Table of Contents

  1. Introduction
  2. Defining mobility and flexibility
  3. Nuances of Movement
  4. Why do our muscles feel 'tight'?
  5. Types of Stretching
  6. Effects of Stretching
    1. Does stretching reduce 'tightness'?
    2. The long-standing debate of stretching science
    3. How much do you need to stretch?
    4. Stretching, to the limit?
    5. Stretching for injury prevention
    6. Stretching for soreness
    7. What about the other types of stretching?
  7. Do the claims hold up?
  8. Is there a better option?
    1.  Article Summary
  9. Flexibility and Health
  10. Conclusion

Introduction

Various myths have been perpetuated by countless fitness and wellness "professionals" on social media, many of whom, have gathered a substantial cult-like following by inventing 'novel approaches' that work to:

  • Improve mobility,
  • Fix posture
  • Reduce injury risk
  • Improve performance and strength
  • Relieve 'tight' areas/muscles/knots

Do these claims hold any truth or are they just fabricating an issue that has no basis in science and reality, only to offer their viewers a resolution, often at a price?

Some classic examples I've heard personally:

  1. "You HAVE to warm up and stretch before working out, or else you'll get injured!"
  2. "You HAVE to stretch a particular way or do a specific "mobility" routine to move well or relieve a tight muscle
  3. "You HAVE to stretch your legs before you run/workout, otherwise you'll get too sore afterward!"

There's a lot to unpack here today, but I'll start by addressing the low-hanging fruit we're all too familiar with:

Stretching; and its various sub-types, passive, dynamic, etc.

If you notice, it lies in the middle of all those claims above.

We've all done some stretching at some point in our lives — before or after a run, sport, strength training, or even throughout an entire activity, like yoga. 

It's also occasionally prescribed by allied healthcare professionals (podiatrists, physiotherapists, occupational therapists) and alternative medicine practitioners (osteopaths, chiropractors, etc) alike.

But herein lies the question.

Why do we do them (or prescribe them)?

For most of us, I'd suspect the reason is amongst the 3 bullet points I alluded to earlier.

But does stretching really accomplish those goals? or is it a complete waste of time? 

Before we even begin discussing about stretching, let's first define common terminologies, such as mobility, and movement (this topic will be discussed in depth in a future article).

I'll then analyze existing data on the physiological effects of stretching, and its sub-types, along with other relevant scientific research, and compare these data with existing narratives to see if they're validated.

Defining Mobility and Flexibility

Before delving into potential interventions to positively affect said terms, it's essential to establish clear definitions for mobility and 'tightness.'

In my daily practice, I evaluate patients' mobility and identify impairments (i.e. poor joint mobility, resulting in a reduced joint range of motion at the joint measured through a goniometer). This reduction in range of motion at a certain joint is multifactorial, it can be caused by joint contractures or underlying soft tissue limitations.

These limitations are often erroneously generalized as 'tightness', or a lack of flexibility. I'll elaborate more on this in the next section.

Flexibility is defined as your muscles and joints' ability to move through the full range of motion, which has long been classified under health-related fitness components (See Figure 1). Besides this, there are skill-related fitness components as well, which we will not be discussing in this article, but it's good to know that they exist (See Figure 2).

Figure 1. Health-Related Fitness Components
Figure 2. Skill-Related Fitness Components

After a physiotherapy assessment, a treatment plan is subsequently formulated, mainly with therapeutic exercise and/or adjunct treatments to address these underlying impairments that may impede a patient's mobility.

In the healthcare setting, mobility typically means having the physical ability necessary to move freely, independently, and purposively around his/her environment.

It follows a continuum from total immobility to frequent travel to distant locations.

Mobility is defined as having the physical ability necessary to move freely, independently, and purposively around his/her environment. It can range from total immobility to frequent travel to distant locations

- Marcus Oon, PT, CSCS

On the other hand, in the realm of fitness and wellness, the concept of mobility is often vague and its definition can differ depending on who you ask. Many individuals use this term to substantiate their own beliefs about non-existent issues.

In my opinion, the observation of mobility is highly subjective, even more so if it is observed by someone who is not trained in mobility assessments, such as gait analysis. 

This means that normal (or abnormal) movement depends on what the observer perceives as normal, which is highly influenced by prior experience or training. 

In my first article, I briefly mentioned that no human being on this planet is perfectly symmetrical or identical on a structural level, even twins. This statement applies to various anatomical structures, including muscles, bones, and organs. 

Given this inter-individual difference in anatomy, why should we expect that movement should 'look' the same for everyone?

Of course, the statement above excludes obvious movement impairments like the hemiplegic gait that is observed in patients after a stroke, but that aside, everything else we observe of human movement is arbitrary at best.

This lack of understanding has perpetuated the term's misuse and led many to chase the 'best' mobility program or routine to achieve 'perfect' athletic performance. This often comes at a heavy price (in time, effort, and money), which can either be spent getting stronger in the gym or doing sport-specific training in the field.

Nuances of movement and how we assess it

How often have you heard of such terms being thrown around — 'poor form', 'poor position', or 'poor movement'?  and most often, these are linked to 'tight' or 'inactive' muscles? (yeah glute amnesia, I'm looking at ya).

Is it simply a matter of movement variability between individuals? or does the observed 'technique' have a measurable impact on performance? For instance, does it hinder the person's ability to do more repetitions, sets, increase weight, or cause fatigue earlier than expected?

Even if the technique 'looks bad', there are also other variables to consider — such as pain,  whether the movement is pain-inhibited, or if the way the exercise is performed is proven to be injurious.

In many cases, acute pain from resistance training can be traced back to exercise dosage and excessive loading. These factors play an outsized role when compared to exercise technique, and it is where, I reckon, more exercise/health professionals should pay attention to. 

The complexity of human movement is often under-appreciated, and because of this, it is:

   1) Seen through a reductionist lens by those who don't have the expertise or knowledge in this area, i.e. claiming that a certain movement causes injury or is bad for you, or that there's a 'perfect' form, posture every human being should adhere to.

  2) Over-complicated by 'gurus' that use abstract terminologies to appear knowledgeable so that you buy their program (does 'postural correction' 'corrective exercise' or 'unlock your true mobility' sound familiar?)

Before we discuss stretching, I'd like to briefly explain the phenomenon of 'tightness' that most of us commonly experience, which leads us to stretch in the first place.

Why do our muscles 'feel tight'?

We've all probably complained of 'feeling stiff' at some point in our lives. However, describing a sensation as 'stiff' or 'tight' lacks precision and is rather subjective. These sensations often hint at minor underlying issues, a sort of mild discomfort—essentially, stiffness is a symptom.

This symptom is widespread, and many are consistently seeking ways to alleviate it. We engage in activities like stretching and contorting during hot yoga sessions, in an attempt to improve our posture, or even visit chiropractors for 'adjustments' or massage therapists for 'releasing'.

In massage therapy sessions, the phrases 'your traps are tight, or your hamstrings are tight' are commonly heard, yet they often lack specific meaning.

Symptoms often have a cause, and in the case of 'tightness', it's unanimously attributed to stiff joints, which more often than not, is not the main cause of feeling stiff. Obviously, no one likes feeling stiff, it's uncomfortable. 

Our results provide compelling evidence that a feeling of back stiffness relates poorly to biomechanical measures of back stiffness. Consistent with our hypothesis, we show that a protective response exists in people who report feeling back pain and stiffness: they overestimate applied force and are better than healthy controls at detecting any change in this force.

Stanton, T. R., Moseley, G. L., Wong, A. Y., & Kawchuk, G. N. (2017). Feeling stiffness in the back: A protective perceptual inference in chronic back pain. Scientific Reports, 7(1). https://doi.org/10.1038/s41598

The authors further add that "the lack of a difference in objective spinal stiffness between those with and without reported stiffness and LBP, is consistent with the idea that our bodily feelings reflect multimodal and evaluative processes, serving as behavioral drivers rather than markers of a biological or biomechanical state". 

Simply put—it means that people without stiffness and those with stiffness had no measurable difference in spinal stiffness, highlighting that our bodily feelings or 'perception of stiffness' are linked to processes in the brain that drive certain behaviors. This challenges the common explanation that stiffness equals something abnormal occurring in our muscles.

Beyond this theoretical explanation, there are numerous reasons why you might experience a sensation of stiffness. Do note that the list below isn't exhaustive, and you might be surprised to learn that only one of these factors is strongly associated with a decrease in joint range of motion.

  • Delayed Onset Muscle Soreness (DOMS) 
  • Overuse injuries like Tendinopathies
  • Arthritis (osteoarthritis, rheumatoid arthritis)
  • Inflammation from autoimmune and infection.
  • Chronic Regional Pain Syndrome (Fibromyalgia)
  • Side effects from certain medications, typically those that affect dopamine or acetylcholine
  • Rigidity (Parkinson's disease)
  • Limb Dystonia (mostly from brain injuries such as a stroke)

Finding out the root cause of stiffness is just as challenging as diagnosing the main contributor to pain, due to its highly subjective nature.

Types of Stretching 

Long gone are the times when static stretching is the only way to perform stretches, where we actively lengthen the muscle by bringing its proximal and distal attachments further and holding it there for a while (usually seconds to minutes). 

When you stretch the muscles, other structures in proximity like the nerves inevitably get stretched too. Clinically, the stretching of nerves is termed neurodynamic stretching.

Moreover, we now possess a range of innovative methods that essentially achieve the same objective. By incorporating subtle contractions or movements in combination, an entirely new realm of stretching emerges - known as dynamic stretching.

Some major sub-types of dynamic stretching include:

  • Proprioceptive Neuromuscular Facilitation or PNF (in various forms)
    • Hold-Relax Stretching (HR)
    • Contract-Relax Stretching (CR)
    • Hold-Relax with Agonist Contraction (HRAC)
  • Dynamic Mobility Drills (i.e. swinging your legs back or swinging your arms in circles)
  • Mixed Stretching 
    • I consider this to encompass all kinds of practices and sports that involve stretching to a certain degree (such as yoga and martial arts)

Let's look at each of them and see if they provide actual physiological benefits at the tissue level and outcomes we actually care about.

Effects of Stretching

Does stretching improve flexibility and reduce 'tightness'?

When I examined several stretching studies in detail, I was amused how something that had close to zero measurable benefits, be implemented so ubiquitously — from competitive sports training, recreational lifting, and running, to military training and everything else in between?

Could I have missed something?

Upon re-examining the studies, I evaluated their quality and limitations. However, it did not alter my interpretation of the data —  that static stretching is essentially a huge time-waster.

That said, stretching does actually increase flexibility,

for what it's worth.

To quote the authors of those studies:

"In conclusion, static stretching was effective in increasing hamstring flexibility in healthy young adults"

Mederios et al. 2002

"Static Stretching and PNF stretching had no clear effect on all-cause or overuse injuries; no data are available for Dynamic Stretching. All forms of training-induced ROM improvements, typically lasting <30 min. Changes may result from acute reductions in muscle and tendon stiffness or from neural adaptations causing an improved stretch tolerance"

Behm et al. 2016

"Stretching interventions with 3- to 8-week duration does not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force. Adaptations to chronic stretching protocols shorter than 8 weeks seem to mostly occur at a sensory level"

Freitas et al. 2018

Even The American College of Sports Medicine (ACSM) emphasizes that flexibility holds significance in athletic performance, such as ballet and gymnastics, as well as in the execution of daily activities.

If you recall, in Figure.1, it stands as a crucial element of overall fitness, alongside body composition, cardiovascular endurance, muscle endurance, and muscle strength. In fact, the ACSM recommendation entails 2–3 days of stretching weekly, involving 2–4 repetitions of various stretches per day.

Personal trainers are certainly on board with this notion. Approximately 80% of American trainers incorporate static stretching into their programs, driven by various reasons, with flexibility being a primary factor.

However, when one attempts to articulate precisely why flexibility carries weight, it's notable how quickly clarity falters. While undeniably beneficial for certain specialized requirements—prized on every contortionist's or yogi's résumé— it doesn't necessarily hold immense value for most athletes.

This extends even to athletes who might seem to require increased flexibility. While the idea of being flexible is alluring, pinpointing specific advantages for the majority can be a challenging task.

The long-standing misconception about stretching

As it turns out, flexibility is far more intricate than rocket science. It involves either plasticity, tolerance, or a blend of both, sparking a long-standing debate.

Do our tissues genuinely elongate, akin to stretching 'play-dough', to enhance flexibility? Or is it a result of our brains adapting to discomfort and essentially "learning" to achieve greater tissue length — a sensory and neurological phenomenon?

Well, let's find out.

How much stretching do you need to achieve significant benefits? 

Back in my undergraduate training, we were taught that therapeutic stretches (mostly passive stretching) had to be held for a duration of at least 30 seconds.

This concept is based on past evidence that 30 seconds is the minimum time needed for the Golgi-tendon organ to exert inhibitory effects on muscle spindles, and hence muscle tension, temporarily increasing flexibility (or improving the range of motion at the joint of interest).

Here's an excerpt from another blog that explains the mechanism well:

When the Golgi tendon organ is excited for a prolonged period of time (at least 30 seconds according to the National Academy of Sports Medicine), it provides an inhibitory effect to muscle spindles, which are trying to contract the muscle.

This means, that when we hold a stretch for long enough, the Golgi tendon organ overrides the muscle spindle activity, causing relation in the overactive muscle, allowing for it to be stretched to its optimal length. 

It takes about 30 seconds for this override to occur, which is why it’s so important to hold stretches for a solid amount of time in order to really stretch out a muscle.

Nourish North West Blog

So if a stretch is to be held for at least thirty seconds, what about how often, and how hard?

In other words, what is the best stretching regimen for optimal flexibility gains? Is five seconds of bouncing up and down reaching for your toes enough? or would it take five minutes, twice a day of intense stretching effort for three months?

Well, my answer to this conundrum is simply:

  • It's difficult to know for sure
  • A reasonable amount would probably suffice
  • Increasing the dosage further than the above would likely have diminishing returns

If you think those are general statements, that's because they are.

It's clearly impossible to state absolutes when the studies we have available on the 'best' dosage for stretching are heterogeneous and inconclusive.

In reality, most people only stretch briefly, probably 5 minutes before and after a run, or dynamic stretches for a few repetitions prior to squatting. Just a cot-tangent here but it's worth mentioning that — the majority of individuals do not even meet the recommended physical activity guidelines, and yet here we're talking about adhering to a rigorous stretching routine, which probably wouldn't turn out well. 

Circling back to the topic, a dated and small comparative study showed that 15 seconds is better than five, but these effects only apply to active, not passive ROM and the gains diminish quickly.

Another randomized controlled trial by Marshall et al in 2011 assessed hamstring extensibility, stiffness, stretch tolerance, and strength in two groups of participants. One group received a 4-week stretching program consisting of 4 hamstring and hip stretches performed 5 times per week, while the control group received no stretching. At the end of the study, the group that stretched improved their range up to 20%.

Not bad.

But what if you're a bit more — overzealous? 

Stretching to the limit: Maximum effort for maximum results?

If you're a martial artist or gymnast reading this post, you've probably done your fair share of stretching during training, be it dynamic, static stretching, or both (mixed), and you've probably injured yourself at some point during your sporting activities (during a sparring match, for example). 

In fact, it may even be necessary for these soft tissue structures — ligaments and capsules, to get traumatized, so you can get them to move further past what was previously achievable.

This is where things get slightly more complicated. If your sport or activity demands require frequent access to controlled, movement at the end ranges of motion for most joints — you need to be able to access and train in those ranges of movement. This is because physiological adaptations are specific to the demands you impose on your body.

Nonetheless, outside of those specific adaptations, flexibility doesn't translate well to other health outcomes (elaborated in detail below), and it often comes at a cost. For example, excessive mobility in an already mobile joint such as the shoulder, may lead to shoulder instability and consequently, injury to the joint capsule and surrounding structures.

Stretching for Injury Prevention

Perhaps a contrarian view, but stretching may actually cause injuries, mainly because many try too hard. Furthermore, stretching does not prevent injury, as shown in randomized clinical trials, literature reviews, and large studies of studies (meta-analyses).

So why is stretching before and after workouts still so ubiquitous across various settings of health and fitness? Could it be due to social desirability, or is it merely a behavioral response? (i.e. the bandwagon effect) For example, stretching because others are doing it and therefore, an assumed benefit to doing so. To quote the authors from the above studies and more..

The pooled estimate from two studies was that stretching decreased the risk of injury by 5%. This effect was statistically non-significant. Even if this effect was not simply a sampling error it would not be large enough to be of practical significance. In army recruits, whose risk of injury in the control condition is high (approximately 20% over the training period of 12 weeks), a 5% reduction in relative risk implies a reduction in absolute risk of about 1%. Thus, on average, about 100 people stretch for 12 weeks to prevent one injury and (if the hazard reduction was constant) the average subject would need to stretch for 23 years to prevent one injury.

Herbert D Rob (2002)  Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ 2002;325:468 

Stretching was not significantly associated with a reduction in total injuries,  and similar findings were seen in the subgroup analyses. However, there is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent injury among competitive or recreational athletes.

Further research, especially well-conducted randomized controlled trials, is urgently needed to determine the proper role of stretching in sports.

THACKER, S. B., GILCHRIST, J., STROUP, D. F., & KIMSEY, C. D. (2004). The impact of stretching on Sports Injury Risk: A systematic review of the literature. Medicine & Science in Sports & Exercise, 36(3), 371–378. https://doi.org/10.1249/01.mss...

Reduction in total injuries (shin splints, tibial stress reaction, sprains/strains, and lower-extremity and -limb injuries) with either stretching of specific leg-muscle groups or multiple muscle groups was not found in 5 controlled studies. Reduction in injuries was not significantly greater for stretching of specific muscles or multiple muscle groups

Hart, L. (2005). Effect of stretching on Sport injury risk: A review. Clinical Journal of Sport Medicine, 15(2), 113. https://doi.org/10.1097/01.jsm...

These studies were published almost 2 decades ago, and already, stretching as prevention for injury looked rather bleak and had poor clinical utility. Let's further examine if this preliminary evidence has been confirmed by recent studies.

In 2008, a systematic review published in the journal, Research of Sports Medicine investigated whether static stretching before exercise reduced overall injury rates, and their conclusion was that "There is moderate to strong evidence that routine application of static stretching does not reduce overall injury rates".

In a 2014 review published in the British Journal of Sports Medicine, the outlook for stretching was rather grim, to say the least. The review, while somewhat optimistic about various other aspects, painted a completely negative picture of stretching concerning injury prevention. The authors concluded, "Consistently favorable estimates were obtained for all injury prevention measures except for stretching." Ouch indeed.

What about stretching specifically for runners? Surely static stretching helps to prevent running-related injuries?

Well..let's have a look at the data.

When it comes to the practice of stretching before a run — a large prospective study conducted by researchers at Simon Fraser University stands out. It's an impressively extensive study, encompassing over 2700 participants. Their findings? "no statistically significant difference in injury risk between the pre-run stretching and non-stretching groups." 

This point is further supported by a 2017 review that stretching isn't useful for runners or endurance athletes of any level in preventing running-related injuries. In fact — it may even be counterintuitive!  (According to the authors, "Acute stretching can reduce running economy and performance for up to an hour by diminishing the musculotendinous stiffness and elastic energy
potential.").

and finally, in 2020, the British Journal of Sports Medicine published an infographic  — that essentially declared that stretching is of no value for injury prevention and performance. The only recommended use for stretching at all, according to the authors, is that it "may assist the runner to relax after a run".

I'm not particularly surprised by these findings, since I have yet to come across an elaborate, logical explanation by an appropriately credentialled expert as to how stretching mechanistically helps to prevent injuries since we know that the typical stretching performed by many lacks in intensity and frequency. Furthermore, these changes in musculotendinous stiffness and tension are transient, with resting tension and length restored as quickly as 30 minutes after stretching.

Nevertheless, in May 2023, a narrative review of 17 studies published in Sports Medicine found that Dynamic Stretching (where dynamic movements such as shoulder rotation, trunk rotation, hip flexion, extension, abduction or adduction, high knee lifts, and other movements through a full ROM under control) combined with dynamic activity (jumping, landing and running) helped to reduce injury incidence rates in amateur to elite soccer players by a significant amount. There were some limitations to the included studies.

First, this review examined dynamic stretching with dynamic activity (mainly the FIFA 11+ warm-up program), not static stretching. Second, the included studies had these players warm up for 25 minutes at a time, 2x-3x per week for a total duration of 3 to 9 months. It's unlikely any of us normies will stick to a stretching routine for that long.

To wrap up this section, injury rates for all types of injuries remained consistent, whether static stretching was performed or not. It's almost as if stretching had no impact whatsoever. Dynamic stretching with activities prior to sport does show some promise, in soccer players. 

The final judgment is yours to make! I will be monitoring the evidence in this space, and if anything changes, this section of the article will be updated to reflect that accordingly.

Stretching for soreness

The most common type of soreness following a workout is termed DOMS, or delayed onset muscle soreness that peaks roughly 24-48 hours post-exercise. 

It has been suggested to occur due to an increase in cellular metabolites (accumulation of hydrogen ions associated with lactic acid during strenuous exercise) in the muscle and surrounding tissues following unaccustomed strenuous exercise (particularly if a large amount of that work was eccentric contractions, where the muscle lengthens/stretched). 

It also ranges widely in severity, from mild soreness that dissipates the day after, to extreme soreness that persists up to 7 days. Also, it's important to point out that the duration of soreness and intensity is highly dependent on the intensity and duration of the exercise performed.

Many are of the belief that stretching helps to reduce this post-exercise soreness. However, this belief has been proven false by multiplewell-designed studies in reputable journals. Whatever stretching does (or does not), has no effect on DOMS at all.

What about other types of stretching? 

Now you must be asking, what about PNF? Is PNF any different in terms of flexibility outcomes compared to static stretching?

Does it provide superior benefits?

After all, many personal trainers and alternative health practitioners swear by it.

To be brutally honest, the contract-relax version only adds contraction, and according to multiple studies, it doesn't have any benefits over regular static stretching, although I'd reckon it does add some variation to static stretching, which can get boring.

Some people just like a little more 'discomfort', I guess?

To quote the authors' findings:

"This review concluded that there were 'consistent findings from multiple low-quality studies indicating no difference when comparing proprioceptive neuromuscular facilitation [contract-relax] stretching programs to static stretching programs.' While the evidence is limited, if there is any discernible signal in this data, it appears to be quite weak. It's worth noting that the studies reviewed are likely produced by individuals biased in favor of PNF, yet even with this potential bias, they still found no significant difference."

Hill KJ, Robinson KP, Cuchna JW, Hoch MC (2017) Immediate Effects of Proprioceptive Neuromuscular Facilitation Stretching Programs Compared With Passive Stretching Programs for Hamstring Flexibility: A Critically Appraised Topic. J Sport Rehabil. 2017 Nov;26(6):567–572.

"PNF stretching was not demonstrated to be more effective at increasing hamstring extensibility compared to static stretching. The literature reviewed suggests both are effective methods for increasing hip-flexion ROM. Strength of Recommendation: Using level 2 evidence and higher, the results show both static and PNF stretching effectively increase ROM; however, one does not appear to be more effective than the other"

Lempke L, Wilkinson R, Murray C, Stanek J. The Effectiveness of PNF Versus Static Stretching on Increasing Hip-Flexion Range of Motion. J Sport Rehabil. 2018 May;27(3):289–294. 

The hypothesis that PNF stretching could have an advantage over SS was not confirmed in our investigation. Both the meta-analysis and the individual study level analysis showed that SS and PNF seem to be equally effective in enhancing hamstring flexibility both chronically and acutely

There is a considerable amount of evidence stating
that the increase in flexibility after short-term stretching
seems to be related to an increased tolerance to stretch
(increase in passive torque at end range) rather than a
decrease in musculo-tendinous stiffness. It has been observed that PNF increases stretch tolerance more than static stretching

Borges, M. O., Medeiros, D. M., Minotto, B. B., & Lima, C. S. (2017). Comparison between static stretching and proprioceptive neuromuscular facilitation on hamstring flexibility: systematic review and meta-analysis. European Journal of Physiotherapy, 20(1), 12–19. 

Despite its grandiose name, perhaps it's not that different from static stretching in terms of the health and performance outcomes we're looking for.

Do the claims about stretching hold up?

Recent advancements in muscle physiology have unveiled the concepts of stretching 'muscle length tests' to fall short (By the way, that paper is a must-read for those who are serious about treating and providing evidence-based information to your patients/clients).

Essentially, the authors also state that current muscle length tests in clinical practice are one-dimensional and consist of just measurements of end-range joint angles. They do not capture the multidimensional nature of muscle length such as tension, cross-sectional area, and time.

For stretching, studies show that although there is indeed an inhibitory effect on muscle tension, the outcomes are only transient, after which the muscle-tendon unit typically returns to its original resting tone and length.

And..Read those two paragraphs again.

If you can't remember what I've written on this topic so far, or you just think it's all useless information, all I ask is to remember the two paragraphs above and share that with your gym buddies (or yoga buddies).

I myself, share this with people who still hang on to outdated concepts, whenever I can*

*One of the few reasons for starting this blog, it's so damn hard to change peoples' minds especially if it's being perpetuated by the media and countless others, so if you like what I write, do share this article on your social media, The link to do so will be at the bottom of the article.

This was partly due to my ignorance as a first-year student — you don't typically scrutinize things when you have a respected professor advocating for passive stretching as a valuable therapeutic 'modality'.

If he says it's good, who am I to say it's useless?

In retrospect, I think the better question to ask was  'Should you need to stretch?', and I'm not alone on this, especially when 'lack of time' is often touted as the sole reason for not exercising, in adolescents and adults alike.

Is there a better option?

Indeed, strength training has shown to be as effective in enhancing flexibility, while providing superior health benefits in the process.

Surprisingly, compelling evidence in the literature was lacking until a recent paper from 2020 in the Journal of Sports Medicine raised questions about the effectiveness of stretch training and its purported physiological advantages.

To quote the author: 

"Flexibility has been researched for over 100 years. Its track record is unimpressive, particularly when viewed in light of other components of physical fitness. Flexibility lacks predictive and concurrent validity value with meaningful health and performance outcomes. Consequently, it should be retired as a major component of fitness. Because the fundamental purpose of stretching is to improve flexibility, the case for retiring flexibility is also the case for a decreased emphasis on stretching as a standard or necessary component of exercise prescriptions for most populations."

- James L Nuzzo, PhD

Quick Summary of the Article 

The author concluded that specific stretch training should be de-emphasized, further adding that it should be demoted to a secondary component of fitness, since that time could be reallocated to other modes of exercise, such as resistance /aerobic training, which confer superior health and performance benefits.

It enhances flexibility (temporarily) primarily by raising sensory/stretch tolerance (which was mechanistically investigated and discussed in a previous randomized clinical trial) rather than altering tissue structure. However, pursuing flexibility is overrated and can be achieved more effectively through exercises that benefit overall fitness, such as end-range strengthening with load.

No other substantial advantages of stretching have been conclusively demonstrated, regardless of the method used. Many anticipated benefits simply don't hold up: stretching doesn't effectively warm-up, prevent soreness or injury, significantly aid rehabilitation, or enhance performance. In fact, it can lead to injury and hinder performance, albeit not extensively.

In addition to questions about efficacy, stretching is inefficient, and there's an ongoing debate about the "correct" technique. Certain key muscles are bio-mechanically resistant to stretching, like most of the quadriceps group, which runners often struggle to believe without visual aids.

Despite its pleasurable sensation, stretching doesn't seem to serve as a treatment for common aches and pains. This is particularly noticeable when expectations are high, as it doesn't prove to be an effective therapy for back pain, since any exercise intervention works just as well

If that's not convincing enough, a comprehensive 2010 article published in the Physical Therapy & Rehabilitation Journal concluded that

"The biomechanical effect of stretching showed that muscle length does increase during stretch application due to the viscoelastic properties of muscle. However, this length increase is transient, its magnitude and duration being dependent upon the duration and type of stretching applied.

Most of these studies suggest that increases in muscle extensibility observed after a single stretching session and after short-term (3- to 8-week) stretching programs are due to modified sensation and not muscle length."

Weppler, C. H., & Magnusson, S. P. (2010). Increasing muscle extensibility: A matter of increasing length or modifying sensation? Physical Therapy, 90(3), 438–449. https://doi.org/10.2522/ptj.20...

In other words, observed improvements in 'muscle length' in previous studies are likely due to psychological alteration in sensory perception (meaning your brain perceives the feelings of stretch differently), thus increasing your ability to tolerate greater force (or more correctly —  torque) being applied to the joint and muscle being examined. 

Furthermore, the authors added that the usual way of measuring muscle extensibility (defined as the ability of a muscle to be stretched without tearing) via 'muscle length' tests is insufficient as they do not capture the entire bio-mechanical properties of muscular tissue.

Nevertheless, the authors recognized that the longer-term effects on muscle extensibility of stretching regimens lasting more than 8 weeks had not yet been evaluated.  Notably, this study was conducted 10 years ago, whereas the first article that I quoted previously was conducted in 2020. Despite the apparent time gap, both arrived at the same conclusion — that stretching to increase muscle extensibility is at best, minimally significant and at worse, a futile effort.

Therefore, changes in your range of motion may be due to natural biological variation, some people are innately more flexible than others, and pushing at the end of the range is a neutral sensation — it doesn’t feel like there’s a problem, and therefore it is not “stiff.” It’s more just a sensation of being stopped, or of pulling too hard.

Flexibility and Health

In my opinion, more time could be spent on training for outcomes that matter in the shortest time possible, especially if you're the average adult with a day job, kids/older parents to care for, and still want a decent social life.

For many people, including myself, the main purpose of training/exercising is to improve health outcomes, meaning you want to live longer and function better, even at age 80. To do that, we need to keep our lipid profile, blood glucose, and body composition in check, period. Age-associated physical decline is not a myth.

"When individuals possess good aerobic capacity—meaning they're fit enough to efficiently distribute oxygen to all their cells—they tend to be more functional and healthier in various aspects. If stretching were a crucial component of fitness, it should logically be linked to numerous health benefits.

However, this is not the case. Stretching shows minimal impact on any health or functional metrics. More flexible individuals don't necessarily experience reduced mortality rates or fewer age-related falls. Their quality of life isn't significantly higher, and there's little evidence to support this. Moreover, increased flexibility doesn't translate to lower instances of back pain or injuries; in some cases, it might even lead to more issues. Flexibility has minimal bearing on vital health indicators like blood pressure, resting heart rate, and cholesterol levels, which are more closely associated with factors like body weight and endurance.

Additionally, flexibility doesn't correlate with other components of fitness. Flexible individuals don't demonstrate greater strength, endurance, or agility.

As James Nuzzo puts it, "The absence of correlations between flexibility and other fitness components indicates that flexibility is a distinct trait, but not a particularly critical one for health and functionality."

It ultimately comes down to extending our years of vitality into the final decade of life. It means retaining the ability to walk and engage in purposeful activities while avoiding the burden of numerous medications.

This concept has gained significant attention amongst longevity circles lately, and is often referred to as 'health-span'.

To slow down its deleterious effects, we need to be strategic with our training, and flexibility training, unfortunately, does not confer any significant health benefits as strength training or cardiovascular exercise to achieve the health outcomes that truly matter.

Conclusion

The long and short of it is that unless you enjoy the feeling of stretching, I wouldn't go the extra mile incorporating a 15-minute stretching warm-up and cool down prior to any habitual exercise routine or even think about a daily 30-minute stretching ritual. It does not provide any more benefits than say, a back scratch. You'd be better off focusing your time on aerobic exercise or strength training to improve various health metrics (like VO2 max, muscle strength, and mass) that have been shown to correlate well with health trajectory.

P.S. In the next article, I'll be writing about foam rolling (with the commonly seen cylindrical PVC pipe) stay tuned!

Full of bumps and ridges, but do they work?

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Marcus Oon

Marcus is a practicing physiotherapist and strength & conditioning specialist located in Singapore. He completed his Undergraduate (Hons) degree at the Singapore Institute Of Technology - Trinity College Dublin, and his Strength & Conditioning certification at the National Strength & Conditioning Association (NSCA). He is also active in the NSCA's Health and Wellness, Powerlifting, and Sports Medicine/Rehabilitation Special Interest Groups.

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