of motion that in turn stretches out your muscles).
Dynamic stretching is usually included in a dynamic warm-up before a workout. With smooth, controlled motions, the goal of this type of stretching is to prepare your body for the work it's about to do, says Schroeder. "When we do dynamic stretching, we're slowly warming up the joint area and the muscles surrounding that joint," she says. It also starts preparing the neural pathways involved in the exercise you're going to be doing—muscle contractions are largely regulated by the brain, so dynamic stretching helps get that mind-muscle connection ready to go.
Static stretching, on the other hand, means holding a position for a set amount of time, like doing a standing quad stretch for 30 seconds. Guidelines for the optimal time to hold a static stretch vary, but some physical therapists give a general recommendation of about 30 seconds; Schroeder says not to stress about the time and just hold until you feel a deep, satisfying stretch.
For many people, static stretching can potentially be beneficial.
The biggest draw of static stretching (when it comes to fitness) is that it can improve your joint mobility, says Schroeder. Because your joints work in conjunction with the surrounding muscles, the more mobile your joints are, the better your range of motion will be. A greater range of motion will help you move through pretty much any exercise and daily activities with greater ease. This also means you’ll likely be able to get more out of your exercises—for example, being able to sink deeper into a squat will hit more muscles than if you can only lower down a couple inches.
Beyond simply increasing joint mobility and range of motion, static stretching can also be useful for improving body alignment and preventing everyday pain and injury, says Schroeder. This is especially true if you spend a lot of your day sitting down.
Consider this. "If you're sitting all day, those hip flexor muscles are starting to shorten, and that's going to pull down the pelvis, so you're going to get that anterior [forward] tilt,” says Schroeder. Now, think about what's going to happen in the back—because those hip flexors are so short, you’re pulled forward and your lower back becomes really arched. Now you're not in a biomechanically sound position to support the rest of your body, and you're going to have pain in other areas." The good news? Stretching can help remedy this.
Plus, stretching can be a good way to end a workout. "It's a nice way to psychologically finish a workout," says Schroeder. "The body's coming back to homeostasis." Stopping abruptly can cause blood to pool in your legs (instead of promptly recirculating to your heart and brain) and make you feel dizzy or faint, so stretching is a nice way to cool down and transition your body from workout to rest.
But there's some debate over how worthwhile static stretching really is for everyone.
Some experts—including Schroeder—believe that if you’re active on a regular basis, you’re probably already doing enough dynamic stretching through exercises like squats, lunges, and more, and in that case tacking static stretches onto your day might not add much additional benefit. "Is [static stretching] really necessary [for everyone]? I'm on the fence about it, to be honest," says Schroeder.
You may have heard that stretching is important because it can help prevent injuries or make you a better athlete, but the truth is, the research doesn’t really confirm that it can do either of those things. At least, not for every person doing every type of exercise.
For example, one 2017 review published in the journal Research in Sports Medicine, which set out to determine how stretching impacts performance and injury risk in long-distance runners specifically, found that, according to the research that’s available, stretching probably won’t help most people run faster or fend off overuse injuries. But the review authors also noted that, according to some of the studies they looked at, it seems that a regular stretching routine may be able to reduce the likelihood of muscle and tendon strain injuries in some activities (like sports that involve quick, explosive movements, for example). Until more specific and widely applicable research is done, there’s no way to say what the optimal amount of stretching is, if any, for your exercise of choice. Cue the standard advice: In the meantime, do what feels good for your body, stop if anything feels painful, and always check with a doctor if you change your fitness routine.
Research does suggest, though, that static stretching right before a workout may not be a good idea.
While dynamic stretching before a workout can be beneficial, research suggests that static stretching before a workout may actually negatively impact muscle strength and your ability to perform explosive movements (like jumping or sprinting).
Granted, this may not be a huge concern for the average exerciser, says Nelson. "The people who need to worry about it are not your weekend warriors—you're talking about more of the elite group where it really becomes a factor," says Nelson. But if you're aiming for a performance goal (like in a triathlon or marathon), it’s probably best to avoid static stretching before training. In fact, the same Research in Sports Medicine review suggests that endurance athletes may be better off warming up with just a low-intensity, progressive run.
One of the most pervasive stretching myths is that it can prevent or heal sore muscles. It can’t.
Stretching has its purposes, but the truth is, it can't do everything it's purported to do. For example, stretching pre- or post-workout won’t stop you from getting sore or heal delayed-onset muscle soreness (DOMS) any quicker.
"There's really no evidence that shows stretching prevents or alleviates DOMS," says Ramsey. In fact, a 2011 review concluded that stretching before or after a workout didn't prevent DOMS to a significant degree.
Stretching also can't heal regular soreness or DOMS that's already been set in motion. Soreness happens after you've broken down muscle fibers as a result of resistance training (and while soreness isn't a good marker for the quality of a workout, this "rebuilding" process is actually what makes your muscles stronger). DOMS is a higher degree of soreness, and it usually peaks about 48 to 72 hours after a workout as your body gets to work repairing those tiny microtears in your muscle fibers.
The bottom line: Stretching can't prevent you from breaking down muscle fibers in a workout, and it can't heal damaged muscle fibers either. In the case of DOMS, the only thing that really works is time (getting the blood flowing through light exercise like walking or low-intensity biking may help, too).
That said, gentle stretching may help you find some temporary relief. "Stretching has been shown to maybe relieve muscle spasms or cramps," says Nelson. So it might help your muscles feel a little less tight in the moment, even though it won't help actually repair them. If some gentle stretching feels good, go for it, but don't feel obligated.
The bottom line? Stretching is good, but not stretching really isn’t the worst.
In addition to dynamic warm-ups before a workout, doing some static stretching a couple of days a week is a reasonable approach, says Schroeder. No need to overcomplicate things—tack on 5 to 10 minutes at the end of a workout to cool down with some static stretches, or get on the floor and stretch during a commercial break (just walk around for a couple minutes first if you've been sitting to get the blood flowing first).
And hey, sometimes, stretching it out just feels good—and that's a pretty great reason to do it, too.