Can you touch your hands to your toes? Some people consider this to be a good measure of how flexible you are. So what if you can’t? Some folks will tell you that you need to do more stretches – but does stretching really increase flexibility? Let’s see what science shows.
What Happens When You Stretch?
Muscle fibers are made up of units called sarcomeres, and each sarcomere contains contractile proteins called myofilaments. These include thick filaments, myosin, and the thin filaments, actin. When you stretch or elongate a muscle, the area of overlap between the myofilaments decreases, and if you continue to stretch the muscle, it pulls on the surrounding connective tissue. This whole process helps to realign any fibers that have fallen out of line, which is why stretching seems to be therapeutic.
Of course, you have to have a safeguard to protect your muscles from excessive stretching. That’s the job of proprioceptors called muscle spindles as well as Golgi tendon organs located at the muscle-tendon junction. If you overstretch a muscle, it activates specialized receptors called muscle spindles. The muscle spindles send a signal to your brain telling the muscle to contract in response to excessive stretch as a protective mechanism. Overstretching also activates Golgi tendon organs, which sends a message to the brain telling the muscle under tension to relax. You need this safeguard to protect your muscles from injury.
Flexibility and Stretching
What about the flexibility issue? The connective tissue in your joints has a certain degree of elasticity or “stretchability”, based on factors like age and genetics. Elasticity refers to the ability of muscles to recoil or return to their resting length after you stretch them. When you stretch a muscle, it increases the elasticity of the muscle and the muscle becomes longer but only temporarily. Depending on how long you stretched the muscle, it returns to its baseline length within a few minutes to an hour.
Since the increase in elasticity is temporary, how can stretching lead to a lasting increase in flexibility? After all, the muscle you stretched returns to its original length fairly quickly. It has to do with your nervous system. When you engage in a regular stretching program, the muscles you stretch become more tolerant to being stretched. This process is called plastic deformation and essentially means you’re training your nervous system to become more tolerant of being lengthened. As a result, you can lengthen a muscle more before your nervous system puts up resistance by activating Golgi tendon organs.
What stretching DOESN’T do is structurally change the muscle or make it permanently longer. You wouldn’t want that anyway since your risk for injury would be higher. It simply changes the muscle’s tolerance to being stretched or lengthened.
Is there scientific proof that stretching increases flexibility? A review carried out in 2002 looked at 13 studies. It showed stretching increases joint range-of-motion by an average of 8 degrees for more than a day afterward. The key here is “regular” stretching. For it to have more than a temporary effect on flexibility, you have to do it routinely.
Stretching for Injury Prevention
One reason people stretch is to lower their risk for injury. This is based on the idea that when you’re flexible your risk for injury is lower. In reality, research doesn’t necessarily support this idea. Studies looking at whether stretching prior to a workout reduces injury risk are conflicting. Some studies show a slight benefit, but a number also show no significant reduction in injury risk regardless of when stretching takes place. The take-home point: Don’t count on stretching to lower your risk for injury – there’s insufficient evidence that it does.
Unfortunately, there’s also no evidence that stretching reduces delayed-onset muscle soreness or DOMs. The idea that stretching reduces soreness after a workout began in the 1970s when people mistakenly thought delayed-onset muscle soreness was due to muscle spasm and stretching would lengthen the muscle and reduce spasm. Now we know DOMs is more likely due to microscopic tears in the muscle fibers and the inflammatory response that follows.
Dynamic versus Static Stretching
When you stretch, dynamic stretching offers the most benefits and the least risks. Some studies show static stretching, where you hold the stretch for more than 45 seconds, reduces muscle performance while dynamic stretching won’t harm performance and may slightly enhance it. A study carried out at the University of Zagreb analyzed 104 studies of athletes who stretched statically before a workout. Not only did static stretching NOT help performance, it reduced muscle strength by 5.5%.
Static stretching is where you lengthen and hold a muscle in a lengthened position for 30 seconds or more. Dynamic stretching is more like an active warm-up where you move your muscles actively through their full range-of-motion. A 2008 study showed athletes that did dynamic stretches each day for 4 weeks experienced improvements in flexibility, strength, speed, agility, and power. How’s that for benefits?
In general, experts recommend dynamic stretching BEFORE a workout and static stretching afterward. Avoid doing any type of static stretch prior to a workout when the muscle is cold. Static stretching is best reserved for the end of a workout when your muscles are warm. Stretching is particularly beneficial after a strength workout to help loosen the muscles you just worked.
The Bottom Line
Stretching DOES temporarily increase flexibility and may have sustained flexibility benefits if you engage in a regular stretching program. Why is flexibility so important? You lose flexibility as you age. Plus, being more flexible reduces the risk of falls and helps you perform better in certain sports. Being too stiff and rigid also impacts your posture and increases the work you have to do to carry out your daily activities.
Stretching isn’t the only way to improve your flexibility. Add a bi-weekly yoga routine to your workout. Research shows Hatha yoga improves strength, flexibility, muscle endurance, and balance. It’s a good way to diversify your workout too.
Now you know why flexibility is important and the limitations of stretching. To experience more prolonged improvements in flexibility, you need to stretch regularly and, preferably, add some yoga sessions to your routine.
Strength and Conditioning Research. “Does stretching really change muscle length?”
Cochrane Database Syst Rev. 2011 Jul 6;(7):CD004577. doi: 10.1002/14651858.CD004577.pub3.
Men’s Health. “The Biggest Muscle Soreness Myth”
WebMD. “The Truth about Stretching”
Time Magazine. “Why Stretching May Not Help Before Exercise”
ACE Fitness. “Does Yoga Really Do the Body Good?”