To Stretch or not to Stretch?

For many years now, stretching has been a popular practice, both within and outside the sporting world (Babault & al, 2021; Spense, Helms & McGuigan, 2022). The proposed benefits are plentiful: increased flexibility, reduced risk of injury, improved performance and facilitated recovery. And yet, when it comes to scientific studies, current data paint a rather different picture. So, what’s the truth?

Introduction

Before getting started, it’s important to understand the difference between flexibility and mobility:

– Flexibility: the ability of a muscle or muscle group to stretch passively through a range of motion, i.e. the passive range of motion of a muscle or muscle group (and associated connective tissues)

– Mobility: the ability of a joint to move actively through a range of motion, i.e. the active range of motion of a joint. Flexibility is a component of mobility, complemented by strength and motor control.

Having a certain range of motion passively (obtained via an external aid) is no guarantee of having the same range of motion under more dynamic conditions.

Next, we need to differentiate between 2 types of stiffness:

– Physiological stiffness, which corresponds to the stiffness of tissues (muscles, tendons, ligaments…),

– Functional stiffness, which refers to the nervous system’s ability to activate muscles to resist dynamic deformation/stretching – think of landing after a jump, for instance. This stiffness is essential for performance and limiting the risk of injury.

Once these distinctions have been made, we can move on to the next step.

How much flexibility do we need?

Firstly, mobility is better than flexibility. Secondly, the « amount » of mobility required is specific to each individual: you need enough to be able to carry out any activity of daily living without discomfort, and enough to be efficient in the sporting activity you practice, while still being able to reach the necessary positions without feeling discomfort. It could even be argued that aiming for a little more mobility than that might be worthwhile, in order to have a « safety zone« .

From an athletic standpoint, a high degree of mobility in traditional bodybuilding movements isn’t essential for resilience – watch the way LeBron James, one of the greatest athletes in history, performs a squat. What’s important for an athlete is movement capacity on the court/field, including the ability to rotate the hips in specific sporting positions.

Along the same lines, according to American NBA trainer Paul J. Fabritz in a recent post on social networks, a lack of flexibility doesn’t prevent from « playing low » in basketball; on the contrary, according to him, several NBA players he’s worked with manage to be effective when playing « low » regardless of limited flexibility. This is also in line with the recent comments of athlete DeMar DeRozan, who claims to have very little ankle range of motion (below certain scientific standards) – which doesn’t prevent him from performing well and missing few games, despite a very busy schedule in the NBA.

What happens when we stretch?

Functional stiffness is important for resisting deformation: muscles create stiffness to allow other elements (tendons, fascia…) to be stretched and store elastic energy. Without this, performance is impaired and the risk of injury increases.

When we perform a static stretch, i.e. when we simply hold a stretching position for some time, the traditional intention is to « lengthen a muscle » in order to « reduce its stiffness » (physiological here).

However, when we stretch a muscle in this way, we activate the myotatic reflex, which in turn contracts the muscle. Its effect is protective because in dynamic situations, when a muscle is stretched rapidly (think of the quadriceps muscles during the lowering phase of a jump), this reflex increases muscle tension and force production to resist deformation/stretching and thus prevent the muscle from « tearing ».

If we do too much static stretching, we can potentially alter the muscle length-tension relationship, i.e. we can change the muscle « length » at which the body is capable of producing maximum force.

This relationship needs to be specific to athletic efforts (running, change of direction, jumps…) to maximize performance but also to minimize the risk of injury, as it’s in this same range of motion – relatively small for most explosive efforts – that this risk is particularly present.

With too much static stretching, you increase the muscle length at which you’re able to produce maximum force, the myotatic reflex takes longer to turn on and tendons end up more stretched than usual, which can be somewhat dangerous. Furthermore, the greater the range of motion, the more difficult it is physiologically to generate force.

Science also teaches us something else: when the myotatic reflex is triggered and causes the contraction of a stretched muscle, it produces a simultaneous relaxation of the antagonist muscle – i.e. the opposite muscle (e.g. the hamstrings are antagonistic to the quadriceps) – according to the law of reciprocal inhibition.

Despite this, static stretching can indeed increase range of motion and relieve some tension. However, the effects are only temporary, as mobility is not increased, only flexibility is; and the root causes of stiffness are not addressed. In addition, gains don’t result from an increase in muscle length, but rather from altered sensation (Weppler & Magnusson, 2010). At the same time, holding the position puts tension on all connective tissues (tendons, fascia, ligaments, nerves…), which isn’t necessarily desirable.

Stretching to prepare for performance and reduce the risk of injury?

If we’re talking about static stretching, the answer is unequivocally no. On the contrary, they can even reduce physical capacity and increase the risk of injury in the short term, via a reduction in muscle activation (Kazemi & al, 2021; Blazevich & al, 2018; Montalvo & Dorgo, 2019).

So if you ever feel an absolute need to do static stretching before a workout, you need to follow it up with dynamic stretching* or movements involving the muscles and joints that are going to be used during the following exertion.

*Dynamic stretching involves an active movement in which muscles and joints move rapidly through a full range of motion

Alternatively, you can start your warm-up directly with dynamic activities: mobility exercises, muscle strengthening exercises, or the same types of movement as those in the sports activity you’ll be undertaking next by gradually increasing the intensity. Whichever modality you choose, the goal is for you to feel good and be ready to kick off your session in the best possible way.

How to gain mobility?

Scientific literature (Moscao Vilaça-Alves & Afonso, 2020) indicates that active methods are preferable to passive ones, with muscle strengthening being the key tool. When performing controlled movements or holding positions with muscle tension in full range of motion, we stretch the muscle while voluntarily producing force.

Examples of positions combining mobility & strengthening

The creation of control and strength in large ranges also reduces the risk of injury, as muscles become more resistant in less advantageous positions. However, in order to maintain an optimal length-tension relationship, it’s essential to balance this type of work with dynamic efforts involving smaller ranges.

The purpose isn’t to achieve as much mobility as possible, but to have « enough »; the right balance must be struck between stiffness (both physiological and functional) and mobility. If you don’t feel any stiffness in your daily life or in your sporting activities, doing a few exercises a week with a full range of motion may be enough to keep you healthy. Mobility can even be worked on through certain sporting actions, by going further and further in the range of motion (while dribbling a basketball, for example).

The FRC Institute offers interesting ideas for working on mobility through strength training with isolated joint movements, notably via Controlled Articular Rotations (active, slow & controlled rotational movements).

In the case of physiological stiffness, it’s possible to perform PNF (Proprioceptive Neuromuscular Facilitation) stretches, using the law of reciprocal inhibition by alternating phases of contraction and relaxation in an ‘’elongated’’ position of a targeted muscle to increase its flexibility. You can also add a contraction of the antagonist muscle in the process.

But to maintain the gains and transform the flexibility into mobility, it’s still necessary to follow this up with dynamic exercises involving the range of motion gained. Otherwise, as with static stretching, performance can be reduced and the risk of injury increased.

Another simple solution for stiffness (based on the law of reciprocal inhibition) is to contract the opposite muscle to the one felt stiff in a position of short muscle length. For instance, in the case of calf stiffness, you can get a loosening effect by raising the front of the feet and the toes as much as possible while keeping the heel on the ground (from a standing or a sitting position).

Stretching to recover?

Well… yes and no. Numerous studies (Pooley & al, 2017; Pooley & al, 2020; Callega-Gonzalez & al, 2021; Afonso & al, 2021) show no beneficial effect of stretching on muscle soreness – whether performed before or after exercise – in contrast to other methods such as active recovery, immersion in water (cold or not) or massage. Stretching can even increase muscle soreness, if the intensity and/or volume aren’t carefully controlled.

But some people still feel some benefits with stretching after a workout, either through a placebo effect or simply by reducing the activity of the sympathetic nervous system (the part of the nervous system linked to stress).

We can also switch the dominance of the nervous system from the sympathetic (stress) to the parasympathetic side (relaxation & digestion) by using another tool: breathing. Adopting a certain breathing routine after exercise can speed up the recovery process and improve learning (Buch & al, 2021; Bonstrup & al, 2019).

Ideally, you should :

• Sit in silence with your eyes closed,
• Breathe only through your nose (this makes better use of the diaphragm, filters and humidifies the air before it enters the system, and improves oxygen transport via nitric oxide production and the Bohr effect),
• Ensure that every exhale lasts at least 4-5 seconds, and is of the same length or longer than the inhale,
• Try to relax your body completely,
• Inflate the belly and ribcage equally, aiming for a 360° expansion of both (this can help gain mobility, according to the work of Postural Restoration Institute).

Learning to breathe through the nose all day long can also help to better manage stress, reduce muscle tension, improve blood circulation (via tissue vasodilation, linked to greater parasympathetic activity) and concentration (leading to better learning and decision-making).

Anatomical aspect of mobility

Several factors influence the potential for mobility:

– Genetics – such as the ACTN3 and COL5A1 genes, or the ability to resist stretching,

– Gender – women tend to be more flexible than men, due to less « resistant » tendons and ligaments (a phenomenon linked to estrogen levels), hence the increased risk of ligament injury for women (stiffer ligaments are better for limiting this)*,

– Anatomical structure, i.e. the way bones and joints are organized (a set of things you can’t change),

– The position of certain elements, such as the pelvis or rib cage.

*This point highlights the idea that we should perhaps be even more cautious when practicing stretching with female populations.

If flexibility is limited by anatomical structure (bone organization, tendon length…), then forcing static stretches with the aim of going further into the range of motion can damage body structures.

Via Conor Harris

For instance, if we pull too hard on a tendon, this will become problematic because during muscle contraction, the muscle pulls on a tendon, which pulls on the bone to produce movement. If the tendon isn’t rigid enough when times arrives, the transfer of force to the bone isn’t efficient. Moreover, pulling too hard on certain tendons (e.g. the patellar or Achilles) can lead to pain symptoms.

Initially, a feeling of stiffness may be due to an alignment problem or a poor positioning of some joints. For example, if the pelvis is tilted too far forward, the hip flexors (at the front of the pelvis) are in a « shortened » position, while the hamstrings (at the back of the thighs) are in a « lengthened » position (see above).

In this scenario, you may feel stiff at the front of the hip because the hip flexor muscles lack strength (for a number of reasons), and at the back of the thigh because the hamstrings are stretched. Here, stretching doesn’t solve the problem, it can even make it worse: if you stretch the hamstrings when they’re already in a « elongated » position, you only increase the instability of the pelvis.

A solution proposed by Postural Restoration Institute is to try to bring back the pelvis to a more neutral state by reducing its forward tilt. To achieve this, they use exercises involving the hamstrings, adductors and deep abdominal muscles to bring the pelvis a little further back.

In the meantime, this type of exercise can help reduce tension in the lower back and improve movement quality. If you still feel the need, you can stretch AFTER this type of work. But if your pelvis is in a good position and/or you don’t necessarily feel any stiffness, stretching isn’t mandatory.

Another mobility test commonly found in sports is the ankle dorsiflexion test (see below). Limited mobility may be due to excessive tension in the calves or shin muscles, or it may simply be the result of anatomical features (such as a structurally « short » Achilles tendon). Simply stretching the calf is therefore not necessarily the right solution, and can lead to pain in the sole of the foot or the Achilles if too much force is applied.

In the ankle dorsiflexion test, the goal is to bring the knee as far forward over the toes as possible while keeping the heel on the ground

To achieve optimum ankle mobility, several strategies are to be considered:

– Performing calf strengthening exercises in full range (or in a range that doesn’t cause pain), with extended knees or flexed legs in order to target different calf muscles,

– Doing strengthening exercises on the forefoot, without the heel touching the ground (floating heel concept),

– Strengthening the muscles of the feet – this increases their stability, enabling them to better express their mobility,

– Spending time barefoot, to awaken the sensory sensors present on the plantar surface, enabling the brain to better sense the arches of the foot.

Neurological aspect of mobility

Let’s move on to the most interesting element in my opinion, the one responsible for muscle tone and stiffness levels: the brain (and the nervous system). If there’s one thing I’ve learned from the various courses I’ve taken in the fields of neurology and kinesiology (RPR, Square 1 System, Z Health, S10 Fitness, Kinesiology Institute), it’s that mobility, strength and pain are byproducts of the nervous system.

In fact, for every movement we want to make, and for every position we want to adopt, the brain starts by assessing the level of « danger » of that action or position. This assessment is based on the interpretation of information coming from 3 systems:

– The vestibular system, in the inner ear, responsible for balance and orientation of the body & head in relation to gravity. The position of the head can have a direct influence on mobility and strength,

– The visual system, including the eyes, optic nerves and brain cortexes, whose role is to transmit information about light to the brain. Gaze direction and eye movements can also have a direct influence on mobility and strength (notably via the oculomotor reflex),

– The proprioceptive system, which refers to awareness of the position of the body and its limbs through various receptors (mechanoreceptors, baroreceptors, thermoreceptors, nociceptors, chemoreceptors, electromagnetic receptors…).

Limited mobility and stiffness sensation result from the nervous system’s perception of a « threat » to (at least) one muscle or joint. This « threat » can be a lack of strength, an old injury, an unusual or uncomfortable position, or even more generalized stress (or something else).

Emotions plays an important role in overall muscle tone, and therefore in mobility. To minimize stiffness and optimize the body’s performance, we need to learn how to manage stress and emotions.

When we consider the neurological aspect of mobility, we understand that all forms of training have an impact on the brain and the nervous system. Static stretching is no exception: initially, when we start to move the body into stretching positions, the range of motion is limited because the brain is unfamiliar with those positions.

In return, it activates reflexes (such as the myotatic reflex) to protect itself against this stretching, which it perceives as a « threat » to the integrity of muscles and joints. Over time, if we continue to adopt these positions, the brain becomes accustomed to them, stiffness decreases and range increases, to the detriment of some essential reflexes.

We can also legitimately wonder about the transfer of flexibility between the positions in which we perform static stretching, and the movements in which we want this flexibility to be expressed – given that the brain only adapts specifically to the positions in which we stretch.

On the other hand, with muscle strengthening, we gain mobility, not just flexibility, and improvements are faster & more lasting. When we hold a position at the end range with a load, the nervous system produces a certain level of force, which can make the brain feel more « secure » and, in turn, it can give access to a greater range of motion.

Without this aspect of strength and control, absent in most stretching conditions, the brain has no reason to feel « secure ».

In this video, you can see a progressive gain in range of motion due to the combination of motor control and nasal breathing

Furthermore, static stretching causes connective tissue to stretch, whereas we want ligaments to remain relatively stiff to limit the space between bones. When this is the case, and there is a certain level of compression in a joint, the ligaments can provide the nervous system with a great deal of information about the pressure level in that joint.

If we reduce the amount of information by over-stretching, we get less tension to protect the joint, which thus becomes less resistant to the stresses encountered in sports and everyday life.

How to get rid of the root causes of an excessive stiffness?

Going back a few paragraphs, a solution emerges: if we can manipulate the vestibular, visual and/or proprioceptive systems appropriately, then we can alter the brain’s perception of « danger », thereby restoring strength and mobility.

This require some knowledge about neurology and/or kinesiology, in order to identify the origins of stiffness/tension. Using the appropriate techniques, it’s then possible to get rid of it very quickly (sometimes in just a matter of seconds).

To Conclude

If you enjoy stretching and feel benefits from it, then don’t deprive yourself. Just be cautious about modalities, overall volume and intensity when you stretch.

If you don’t like stretching and you’re not getting any positive effects from it, then I hope that I’ve shown you some intriguing things to try. The ultimate goal should be to be able to do all the activities you want while feeling good.

So remember to move often during the day, avoid sitting in the same position for too long, and try to mobilize all your limbs regularly.

Friends and fellow fitness trainers, sports coaches and trainers, I now have a few questions for you:

– Are the conditions under which mobility tests are traditionally performed the most optimal for observing the body’s full potential?

– Is static mobility equivalent to dynamic mobility during effort? Wouldn’t some ranges of motion be accessible only with a certain amount of force or impulse?

For instance, standing with legs straight, with one hand against a wall or with something to balance yourself, try to slowly bring the heel of one of your feet as close as possible to your buttocks. Then, with the same foot, try to quickly kick your heel into your buttocks. Is the range of motion the same?

– Aren’t (static) stretching ultimately a waste of time and energy? Two crucial things in the life of an athlete, which we could perhaps allocate to more effective methods/tools for performance and injury prevention?

– Do athletes we work with like to stretch? If not, does it really matter if they don’t stretch?

– Are we sure of the effects of stretching? Should we continue to do it because it’s ingrained in our lifestyles, or should we rethink their use in the light of the elements presented throughout this article?

– Ultimately, is stretching really an absolute necessity?

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