Yoga teachers and teacher trainers often make the claim that ligaments are not meant to stretch. They warn their students to avoid placing stress upon their joints out of a fear of stretching and destabilizing them. But this fear is not warranted by the science of our fascia. Not only do our ligaments, tendons, and fascia stretch, but they are supposed to stretch. They are naturally elastic—more so than our muscles!
Do I have your attention? What I just said may go against everything you have learned in yoga class or teacher training. Nonetheless, it is true. Ligaments, tendons, and joint capsules are all part of our fascia, and they are elastic and stretchy (which are not exactly the same things). Like all tissues, these tissues need to be exercised to remain healthy and strong.
Part of the confusion over whether or not we should stretch fascia arises from the different ways we use the term “elastic.” We commonly think of elastic materials, such as a rubber band, as those that can be stretched quite a bit and still return to their original shape when the stress is released. Since our muscles can usually stretch much more than our ligaments or tendons, and they do return to their original length, we think of muscles as being more elastic than ligaments or tendons (which don’t stretch very much). Normally, that is an okay way to think of the word “elastic.” But if we examine the scientific definition of elasticity, we find another way of thinking about the word. Our ligaments and tendons are actually more elastic than our muscles and it is a good thing that they are.
Imagine that you have three balls of equal size that you are about to drop on a hard concrete floor: a steel ball bearing, a rubber ball, and a ball made of raw pie dough. Which ball do you think is the most elastic? Let me ask the question in a slightly different way: Which ball do you think will bounce higher, assuming that all the balls are released from the same height? If you try the experiment, you may be startled to see that the very hard, stiff steel ball bounces highest. Despite there being no way that you can stretch that steel ball, according to the scientific definition, it is more elastic than the others. (1)
FIGURE 1: The steel ball on the left will bounce higher than the rubber ball in the middle because it is more elastic. The ball of dough on the right doesn’t bounce at all because it is plastic, not elastic.
Elasticity is not how stretchy something is, but rather “the ability of a body to resist a distorting influence and to return to its original size and shape when that influence or force is removed.” (2) The steel ball resists deformation more than the rubber ball, which resists more than the ball of dough. The dough ball simply flattens when it hits the ground. The rubber ball may deform a centimeter or so, while the steel ball deforms a millimeter or less. The energy that causes the deformation is returned to the ball when it bounces, but more energy is lost in the rubber ball than in the steel ball because of the rubber ball’s change in shape. (3) Thus the steel ball has more energy available to propel it higher after it hits the floor.
In the same way, our tendons and ligaments are more elastic than our muscles. This doesn’t mean they are stretchier (although some are, as we will see). Indeed, most are stiffer than most muscles. But because they are more elastic, our tendons and ligaments return more of the energy used to stretch them back into a movement in the opposite direction, much like springs do when they are stretched.
FIGURE 2: A stiff spring stretches less under the same force than a more compliant spring. Our tendons and ligaments are stiffer than our muscles, but this doesn’t mean that they are less elastic. They do stretch, just not as much. Cold or engaged muscles are stiffer than loose, relaxed, or warmed-up muscles, which will stretch more. But in this state, the stretchier muscles are less elastic than the stiff muscles.
We are the bouncing primate
Humans are the running, jumping, bouncing primate: Our hamstrings are more like hamsprings! Our fascia is different from that of our simian cousins—we bounce. Our Achilles tendon, for example, evolved to be longer, stiffer, and springier than in other apes. It can stretch, and when that stress is released, the Achilles tendon snaps back like a tight spring, helping us to run and jump. (4) The highly elastic nature of many fascial tissues, like tendons and ligaments, allows us to walk, run, jump, and even throw with great facility and efficient use of energy. This wouldn’t be possible if our ligaments and tendons couldn’t stretch.
Human fascia has evolved to stretch and elastically recoil. How much a tendon or ligament can stretch before being damaged is quite variable: It depends upon where it is, and to whom it belongs. One oft-cited statistic is that a tendon can stretch only 8 to 10 percent before becoming damaged. (5) However, that’s an average derived from studies of very small numbers of people. The Achilles tendons of athletes can elongate anywhere from a low of 6 percent (in some runners) to a high of 19 percent (in some swimmers). Even in a nonathletic population, the range of Achilles tendon elongation varies from 5 percent to 13 percent. (6)
Some ligaments are superstars at stretching! The ligamentum flavum along the spine can stretch 80 percent without damage! (7) Recently, even the very stiff iliotibial band has been found to be elastic, stretching about 1 to 3 centimeters when we're running. It acts like a very stiff spring that helps to bring the back leg forward when we walk or run. (8)
All of this shows that fascial tissues, including our ligaments and tendons, do, indeed, stretch. This is normal, healthy, and necessary.
FIGURE 3:We are the running, leaping, bouncing, and dancing primate, thanks to the elasticity in our tendons and ligaments.
Just because we can overstretch does not mean we should never stretch at all
Overstretching is a valid concern for fascia as well as muscles—overstretching any tissue is not good. But that does not mean we should never stretch at all. In fact, exercising our tissues too little can be just as harmful as exercising them too much.
Longer ligaments or tendons can enhance range of motion and mobility, especially for people who suffer from too little mobility. The good news is that we can train our fascia to be longer, stronger, thicker, and more elastic! But most people are more concerned about the springiness (i.e., elasticity) of their fascia than its length. Several studies have shown that while athletic training can improve the length of tendons and ligaments, (9) it can also increase their elasticity. (10) According to fascia researcher Robert Schleip, “Fascia adapts to regular stretching-loading demands—it changes its length, strength, and alignment. If tensile forces are frequently repeated, the collagenous fibers are strengthened and become more injury resistant. This is accompanied by a significantly higher elasticity capacitance…a greater capacity to act as a spring.” (11)
It is very clear that fascia, tendons, ligaments, and even joint capsules do stretch, should stretch, and can be trained to be even more elastic and stretchier. The question is, how?
How to safely exercise fascia
Schleip suggests that there are two ways we can use yoga to affect our fascia: through slow, static stretches, and with small, bouncy movements when the fascia is already slightly stretched. The former will affect the length of the fascia, the latter its springiness. (12)
Slow, static stretches include holding stress in a posture for a few breaths (as done in normal hatha yoga classes) or for several minutes (as done in the yin yoga style of practice, which he highly recommends).
For the bouncing practices, he suggests exercises using jumping or swinging movements that employ elastic recoil movements. Think of the jumping jacks that you used to do in gym class, or swinging your arms back and forth around you, or skipping rope, or bouncing push-ups against a countertop, or, indeed, those bouncy movements in a kundalini yoga class! Any movements that are bouncy and not too weight-bearing can serve.(13) These movements load the fascial tissues and release their energy into movements in the opposite directions. This can be a great alternative or addition to the opening asanas and flows at the beginning of a yoga class (such as sun salutations). Add some bounce to your practice. Do some jumping jacks, bounce on your toes, or exchange some bouncy burpees for chaturangas.
FIGURE 4: Bouncing movements at any age can help regain and maintain fascial elasticity.
How often? Not very! It turns out that our fascia doesn’t need to be constantly exercised. Even 10 minutes of bouncing two to three times a week should be sufficient to maintain elasticity. However, if your intention is to regain lost range of motion, more time may be needed to work specific areas. Perhaps two to three juicy yin classes a week will do the trick. As in all things, you will have to determine what works best for your body, given your lifestyle and capabilities.
The dangers of too little stress
If we avoid stressing tissues, we invite atrophy—a slow, steady decay of the tissue’s abilities. This happens to any tissue we avoid exercising, including our fascia. Lawrence Dahners, professor emeritus of orthopaedic surgery at the University of North Carolina, noted that “A common clinical finding is that unloaded ligaments not only atrophy, but also undergo contracture.(14) ” In other words, if we are not stressing our ligaments, our joints tighten up and we lose range of motion. (15)
Stretch those ligaments!
In short, our fascial tissues are designed both to facilitate movement and restrain too much of it. And, just like our muscles, they are elastic: They build up internal tension when stretched and can release that energy back into strong, quick movements in the opposite direction. These fascial tissues include our tendons and ligaments,(16) which are in series with our muscles, as well as the layers of fascia parallel to our muscles, surrounding and investing them. Even one of the strongest, stiffest pieces of fascia in our body, the iliotibial band, is elastic. Like other fascia, it is designed to stretch, and that is a good thing.
So, don’t be afraid to stretch your fascia—including your tendons and ligaments. Just don’t overdo it. How will you know if you’ve gone too far? If it hurts, you overdid it. But that warning applies to all tissues, including your muscles. Just because it’s possible to do too much doesn’t mean you shouldn’t do anything at all. So go ahead! Stretch those ligaments. Put that spring back in your step, and enjoy feeling younger and bouncier.
1. My thanks to Jules Mitchell for this thought experiment, which appears on page 121 of her book (Pencaitland, East Lothian: Handspring Press, 2019). It is an excellent resource to learn about the biomechanical nature of elasticity, stretch, creep, stiffness, and compliance.)
2. From Wikipedia: https://en.wikipedia.org/wiki/Elasticity_(physics)
3. The deformation of the pie dough ball is quite extreme and causes almost all the energy from its fall to be dissipated through its flattening. The rubber ball is much stiffer, but it too changes shape, and this deformation takes away some of the energy from the fall, converting it into heat. The steel ball changes shape very little because of its greater stiffness compared with the other balls. Thus, almost all of the kinetic energy from its fall is available to help it rebound back up.
4. In humans, a resting Achilles tendon averages about 10 centimeters in length, but in chimps and gorillas it is barely one centimeter long. This is one of many adaptations that allows humans to run longer than other primates. See Daniel E. Lieberman, The Story of the Human Body: Evolution, Health, and Disease (New York: Pantheon, 2013), 85–86.
5. See Savio Woo, R. Debski, J. Zeminski, Steven Abramowitch, S. Saw, and J. A. Fenwick, “Injury and repair of ligaments and tendons.” Annual Review of Biomedical Engineering, 2. (2000): 83–118.
6. See Toshiyuki Kurihara, Ryuichi Sasaki and Tadao Isaka, “Mechanical properties of Achilles tendon in relation to various sport activities of collegiate athletes.” 30th Annual Conference of Biomechanics in Sports. Melbourne, 183 (2012). The ranges I cited come from adding or subtracting two standard deviations from their best and worst cases. This gives the boundary measurements between which 95 percent of their subjects fall.
7. See Susan Standring, ed., Gray’s Anatomy, 41st edition (Elsevier, 2016), 115, 745. When the spine is fully flexed, the ligamentum flavum is stretched fully, but even in the deepest backbends it still has some tension in it. This is due to its high elastin content and probably serves to prevent buckling during backbends that could push the ligament into the spinal cord.
8. See C. M. Eng, A. S. Arnold, D. E. Lieberman, and A. A. Biewener, “The capacity of the human iliotibial band to store elastic energy during running,” Journal of Biomechanics. 48, no. 12 (September 2015): 3341–8.
9. See Kurihara et al., 2012.
10. See Gaspar Epro, Andreas Mierau, Jonas Doerner, Julian Luetkens, Lukas Scheef, Guido Kukuk, et al., “The Achilles Tendon Is Mechanosensitive in Older Adults: Adaptations Following 14 Weeks Versus 1.5 Years of Cyclic Strain Exercise,” Journal of Experimental Biology 220, no. 6 (March 2017): 1008–1018 .
11. Riva Verlag in Robert Schleip, Fascial Fitness (Lotus Publishing, 2017) 72.
12. This is not to imply that slow, static stresses only affect the length of our tissues. There are a whole host of other benefits that arise, as Schleip describes: activating the parasympathetic nervous system, reducing blood pressure and heart rate, initiating the relaxation response; decreasing inflammation and chronic pain; and there are purported mystical effects (91).
13. It is not a great idea to do jumping jacks while holding kettlebells. Your body weight is sufficient.
14. See Lawrence Dahners, Laury Dahners’ Orthopedic Page, accessed January 10, 2020. http://laury.dahners.com/orthoprofessional.html.
15. I could be more pedantic and discuss the difference between “stress” and “stretch”: stressing tissues is the biggest key to health. Whether they stretch as a result of the stress is not as important. They may stretch; they may not. The key is the stress placed upon the tissues, which creates mechanotransduction signals at a cellular level, stimulating growth. However, the point of this article is to remove the fear of stretching ligaments and tendons, so it is not so important to go into the difference between stress and stretch. It is okay to stretch these tissues, but most important is to stress the tissues, whether they stretch or not.
16. The fact that ligaments are in series with the muscles is a newer realization. While most textbooks still show the ligaments being in parallel to the muscles, the work of Jaap van der Wal sheds new light on this old model. See Jaap van der Wal, “The Architecture of the Connective Tissue in the Musculoskeletal System,” International Journal of Therapeutic Massage and Bodywork 2, no. 4 (2009): 9–23.