Summary Points:

  1. Flexibility is a critical component of fitness and overall good health
  2. Stretching is critical to improving our flexibility
  3. There are a number of stretching techniques that have useful application
  4. Traditional static stretching can be effective, but it’s necessary to hold the stretches for a 30 seconds or more. Because the sensation of static stretching can be unpleasant most people don’t hold their stretches long enough
  5. Undulating, wave-like stretching, that involves deep rhythmic breathing is an effective alternative

I suspect that practically anybody who might be reading this has, at some point in their lives, done some stretching to try to improve their flexibility. It seems common knowledge that stretching is good for us, that being flexible is important to our overall health and fitness, and that we’d perform better in sports and life if we stretched consistently. But, judging by how few people do it consistently, or even sporadically, we must assume that its value is either under-appreciated or the experience must be unpleasant or uncomfortable. From my own perspective, I believe that both are true. The value of regular stretching is under-appreciated, and most people do find the experience of stretching unpleasant, even painful. It’s no wonder it’s often the more neglected aspect of our fitness.

For a number of weeks, I’ve been writing about flexibility. In the first part of the series, we introduced fascia, that fascinating tissue that connects, supports, and communicates with every part of our anatomy. We explored what causes us to feel tightness or stiffness in Part Two. We moved on from there to explain how Myofascial Release can help to improve our flexibility. In this article we are finally focusing on the subject that the majority of us are most familiar with, stretching. We’ll try to explain how and why it works, when it’s best to stretch, and how long and how often it should be done. And we’ll wrap up with encouragement that regardless of the how’s and why’s, we know from vast anecdotal experience and scientific evidence that it does work, it is important to our fitness, and it does not need to be unpleasant.

Before we dive in let’s revisit some key concepts associated with flexibility and stretching.

If you are familiar with these concepts, skip down to How Does Stretching Work?

Physical therapists regularly measure active range of motion (ROM) using a goniometer
Physical therapists regularly measure active range of motion (ROM) using a goniometer

Range of motion (ROM) describes the range of joint mobility around any specific joint. How far is each joint capable of moving through all of the directions that it is designed to articulate? How far should it be capable of articulating? We’ve looked at the elbow before to describe this concept. When at full extension, the expected limit of the elbow’s ROM, the arm should be relatively straight. At full flexion, with the elbow fully bent, we should be able to touch our shoulder or chest with our fingers. It’s possible to have an excess of ROM, known as hyper-mobility. We’ve all seen this when a person’s arm looks slightly bent back on itself with the elbow hyperextended. Likewise a joint can be hypo-mobile, in which it is unable to articulate the expected full range of motion. Looking again at the elbow, this would manifest as being not quite able to fully extend the elbow to straighten the arm.

Extensibility is defined as a muscle’s ability to extend to a predetermined endpoint. In most cases, the limits of extensibility are discovered by human sensory feedback. When we reach that predetermined limit, we experience discomfort or pain.

An interesting aspect of our muscles and fascia is that they are both elastic and plastic. They are elastic in that they will stretch as loads act upon them, returning to their original shape and length once the load is removed. They also demonstrate plastic properties in that if sufficient force is applied over an adequate period of time, they can permanently elongate. Naturally, if too much force is applied the muscle and fascia can tear or rupture. But, short of the point of catastrophic injury, it is possible to increase the extensibility of our muscles more permanently.  This property is known as plasticity.

Stretching is our attempt to elongate our muscles and connective tissues to improve ROM and flexibility. It involves all of these concepts listed above.


How Does Stretching Work?

OK, so how does it work? Are we truly capable of increasing the extensibility of our muscles? Are those increases permanent or transient?

There is considerable debate amongst the various scientific communities about how stretching works, if it works at all. The various theories can be attributed to the following five categories:

  1. Viscoelastic deformation
  2. Plastic deformation of connective tissue
  3. Increased serial sarcomeres
  4. Neuromuscular relaxation
  5. Sensory theory of extensibility

If you’re not really interested in the scientific “how” of stretching, please skip this next section and jump down to What’s the Most Effective Technique?

Viscoelastic deformation: this theory suggests that our muscles, fascia, and tendons have properties that are simultaneously elastic and viscous. The elastic properties are easy to imagine. As described earlier, once a load, or tension, is removed from a muscle it will shorten to it’s static resting state and length. But because muscles are thought to also be viscous, if they are elongated a sufficient degree on length and time, they will remain in that elongated state for some period of time before slowly returning to their original resting state.

Stretching a gummy worm is a good example of viscoelastic deformation.
Stretching a gummy worm is a good example of viscoelastic deformation.

“When stretch is applied to a muscle and the muscle is held in the stretched position for a period of time, as is the case with normal static stretching techniques, the muscle’s resistance to stretch gradually declines. This decline in resistance to stretch is called viscoelastic stress relaxation.”

Plastic deformation of connective tissue:  Plasticity refers to the permanent elongation of a muscle and its connective tissue. Theoretically, to achieve plasticity, we must stretch our tissue a beyond the limits of it’s elasticity with enough tension and duration to “permanently” deform it.

“The classical model of plastic deformation would require a stretch intensity sufficient to pull connective tissue within the muscle past the elastic limit and into the plastic region of the torque/angle curve so that once the stretching force is removed, the muscle would not return to its original length but would remain permanently in a lengthened state.”

Increased serial sarcomeres: In this theory it is thought that muscles elongate from persistent tension by adding additional sarcomeres to the length of each muscle fiber. Sarcomeres are the basic component of each muscle fiber. They are arranged longitudinally in the cell, like boxcars in a long train. With enough load for a sufficient time, each muscle cell adds more sarcomeres in series. This would be something like a chain under tension adding additional links to lengthen itself to avoid snapping from the tension.

Yoga is a great example of neuromuscular relaxation.
Yoga is a great example of neuromuscular relaxation.

Neuromuscular relaxation: Some researchers have theorized that long slow static stretch “stimulates neuromuscular reflexes that induce relaxation of muscles undergoing static stretch,” and that over time and repeated sessions with this approach, the neuromuscular reflexes adapt to the persistent tension allowing the stretched muscle to relax,  “which enhances the stretched muscles’ ability to relax and results in increased muscle extensibility.”

Sensory theory of extensibility: This theory postulates that it’s really just all in our heads. Well, not exactly, but close enough. Essentially, the sensory theory suggests that the above explanations of anatomical and biological changes are incorrect. Instead, the individual experiencing the stretching is simply able to tolerate the elongation of the tissues with less pain and discomfort. Basically, they become conditioned to the sensation and because they can better tolerate it, they experience more extensibility of their tissues and increased ROM of their joints. This theory is enjoying more widespread support amongst scientists and researchers.


What’s the most effective technique? 

Regardless of how it works, we do know that stretching does improve our flexibility. So then, that begs a few questions… How to do it? What are the most effective techniques? When is it best to stretch? How often? For how long?

Like many areas of fitness, there are various schools of thought and considerable debate surrounding all of these questions. The volume of research and writing on this topic could fill libraries.

A classic static stretch for the hamstrings
A classic static stretch for the hamstrings

Static stretching: is probably the technique that people are most familiar with. It involves statically holding each stretch at the limits of our ROM for a sufficient period of time to induce extensibility. The movements are slow and constant. There is ample research to support that this approach is effective, but it’s necessary to hold the stretch for a sufficient period of time, at least 15 seconds and as much as 30 seconds per hold. Holding a stretch in excess of 60 seconds has been shown to have diminishing returns. Bending to touch our toes could be the most recognized example of a static stretch.

Dynamic stretching: this functional approach involves actively moving the joint through it’s full range of motion while gently but repetitively pushing to the end range of our ROM. This approach is favored by many sports scientists, coaches, and athletes as an effective method to warm up our bodies prior to competition or training. Dynamic stretching can be generic or sport/activity specific. It usually involves functional movements such as deep squats and lunge-like movements. You will often see elite athletes engaged with dynamic stretching during their on-field warm ups prior to competitions.

Dynamic stretching to prepare for a run.
Dynamic stretching to prepare for a run.

Rhythmic or ballistic stretching: with this technique the athlete extends to the limits of ROM and then uses rhythmic bouncing-like movements in which they do not hold the end position. While this approach does have some useful applications for very specific activities, it is largely frowned upon as being dangerous due to increased risk of injury. Ballistic stretching usually triggers what’s known as the stretch reflex. This is the body’s autonomic reaction to a rapid stretch. In essence, the elongated muscle actually contracts to protect itself. There are safe applications of this technique that are sometimes useful as part of a warmup, but in general, it’s best to stay away from this approach except when under the supervision of a trained Strength and Conditioning Coach or Therapist. You might recognize ballistic stretching when you see a dancer doing repetitive rhythmic bouncing stretches as she warms up her legs prior to recital.

Proprioceptive Neuromuscular Facilitation (PNF): this topic is fairly complex, one for which I don’t really have the space to explain adequately in this article. Suffice to say, that PNF is a technique that uses combinations of contraction and relaxation of our muscles in specific sequences while stretching. PNF takes advantage of the stretch reflex and subsequent relaxation to facilitate extensibility. In some respects it is a method that sort of tricks our neuromuscular network to allow the targeted muscle to relax in order to be stretched.

Undulating stretching: this innovative approach involves gentle wave-like movements near the limits of our ROM and timed with deep inhalations and exhalations that gradually overcome the body’s innate resistance to the stretch. This allows the targeted muscle to relax thereby facilitating increased tissue extensibility. Championed by Ann and Chris Frederick from California, this approach has been gaining acceptance through the outstanding anecdotal experience of a great many elite and professional athletes who have become regular practitioners.

Muscle spindles in action responding to the Stretch Reflex
Muscle spindles in action responding to the Stretch Reflex

Most of us have experienced the fairly uncomfortable sensation associated with static stretching. When you are feeling tight and inflexible, it’s not uncommon that your initial response to a static stretch is to actually become rigid and strain to hold or extend the stretch, all the while holding your breath and maybe even gritting your teeth because it hurts. Does that sound familiar? From my own experience, that was exactly how stretching felt to me and was probably the main reason I hated doing it so much. The thing is, our muscles have a built-in protective response to muscle stretch, the stretch reflex, which we’ve mentioned earlier. Specialized muscle fibers known as muscle spindles and Golgi Tendon Organs (GTO) protect our muscles and tissues from stretching too far too fast and the consequent tears or ruptures that might result. When we force a static stretch and try to grit our teeth and bear it, we are often wasting our time. Eventually, if you were capable of holding the static stretch long enough (greater than 15 seconds up to 30 seconds) the targeted muscle might actually relax and you’d gain some extensibility. But, because this feels so uncomfortable, too few will hold the position long enough for it to do any good. When you abandon the stretch too early, you will not get any benefit from the effort. You will have endured all that discomfort for no good reason. Seems like a shame.

Undulating stretching uses the deep rhythmic breathing to convince the targeted muscle to relax thereby bypassing its embedded propensity to protect itself from the potentially damaging effects of elongating. This technique feels much more relaxing and pleasant than some of the others, particularly static stretching. Rather than holding each stretch for a prescribed time, such as 30 seconds, instead undulating stretches are timed with the number and duration of your deep breaths. In some cases, you might “hold” the stretch for three or more deep breaths and each breath might cover 5-15 seconds. It will vary depending on your needs and the specific sensory responses that you’ll receive from the joints and muscles you are targeting. The book Stretch To Win is a highly readable and excellent resource to learn more. I highly recommend it.


When should we stretch? Before, during, or after training?

As with nearly everything associated with this topic, there is contradictory scientific evidence and consequently robust debate. It used to be conventional wisdom that we needed to perform extensive static stretching prior to training. Now however, there is emerging consensus that dynamic stretching techniques may be appropriate in preparation for training while static, PNF, and undulating techniques may be better suited post-training.

My own experience as a life long athlete and Strength Coach is to consistently complete an extensive dynamic stretching routine prior to my training and to utilize a blend of static and undulating stretching as part of my recovery and cool down.

The comprehensive dynamic stretching prior to working out seems to better prepare my body for the rigors of the exercise. How much time and focus I apply to my pre-workout routine will depend on the intensity of the planned exercise. For example, whenever I do complex and challenging lifts with heavy weights, such as deadlifts or power cleans, I work through an extensive dynamic stretching program for as much as 20-30 minutes. These lifts have a much higher risk of injury so the extra time and energy preparing for them helps me to complete the workouts safely and hopefully avoid injury. Conversely, if my planned workout is an easy run, I still religiously go through a battery of preparatory movements, but it’s a bit of and abridged version which doesn’t take as much time.

After training, I try to program a solid 15 minutes for MFR and restorative undulating stretching. Depending on how intense the workout might have been, I may spend as much as 30 minutes with restorative stretching.


How often should I do this? Once a week? Two to three times? 

Again, there is hardly consensus on this topic. Most research would suggest that it’s important to stretch for 15-20 minutes a few times per week. There is also support for more extensive and deliberate time spent working intentionally on flexibility. From my point of view, any consistent and dedicated time devoted to flexibility will be well spent. Whether that’s two or three sessions per week or every day, you will reap flexibility improvements proportional to the time you devote to it.

Because we all live in a real world with limited time and resources, I would suggest that 2-3 short sessions per week, with about 15-20 minutes devoted to flexibility, will help you to feel much less tight and you will begin to feel more flexible. If you can create the time for it, an additional longer session per week in which you focus almost exclusively on flexibility for as much as an hour, will really help you to improve. In such a session, you can complete a full and concentrated MFR session and follow that with a comprehensive stretch from toes to nose. You will thank yourself every time you do this. The sensation at the conclusion of these sessions is much like you feel after a massage. You’ll feel loose and limber and very relaxed. It is most definitely worth the investment of your time. 

Consistent focus on flexibility will measurably improve your athletic performance and how you feel physically and emotionally in your everyday life.
Consistent focus on flexibility will measurably improve your athletic performance and how you feel physically and emotionally in your everyday life.

But why don’t we do this more often???

OK, that all sounds great, right? So, why do so few people work on their flexibility? Why do so many of us feel chronically tight and sore? Well, I believe it’s because of the discomfort associated with traditional static stretching. The average person will do just about anything to avoid pain, even moderate to slight pain. For most people, static stretching simply hurts. Who wants that??? Most of us have too much pain in our lives already, who would voluntarily seek out more?

Of course the irony of this is that regular work and time devoted to flexibility would help us to overcome the temporary discomfort and would do wonders to help us diminish or eliminate the chronic discomfort associated with tightness.

But, I hope that this series of essays may have encouraged you to look at flexibility from a new perspective. I believe that you will find it to be time well spent and that you will thank yourself profusely when you adopt a habitual focus on flexibility.

Be well, and stay loose…

Works Cited:

  1. Barnes, J F. Myofascial Release: A Comprehensive Evaluatory And Treatment Approach. Rehabilitation Services, Inc, 1990. Print.
  2. Enoka RM. Neuromechanics of Human Movement. 3rd ed. Champaign, IL. Human Kinetics Publishers; 2002.
  3. Frederick, Ann & Christopher. Stretch To Win, Flexibility for Improved Speed, Power, and Agility. Champaign, IL:Human Kinetics, 2006. Print.
  4. Gajdosik RL. Passive extensibility of skeletal muscle: review of the literature with clinical implications. Clin Biomech (Bristol, Avon). 2001;16:87–101.
  5. Holzman Weppler, C., Magusson, S P. (2010). Increasing Muscle Extensibility: A Matter of Increasing Length or Modifying Sensation. PHYS THER,90: 438-449.
  6. Myers, Tom. Anatomy Trains, Myofascial Meridians for Manual and Movement Therapists. London: Churchill Livingston, 2014 Third Edition. Print.
  7. Page, P. (2012). Current Concepts In Muscle Stretching For Exercise and Rehabilitation. The International Journal of Sports Physical Therapy, 7 (1): 109-119.
  8. Smith CA. The warm-up procedure: to stretch or not to stretch: a brief review. J Orthop Sports Phys Ther. 1994;19:







Paul Reilly

Paul is the Owner and Founder of MidStrong. He created MidStrong in 2017 to train men and women in midlife who are busy with work and family to build muscle and burn fat so they can look and feel better than they did in their 20’s. MidStrong is making Functional Fitness training safe and fun, and inclusive. He and his wife, Julie also own and operate MidStrong locally, their bricks and mortar business, previously called ACCELERATED Strength & Balance. It is a boutique fitness center specializing in training folks in and around Westborough through the challenges of midlife for more than five years.