A: Before we answer this reader’s question, we will provide some background on flexibility and stretching in general. To start, let’s clarify exactly what we mean by “flexibility.” One definition that we like is:
Flexibility is defined as the ability to move through a specific joint range of motion (ROM)
For example, good range of motion in the hip joint in a forward fold (flexion) means being able to fold your hip joint towards your belly to about a 160-degree angle when your knee is bent. If you discovered that your hip range of motion in this direction was limited to about 90 degrees—which would definitely restrict your ability to do some of your daily activities (such as bending your knee in to put on your shoes)—you might want to increase your range of motion/flexibility at that joint. Can stretching of the sort we do in yoga eventually improve your range of motion at the hip? Let’s start by looking at how stretching in general helps.
How Stretching Improves Flexibility
Studies have shown that stretching increases muscle length (known as extensibility) and increases range of motion at the joints. The exact mechanisms that cause these effects are not clear yet but may include mechanical changes in the myofascial tissues and/or in the neural connections of muscles and brain, or in decreasing the intensity of sensation that deep stretch causes (called “stretch tolerance”).
The studies have also shown that improved range of motion at the joints and increased muscle length occur as a result of both static stretching and dynamic stretching. They also note that for younger people, a static stretch of 15-30 seconds may be adequate for both short- and long-term results of changing resting length of the muscle and improving range of motion of the joints, but for older adults over 65, longer holds may be needed, up to 60 seconds. In addition, the study on the muscle protein titin that we mentioned in Static Versus Dynamic Poses suggests that static holds of 90 seconds or longer may actually lead to better gains. All these finding have influenced our recommendations for how long to hold poses below.
Other studies on stretching to improve flexibility have shown that when performed regularly over a long period of time stretching improved flexibility in hamstrings, calves and ankles, as reflected by increased joint range of motion. Not so impressive is the finding that the effects of short-term stretching or infrequent stretching don’t last much longer than one day or so. So if you if you don’t stretch regularly, after a day or two, muscles return to pre-stretch length. But you can overcome this by doing “held” or static stretches three or more times a week—perhaps good motivation to have a regular home practice!
Quite interestingly, long-term stretching regimens have actually been shown to improve performance in physical activities—from various sports to every-day physical activities—over time, as well as improving overall strength. How unexpected and fascinating that regular stretching can lead to improved strength! Although the mechanisms are complex and incompletely understood, passive and active stretching is thought to lead to muscle hypertrophy (growth). The results, however, are welcome! If you want to know more about it, see http://www.somastruct.com/stretching-a-form-of-strengthening/.
Ways of Stretching with Yoga
There are two main styles of stretching that yoga provides: dynamic and static. In dynamic poses, the stretches are very brief, as you move in and out of the stretch with your breath. In static poses, you hold the stretch for period of time, but that period can range from quite short (say, 10 seconds) to quite long (2 or 3 minutes or longer for restorative poses). How do you choose when to do which?
If you are doing yoga stretches to improve your performance in other activities, such as running or some other sport, studies have shown that static, held stretches greater than 45 seconds can actually reduce performance right after stretching. On the other hand, dynamic stretching seems to have no negative impact—and maybe slightly positive impacts—on sports performance. So I’d recommend that you don’t do long static yoga stretches right before you head out for an hour of cycling or a long stint at the rock climbing gym. Save the static stretches for afterwards or put a day in between a good yoga practice and your other favorite physical activity.
On the other hand, if your goal is to go further into more challenging poses that require better flexibility, we find dynamic stretches do lead to immediate improvements in muscle flexibility that we can then further with a static hold of the same pose. For example, moving dynamically in and out of Standing Forward Bend (Uttanasana) leads to improved hamstring/hip flexibility, which can then be increased even more with a long hold of the pose.
How Long to Stretch?
Finally, getting back to the original question: how long should you stretch for maximum benefit? Because of the research that shows the protein titin, which is found in muscles, changes shape and may contribute to a stretch lasting for several days when a stretch is held for longer periods of time, say 90 seconds (see Yoga and Flexibility: An Overview, we recommend a combination of small dynamic sequences of stretches done for 6-8 repetitions, followed by holding the stretch for 90 seconds. For example, if you are trying to stretch the fronts of your thighs (psoas and rectus femoris muscles), you could move dynamically from Extended Child's pose to Cobra pose and back for 6-8 rounds, and follow that by holding Cobra pose for 90 seconds.
In general, with consistent practice, you can see results after at least three to eight weeks. As for how often and when you stretch, that depends on your goals:
1. If you are taking up yoga to improve your flexibility and strength for a sport, such as running or rock climbing, which take advantage of both flexibility and strength, then do your yoga stretches, dynamic and static, on days other than your sport days. On your sport days, you could do dynamic stretches before the sports activity since they don’t negatively impact performance, but skip the static stretches.
2. If you are taking up yoga to combat the stiffening and tightening of your body from years of sitting at work, you can do your stretches anytime you want. As we always recommend, start out with a shorter daily home practice that you can do comfortably, and gradually add more time and challenge to your stretches as you advance. If you stretch a particular muscle or muscle group regularly, probably do it no more than every other day (we don’t want to overdo it and cause overuse injuries!).
3. If you are doing yoga asana regularly and your goal is to master more challenging poses, you will want to be consistent in stretching over several weeks to look for noticeable changes in flexibility. To give your body time to rest and repair, you will want to alternate intense stretching days with other types of yoga practice, whether that is an active, challenging practice, a gentle or restorative practice, or pranayama/meditative practice on your “off days.”
Although we have tried to go in great detail here about what we know about stretching, we have no doubt there will be more to share in the future. So, until then, happy stretching!
—Baxter and Nina
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