A lot of people initially come to their first yoga class because they would like to be more flexible. And, conversely, I also hear from people who resist trying yoga because they think they need to be flexible in order to start yoga. But what does flexibility actually mean? And where does it really intersect with yoga? In this blog, we’ll dive a little deeper into some related terms, flexibility, stretching, and hypermobility, and we’ll look at how those concepts come up in our yoga practice.
What is flexibility?
Flexibility is generally defined as our ability to access a full range of motion. But, if we want to be more precise, our flexibility is specific to individual joints. We might be moderately flexible at our shoulder joints, but have less than an average range of motion at our ankle joints for example. However, we might describe someone as either very flexible or not very flexible, both generally and in their yoga practice, if they have more range of motion than average or much less than a full range of motion at most joints in their body.
What affects our flexibility?
- Activities we do or don’t do. That might include hobbies we have that create residual muscle tension. Or, it might be that we sit a lot. We can get “tight” from both activity and inactivity depending on our particular genetic proclivities.
- Sports we train for
- Age. All else being equal, our flexibility naturally decreases as we age. Generally, our tissues can dry out due to lifestyle choices as we get older and that affects our flexibility.
What is stretching?
Stretching could be generally defined as lengthening muscle tissue and accompanying fascia with the intent to maintain or increase range of motion. And, there are different types of stretching that are appropriate for different situations. For example, there are static types of stretching that involve holding a stretch for a certain length of time. This is the kind of stretching most common in yoga practice.
Proprioceptive neuromuscular facilitation (PNF) stretching techniques involve taking advantage of various neuromuscular principles such as actively engaging a muscle against a resistance and then relaxing it to create a stretch. This takes advantage of a principle associated with the relaxation phase that occurs after a contraction happens.
Just as strength training has multiple benefits and is good for us in different ways, stretching has multiple benefits too. Stretching helps us maintain, or even increase, range of motion at the joints in our body. This is important because maintaining range of motion and flexibility can help prevent injuries from all kinds of sports, athletics, and leisure activities. Additionally, we tend to dry out and get tighter as we age. So, keeping up with an activity like yoga which has a stretching component can slow that process.
Recent research suggests that stretching is even good for other systems in our body, like our cardiovascular and immune systems. For example, one review paper reported that stretching improved cardiac autonomic function (Wong and Figueroa, 2021). Additionally, another review paper reported a positive relationship between stretching and reduced inflammation even at a molecular level (Krol et al., 2022). So, there are lots of good reasons for us to maintain a stretching routine.
What happens when we stretch?
The short answer is we don’t actually know what the mechanism is for stretching to result in increased range of motion. There may be mechanical changes that occur, but research is currently unclear on that. Additionally, if there are mechanical changes, it seems that they require a more significant duration, intensity, and/or repetition than most experimental stretching protocols have used in research studies so far. For example, a review study from Freitas et al., 2018 found that stretching protocols of less than eight weeks, most with five repetitions of an individual stretch duration of 30 seconds or less, repeated 5-7 days per week did not increase muscle extensibility, but did increase stretch tolerance.
Sensory and proprioceptive changes
There may be changes that occur in the nervous system when we stretch. For example, Folpp et al., 2006 reported that hamstring muscle extensibility didn’t change after a stretching regime of 20 minutes a day, five days per week, for five weeks, but tolerance to stretch did, which resulted in increased joint range of motion. Similarly, Ben and Harvey, 2010 found that muscle extensibility in the hamstrings didn’t change when participants stretched for 30 minutes, five times per week, for six weeks. But, they did find that tolerance to increased stretch increased which resulted in an increased joint range of motion at the hip joint (Ben and Harvey, 2010).
Central nervous system involvement
We don’t know exactly how the central nervous system operates to relay signals between our muscles, fascia, and other connective tissues and our resulting movement or lack of movement. Generally, the central nervous system receives information from muscle spindles that are embedded in our muscles and which have different types of sensory endings that bring in sensory input (Banks et al., 2021). This system is involved in our ability to sense changes in muscle length and our awareness that we are holding a stretch (Banks et al., 2021).
Of course, both mechanical and sensory changes may occur. There is so much that we don’t know about what happens when we stretch. There are likely additional changes to the mechanical and sensory changes that we’ve mentioned, that we haven’t uncovered yet. And, anecdotally, those of us who have done yoga practice for many years know that our range of motion and flexibility changes when we practice yoga. So, it’s okay that science hasn’t figured out exactly what’s happening to us while we continue to enjoy the space in our bodies.
How should I stretch?
Types of stretching
Many studies haven’t found a consistent difference between the effectiveness in increasing range of motion of static stretching, ballistic stretching, and proprioceptive neuromuscular facilitation (PNF) techniques. For example, there was no difference between the effects of a hold and relax type of stretch and static stretching on hamstring flexibility (Ahmed et al., 2015). A review paper by Thomas et al., 2018 reported that all three types of stretching evaluated (static, ballistic, and PNF techniques) increased range of motion. However, static stretching produced greater gains in range of motion than the other two types. Similarly, Konrad et al., 2023 reported that static stretching and PNF techniques produced greater gains in range of motion than ballistic/dynamic-type stretching. Conversely, Meroni et al., 2010, reported that active stretching resulted in greater knee extension range of motion than static stretching of the hamstring muscles specifically.
Duration, frequency, and intensity
What does seem likely is that duration, frequency, and intensity matter. Curiously, the study that showed mechanical changes in muscle length after stretching was the study that more closely resembled the frequency of how we might practice over the long term in yoga. One review paper recommends stretching at least five minutes in duration and at least five times per week in order to see gains in range of motion (Thomas et al., 2018). Most yoga practices done consistently will more than cover that duration.
That recommendation is another reason to practice yoga consistently. A review paper from Konrad et al., 2023 noted that even when studies didn’t show a significant effect of the amount of stretching (dose-response), it was likely because all of the stretch durations were fairly low compared to what we might do in a yoga practice.
A separate study found that the highest stretch intensity protocol produced the greatest increase in joint range of motion (Freitas et al., 2015). However, Konrad et al., 2023 note that stretching to a level of intensity that causes pain is not necessary. Lower intensity stretching still resulted in significant increases in range of motion.
When to stretch?
Recent research suggests it’s not recommended to stretch immediately before you want to do a dynamic movement. There is some indication that stretching immediately before an athletic activity could reduce some kinds of muscle activity temporarily. For example, de Cerqueira et al., 2020 found that static stretching immediately before being subjected to a simulated ankle sprain reduced the muscle activity of peroneus (fibularis) brevis and longus and increased the time it took for them to respond to the cue to contract. Similarly, Nakamura et al., 2021 found that static stretching of the medial gastrocnemius reduced muscle strength immediately after. Generally, if your goal is increased range of motion, then it makes sense to stretch when your muscles are relaxed and you’re not trying to contract them.
What is hypermobility?
Hypermobility is a naturally existing range of motion that is greater than average. “Hyper” means more than. “Mobility” of course refers to movement. So, you could put those definitions together to get that hypermobility is considered “excess mobility.”
Hypermobility and related issues
We can apply the term hypermobility to specific joints in the body or we can use the term to describe someone’s overall greater-than-average mobility at most joints. Hypermobility occurs along a spectrum. It ranges from greater than average mobility at a specific joint all the way to connective tissue disorders. Hypermobility spectrum disorders like Ehlers-Danlos syndrome refer to a condition of extreme hypermobility that has potential health complications.
Do hypermobile people still need to stretch and lengthen muscles?
Yes! Those with hypermobile bodies still experience the same benefits of stretching and lengthening muscles as less flexible people. However, gaining flexibility should not be the aim. Additionally, those who are hypermobile need to go more slowly and pay attention to the sensations of lengthening tissues. Research suggests one reason for greater flexibility may be a delayed response of sensation to stretching. People who are very flexible and on the spectrum of hypermobile may need more time to develop proprioception and a functional connection to their deeper musculature. They may also have a different ratio of collagen to elastin at that level of structure.
Hypermobility and yoga
What’s important is that practitioners that are on the hypermobile end of the flexibility spectrum take as much time as needed when doing activities like stretching or yoga to really feel and respond to the sensations in their body. Some research suggests that it takes longer than average for the bodies of more flexible people to send and/or receive the cue that they are at their end of range of motion. So moving too quickly into deep ranges of motion could have an increased risk of strain. Additionally, there may not be intense sensations for very flexible people in every pose. If you are moving your body through a fairly full range of motion, then you are likely getting all the benefits of stretching, even if you don’t feel a lot of “stretch sensation” in many poses.
Women and flexibility
Questions about gender and its relationship to flexibility, stretching, and yoga sometimes come up when we start talking about flexibility more generally. Are women more flexible than men? Yes, while there are of course exceptions to that trend, women are generally more flexible than men. For that reason, the effects of yoga, or simple stretching, on flexibility, may differ.
In some cases, men as a group, showed a greater increase in flexibility than women during studies on stretching, presumably because they started with less initial range of motion. For example, Inal et al., 2021 found that while both male and female practitioners increased their flexibility after yoga, male practitioners as a group showed a greater increase in flexibility than females. However, in other studies, women showed a greater increase (Rayamajhi et al., 2014). For example, Konrad et al., 2023 reported in a review paper combining the research of many previously published studies that although both sexes increased their range of motion after practicing yoga, there was a greater increase for women. This was possibly due to a greater proportion of slow twitch fibres compared to men, allowing for a greater change in range of motion more quickly.
However, in other cases, there was no difference in change in range of motion between genders after completing certain stretching protocols (Yu et al., 2022). Unsurprisingly, it seems that differences and similarities between the amount of change in flexibility between female and male practitioners depend on specifically which movement is being done.
Yoga and flexibility
So, does yoga increase our flexibility? Yes, both research and anecdotal experience support the idea that consistent yoga practice results in greater range of motion. For example, many research studies, including larger review studies that summarize many smaller studies, support yoga’s ability to increase our flexibility (Luo and Huang, 2023; Sivaramakrishnan et al., 2019; Field, 2016). However, it’s important to keep the concept of what yoga does in perspective. Every yoga practice doesn’t include stretching every muscle.
If there are specific issues you’re working with in your body, or you’re using yoga to maintain range of motion for a particular sport, for example, then you likely need to tailor what specific postures and types of yoga you choose for the goals that you have. Additionally, those considering yoga often don’t give it a try because they have an idea that you need to already be very flexible to begin. But, this is simply not true. Yoga is one way that you can increase flexibility whatever your level of stiffness.
Is flexibility the purpose of yoga?
While there is a lot of emphasis from both media and exercise enthusiasts on the ability of yoga practice to increase flexibility, if we’re taking a wider view, then physical flexibility is not the ultimate goal of yoga. Flexibility is not mentioned at all in Patanjali’s Yoga Sutras and is only tangentially mentioned in the Hatha Yoga Pradipika. The ultimate purpose of Yoga according to the texts is not stretching, but recognizing our unity with consciousness. While there are many benefits to increasing our flexibility and range of motion, especially when we spend so much of our time sitting, it’s important to remember that on some level, it’s not the ultimate aim of Yoga.
Having said all of that, it is also reasonable to consider that our body is some form of representation of who we think we are. Our sense of self is at least partly wrapped up in our body. As a result, working with our body is a reasonable way to start a journey of self. As we build a greater sense of comfort in our physical body, this may also inform a greater sense of our comfort with what we think we are mentally, and emotionally. That is not to say that stretching and moving in yoga will fix all of these, but it will more likely than not help us understand ourselves, physically, mentally, emotionally, and even spiritually.