I can only recall 2 situations where my lack of flexibility has limited me (I’m not a very flexible person). The first time was during a game of twister, where I couldn’t quite reach my foot over to the blue circle. The second occasion was when I went bouldering and I was unable to lift my leg high enough to reach the foothold.

Now if I was a keen climber, I would work on improving my flexibility, in order to complete the harder routes. The same goes for if I was a competitive twister player. As it is, my passion is playing football and working out in the gym. I have no problems performing these with my current level of flexibility. I also have no difficulty performing any other activity of daily life.

The reason why I am discussing this, is that most of the population, especially the high proportion who are not involved in any form of physical activity or sport, do not need to be more flexible.

Flexibility is classified by the American College of Sports Medicine (ACSM) as a major component of physical fitness (ACSM 2017). It has also previously been associated with increased injury risk, risk of falls in the elderly and along with posture, a predictor of pain (Corbin and Noble 2013). The continued use of stretches appears to be due to its positive effects on flexibility.

The view is changing though. In 2012, the Institute of Medicine (IOM) recommended tests of flexibility not be included in youth fitness testing. This is due to the lack of evidence for an association between flexibility tests and health outcomes (IOM 2012). Nuzzo (2019) also highlights that decreased flexibility does not correlate to an increased injury risk, based on 8 studies.

O’Sullivan et al (2012) suggest that an altered length-tension curve, and not just reduced flexibility, is what may increase injury risk.  This is secondary to an inability of the muscle to produce adequate force in a lengthened position, exposing the muscle to damaging lengthening forces. Interestingly, stretching does not seem to positively influence length-tension relationships in the same fashion as eccentric training, which improves the ability of a muscle to produce force in a lengthened position.

Recent studies have also demonstrated a poor correlation between posture and pain (Andias and Silva 2019). This indicates that it may not be because certain muscles are tight/inflexible that we are in pain.

Although flexibility has been seen to correlate with worse outcomes in older patients, including falls risk, so has muscle strength. Nuzzo (2019) suggests that it is the lack of strength, rather than flexibility that appears to be the major contributing factor. Even so, by prescribing eccentrics and not stretching, strength will improve as well as flexibility.

The exception to this would be certain sports such as dancing and gymnastics. These sports require a high level of flexibility to perform certain moves. It has however been observed that high levels of flexibility might increase injury risk. In dancers, increased lower-limb range of motion either increases injury risk or does not correlate with injury (Kenny et al 2015) – stretching may therefore increase the risk, but eccentric loading will improve the strength in the improved range, reducing that risk.

To conclude, it appears that flexibility is not as important as previously believed. However, there are a few situations where it may be beneficial, such as in certain sports. Flexibility should therefore be focused on function, as with most physiotherapy interventions. It also seems sensible to conclude that in these situations, an increase in strength and therefore a decrease in injury risk would be beneficial.

If stretching only improves flexibility, but flexibility is only required in situations where muscle strength is also important, then eccentric loading might well be the answer. Since working on this blog, my practice has definitely changed. I now very rarely give out stretches and when I do feel that more flexibility is required, I will prescribe eccentric loading.

This is not to say that stretching should never be used again. People can enjoy stretching and there is not enough evidence to suggest that it is harmful. Therefore, if someone wants to stretch, then they should stretch.

Based on Douglas et al (2017) systematic review of eccentric training, the eccentric exercise should be performed with relatively heavy weights. Studies directly comparing heavier with lighter eccentric loads found that heavier eccentric training induced greater increases in eccentric strength and hypertrophy. If the load is greater than what can be lifted concentrically, then there is an enhancement in muscle mechanical function and adaptation.

I therefore ask my patients to perform 3xsets of 4-6 slow repetitions, ensuring it is taken through as much range as comfortable. The aim is for the muscles to fatigue by the end of the repetitions with 2 minutes rest between sets (Brukner and Khan 2018). However, moving forwards I would like to see more research establishing what dosage is the best.

Patients should then wait until they are no longer sore before performing it again (Littlewood et al 2013). This can vary between patients; some may need to perform it every other day whereas others may be able to perform 2xdaily. As they improve, the frequency can increase as they should recover quicker.

Due to the effect of delayed onset of muscle soreness, it is important to ensure that the patients are well educated and plenty of reassurance is provided.

From here, I believe it would be beneficial for studies to look at the combination of eccentrics and stretching compared to just eccentrics. Could the combination provide faster, more beneficial results for flexibility? Also, as touched on previous posts, research investigating the effects of eccentric training on frozen shoulders would be of particular interest.

I will now look into other forms of resistance training to see if any others are as beneficial as eccentrics. One study observing the effects of eccentric loading actually included a concentric phase. The deadlift was used, focusing on a 5 second eccentric phase but 2 second concentric phase, with significant improvements in hamstring flexibility (Nishida et al 2018).

If eccentric loading improves flexibility due to sarcomerogenesis, why not strengthen concentrically as well, ensuring the muscle is taken through its full eccentric range.

References:

American College of Sports Medicine (2017). Resources for the exercise physiologist. 2^nd edition. Philadelphia, Wolters Kluwer Health, page 122.

Andias, R and Silva, A (2019). A systematic review with meta-analysis on functional changes associated with neck pain in adolescents. Musculoskeletal care, [online] 17 (1), pages 23-36. Available at: https://www.ncbi.nlm.nih.gov/pubmed/30629325 [accessed 17th December 2019].

Brukner, P and Khan, K (2018). Clinical sports medicine: Volume 1, Injuries. 5^th edition. Sydney, Mcgraw-Hill education, page 148.

Corbin, C and Noble, L (2013). Flexibility: A major component of physical fitness. Journal of physical education and recreation, [online] 51 (6), pages 23-60. Available at: https://link.springer.com/article/10.1007/s40279-019-01248-w [accessed 2nd January 2020].

Douglas, J et al (2017). Chronic adaptations to eccentric training: a systematic review. Sports medicine, [online] 47, pages 917-941. Available at: https://www.ncbi.nlm.nih.gov/pubmed/27647157 [accessed 3rd January 2020].

Institute of Medicine (2012). Fitness measures and health outcomes in youth. Washington D.C, The national academic press, page 189.

Kenny, S et al (2016). Risk factors for musculoskeletal injury in preprofessional dancers: a systematic review. British journal of sports medicine, [online] 50 (16), pages 997-1003. Available at: https://www.researchgate.net/publication/285543678_Risk_factors_for_musculoskeletal_injury_in_preprofessional_dancers_A_systematic_review [accessed 20th December 2019].

Littlewood, C et al (2013). A review of systematic reviews of the effectiveness of conservative interventions for rotator cuff tendinopathy. Shoulder and elbow, [online] 5 (3), pages 151-167. Available at: https://onlinelibrary.wiley.com/doi/abs/10.1111/sae.12009 [accessed 29th December 2020].

Nishida, S et al (2018). Effect of change in passive stiffness following low-intensity eccentric hamstring exercise on peak torque angle. Journal of physical therapy science, 30 (12), pages 1434-1439.

Nuzzo, J (2019). The Case for Retiring Flexibility as a Major Component of Physical Fitness. Sports medicine, [online] 50, pages 1-18. Available at: https://link.springer.com/article/10.1007/s40279-019-01248-w [accessed 1st January 2020].

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Tencel (2019). When denim is flexible enough for a contortionist. [online]. [accessed 12th January 2020]. Available from: https://carvedinblue.tencel.com/denim-flexible-enough-contortionist/

There are a few relevant studies available that actually compare static stretching with eccentric loading for flexibility, but they all conclude the same thing; both result in significant improvements in flexibility, but there is no significant difference between the two interventions.

The first study to examine these effects was by Nelson and Bandy (2004). They observed a significant improvement in hamstring flexibility following static stretching and eccentric training, compared to a control group over 6 weeks. There was however no significant difference between both groups despite a slightly greater increase following eccentric training. The major flaw to this study was that at the end of the eccentric movement, a 5 second hold was performed. This could be considered a static stretch, which questions whether eccentrics alone would be as beneficial.

Nelson was also involved in a further study in 2006, examining the immediate effects of the same interventions. This time, there was no hold at the end of the eccentric movement. After a total of 30 seconds under load (6 sets of 5 second reps), compared to a 30 second stretch, the eccentric group showed the greatest, most significant increase in flexibility. This response is likely due to the temporary changes in viscoelastic behaviour (O’Sullivan et al 2012). This therefore would support using eccentrics prior to an event if you needed a short-term increase in flexibility.

Both studies by Nelson were performed in high school students, with the latter involving athletes only. Caution must therefore be taken when applying the results to the general population due to the specificity of the population involved.

The most recent study by Askar et al (2015) compared eccentric loading with static stretching and dynamic stretching for hamstring flexibility, whilst also including a control group. Each intervention group contained 22 participants each, performing 1 session a day for 3 days, over a 6 week period.

The results showed that eccentric loading provided the most effective intervention for improving flexibility of the hamstrings, however there was no significant difference between this and static stretching. Both the eccentric and static stretching group were significantly more effective than dynamic stretching and all three provided significant benefits over the control group.

The limitations with the study are that it was performed in regular footballers aged 18-25. This makes it hard to generalise for the whole population, due to the majority of patients being older and more deconditioned. It also follows the usual theme from these studies, in that the participants are not in any pain. They also all only looked at the hamstring muscle. As mentioned in the previous post, this may be due to the perceived importance of hamstring flexibility (American College of Sports Medicine 2018).

An interesting area for more research would be the effects of eccentric loading for frozen shoulders. The current physiotherapy recommendation for frozen shoulders is for stretching and manual therapy, but with a lack of positive results (Uppal et al 2015). Due to the hypo-algesic effect of exercise and the perception of safe movements reducing muscle guarding (Naugle et al 2012), eccentric loading could have a positive effect.

Adam Meakins (2015) has written a blog around the area which can be found here. Unfortunately, there is a lack of research for eccentrics in the upper limb for flexibility, with none looking at frozen shoulder.

From the current available evidence, there appears to be no difference between stretching and eccentric training for improving flexibility. Due to the additional benefits from strength training, would it not make more sense to make the muscles strong as well as long?

As with all research, interventions should be applied to the patients on an individual level though. It is still common for some patients to believe that stretching is a key component to their fitness regime. If they have previously benefitted from stretching, then the belief of the effects can be very powerful (Munnangi and Angus 2019).

Also, there may be patients that struggle with eccentric training due to fatigue and pain (Shokri et al 2018). Eccentric training is associated with post exercise soreness – so should be used in caution and with education with certain patients. If loading eccentrically is too painful for a patient and flares up their symptoms, stretching may be more suitable to achieve greater flexibility.

How important is flexibility though? If the only benefits to static stretching are to improve flexibility, why is this important to us? The next blog will question if flexibility is still as important as previously thought.

References:

American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 10th ed. Philadelphia: Wolters Kluwer; 2018.

Askar, P et al (2015). Effectiveness of eccentric training, dynamic range of motion exercises and static stretching on flexibility of hamstring muscle among football players. International journal of physiotherapy, [online] 2 (6), pages 1012-1018. Available at: https://www.researchgate.net/publication/285746053_EFFECTIVENESS_OF_ECCENTRIC_TRAINING_DYNAMIC_RANGE_OF_MOTION_EXERCISES_AND_STATIC_STRETCHING_ON_FLEXIBILITY_OF_HAMSTRING_MUSCLE_AMONG_FOOTBALL_PLAYERS [accessed 31st December 2020].

Meakins, A (2015). Frozen shoulder? Let it go, let it go…. [blog]. The Sports Physio. Available at: https://www.thesports.physio/2015/11/18/frozen-shoulder-let-it-go-let-it-go/ [accessed 10^th January 2020).

Munnangi, S and Angus, L (2019). Placebo effect [online]. Florida, StatPearls publishing. Available at https://www.ncbi.nlm.nih.gov/books/NBK513296/. [accessed 7th January 2020].

Naugle, K et al (2012). A meta-analytic review of the hypoalgesic effects of exercise. Journal of the American pain society, 13 (12), pages 1139-1150.

Nelson, R (2006). A Comparison of the Immediate Effects of Eccentric Training vs Static Stretch on Hamstring Flexibility in High School and College Athletes. North American journal of sports physiotherapy, [online] 1 (2), pages 56-61. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2953312/ [accessed 4th January 2020].

Nelson, R and Bandy W (2004). Eccentric Training and Static Stretching Improve Hamstring Flexibility of High School Males. Journal of athletic training, [online] 39 (3), pages 254-258. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC522148/ [accessed 4th January 2020].

O’Sullivan, K et O’Sullivan, K et al (2012). The effects of eccentric training on lower limb flexibility: a systematic review. British journal of sports medicine, [online] 46 (12), pages 838-845. Available at: https://www.ncbi.nlm.nih.gov/pubmed/22522590 [accessed 10th December 2019].

Shokri, P et al (2018). Fatigue Induced Effects after Concentric versus Eccentric Exercises on Sense of Force and Senses of Position among Young Normal Adults: A Controlled Single-Blinded Study. Journal of research in medical and dental sciences, 6 (3), pages 258-267.

Uppal, H et al (2015). Frozen shoulder: a systematic review of therapeutic options. World journal of orthopaedics, [online] 6 (2), pages 263-268. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4363808/ [accessed 5th January 2020].

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When we talk about strength training, what comes to mind? Perhaps an image of Arnold Schwarzenegger, with his large muscles and well-defined physique. But did you associate it with flexibility? Strength training has been recognised for so long as a way to improve the size and strength of our muscles. The concept that it can actually improve the length is relatively new.

I mentioned in the last post, how improving the stretch tolerance of a muscle can improve its resting and active length. This does not however change the properties of a muscle. The process for which a muscle increases in length is called sarcomerogenesis, through an addition of sarcomere in the series (Peviani et al 2018). Blazovich et al (2018) suggest that sarcomerogenesis is not a key factor in improving muscle length following stretching. This is due to the lack of increase in fascicle length observed in most human studies, or in sarcomere number in animal stretch models.

Let’s briefly recap the anatomy of a muscle. A muscle fibre consists of myofibrils. These are formed by a series of sarcomeres arranged in a longitudinal alignment. Within a sarcomere are thick filaments of myosin and thin filaments of actin. As a muscle contracts concentrically, the actin and myosin filaments overlap to shorten the sarcomere and create a force (Zollner et al 2012).

(Openstax 2015)

Single muscle fibres are triggered to grow when they detect a mechanical load, through receptors in their cell membranes. In order for all the fibres in the muscle to grow, the muscle should be loaded through its full range. This would suggest why strength training may be perceived to reduce flexibility, as it is common for weightlifters to only work through the strongest part of their muscle which is the mid-range (Beardsley 2018).

During an eccentric contraction, some sarcomeres are stretched beyond myofilament overlap and become disrupted. This disruption grows with repeated contractions, leading to membrane damage (Rassier 2017). This is followed by protein synthesis and sarcomerogenesis in the process of repair. Sarcomerogenesis after eccentric exercise was evidenced by using laser light diffraction to measure sarcomere numbers, in the hind-limb muscles of rats (Brockett et al 2001).

The addition of sarcomeres in series allows muscle fibres to operate at longer lengths, as the muscle is stronger towards the end of its range. This is believed to decrease the potential for further muscle damage as the muscle can withstand greater loads. The result of this is a prolonged shift in the muscle length-tension curve in the direction of longer muscle lengths (O’Sullivan et al 2012).

(Black 2011)

It has been shown that sarcomerogenesis can occur within 10 days of starting eccentric training (Brockett et al 2001). This was performed as 12 sets of 6 repetitions of the Nordic hamstring exercise, however the exercise was only performed on day 1 and day 8. This raises the question for whether more regular training will result in an earlier response.

Mahieu et al (2008) also found that an eccentric training regime provided a significant increase in dorsiflexion range of motion after only 6 weeks. Within this study, the eccentric exercise was a heel drop, performed as 3xsets of 15 reps daily. This increase was accompanied by a decrease in the passive resistive torque, which is further evidence that structural changes occur after eccentric loading.

Both of these studies support the hypothesis that eccentric training can result in the lengthening of muscles. The systematic review by O’Sullivan et al (2012), involving 6 randomised control trials, provided strong evidence that eccentric training provides a significant increase in muscle length, rated as high quality on the pedro scale. The improvement observed was measured as a change in fascicle length as well as range of motion available at the muscle. Fascicle length and range of motion are both closely related to changes in the muscle length-tension curve, supporting the hypothesis that it improves flexibility (O’Sullivan et al 2012).

More recent studies have all arrived at the same conclusion. Abdel-aziem et al (2018) identified improvements in hamstring flexibility and eccentric peak torque following eccentric training. Interestingly, they also observed that the improvement was greater in untrained subjects than in trained. The eccentric intervention was performed for 6xsets of 5 repetitions, 5xper week over a period of 6 weeks in pain-free subjects.

A study of particular interest was the one performed by Muhamad and Muhammad (2018). Although it is another study in pain-free subjects, they observed the effects in overweight and obese females. This is more generalizable than a lot of the studies in athletes due to over 1/3 of the world’s population being overweight or above on the BMI scale (Hruby and Frank 2015). Again, flexibility significantly increased following eccentric training of hamstring muscles compared to a control group of no intervention after 8 weeks.

As you may have noticed, a high proportion of the studies were performed using the hamstring muscle. This may be due to the relative importance of hamstring flexibility to activities of daily living and sports performance (American College of Sports Medicine 2018). They were also only performed in pain-free subjects which limits the generalisability, as the patients we treat are usually in pain.

Eccentric training has also been consistently shown to provide other benefits. It has been observed to reduce the risk of injury, reduce pain and improve strength, power and performance (Douglas et al 2017).

There was recently a period where eccentric loading had gained widespread implementation within the rehabilitation setting. It was widely used in the treatment of tendinopathy, with Alfredsons (1998) protocol being more of the well-known interventions.

More recently, the evidence has suggested that any form of loading appears as beneficial as another, whether it be concentric, eccentric or isometric (Bohm et al 2015). This still suggests that eccentrics have their part to play though, and with the added benefit of improving flexibility they could still provide a useful adjunct in rehab.

If eccentric training can significantly increase muscle length, as well as its other benefits, then do we still need to be performing stretches? Studies comparing the effectiveness of stretching with eccentric training for flexibility would therefore be of particular interest to determine this. One guess what the next post will be about…

References:

Abdel-aziem, A et al (2018). Isokinetic peak torque and flexibility changes of the hamstring muscles after eccentric training: Trained versus untrained subjects. Acta orthopaedica et traumatological turcica, [online] 52 (4), pages 308-314. Available at https://www.ncbi.nlm.nih.gov/pubmed/29803678 [accessed 24th December 2019].

American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 10th ed. Philadelphia: Wolters Kluwer; 2018.

Alfredson, H et al (1998). Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. Journal of Sports Medicine, [online] 26 (3), pages 360-366. Available at: https://www.ncbi.nlm.nih.gov/pubmed/9617396 [accessed 12th January 2020].

Beardsley, C (2018). What is muscle growth and how does it happen? [blog] medium. Available at: https://medium.com/@SandCResearch/what-is-muscle-growth-and-how-does-it-happen-b7f7cd68ee34. Last accessed 26^th December 2019.

Blazevich, A (2018). Adaptations in the passive mechanical properties of skeletal muscle to altered patterns of use. Journal of applied Physiology, [online] 126 (5), pages 1483-1491. Available at: https://www.ncbi.nlm.nih.gov/pubmed/30412028 [accessed 2nd January 2020].

Bohm, S et al (2015). Human tendon adaptation in response to mechanical loading: a systematic review and meta-analysis of exercise intervention studies on healthy adults. Sports medicine – open, 1 (7).

Brockett, C et al (2001). Human hamstring muscles adapt to eccentric exercise by changing optimum length. Medicine and science in sports and exercise, 33 (5), pages 783-790.

Douglas, J et al (2017). Chronic adaptations to eccentric training: a systematic review. Sports medicine, [online] 47, pages 917-941. Available at: https://www.ncbi.nlm.nih.gov/pubmed/27647157 [accessed 1st January 2020].

Ferreira, D et al (2007). Analysis of the influence of static stretching and eccentric training on flexibility of hamstring muscles. International Symposium on Biomechanics in Sports, 25.

Hruby, A and Frank B (2015). The epidemiology of obesity: A big picture. Pharmacoeconomics, [online] 33 (7), pages 673-689. Available at https://www.ncbi.nlm.nih.gov/pubmed/25471927 [accessed 1st January 2020].

Lynn, R et al (1998). Differences in rat skeletal muscles after incline and decline running. Journal of applied Physiology, 85 (1), pages 98–104.

Mahieu, A et al (2008). Effect of eccentric training on the plantar flexor muscle-tendon tissue properties. Medicine and science in sports and exercise, 40 (1), pages 117-123.

Muhamad and Muhammad (2018). Effects of 8 weeks of eccentric training on hamstring flexibility and muscular performance among healthy overweight and obese women. International journal of public health and clinical sciences, [online] 5 (3), pages 192-203. Available at: http://publichealthmy.org/ejournal/ojs2/index.php/ijphcs/article/view/634 [accessed 3rd January 2020].

O’Sullivan, K et al (2012). The effects of eccentric training on lower limb flexibility: a systematic review. British journal of sports medicine, [online] 46 (12), pages 838-845. Available at: https://www.ncbi.nlm.nih.gov/pubmed/22522590 [accessed 10th December 2019].

Peviani, S et al (2018). Regulation of extracellular matrix elements and sarcomerogenesis in response to different periods of passive stretching in the soleus muscle of rats. Scientific reports, 8 (9010).

Rassier, D (2017). Sarcomere mechanics in striated muscle: from molecules to sarcomeres to cells. American journal of physiology, 313 (2), pages 134-145.

Zollner, A et al (2012). Stretching skeletal muscle: chronic muscle lengthening through sarcomerogenesis. Plos one, [online] 7 (10). Available at: https://www.ncbi.nlm.nih.gov/pubmed/23049683 [accessed 1st January 2020].

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Stretching is well known about and used worldwide. An international survey revealed 53% of physically active adults normally stretch and 80% of personal trainers in the United States prescribe it (Nuzzo 2019). We may stretch because we have been advised by a medical professional, or because it just seems like the right thing to do. But why do we actually do it?

Stretching can be seen as an innate behaviour, as observed by cats after waking from a long sleep. It is also instinctive in humans to yawn and stretch after waking, even babies do it. This is known as pandiculation (Warren 2019). A lot of animals do this (30-40 times per day) to prepare their body for activity (Essential Somatics 2015).

Pandiculation is our innate response to the sensations of lack of movement and to tension building up in our muscles. The science behind it is that it reverses the muscular-atonia of the REM-sleep (Walusinski 2006). It is also supposed to improve blood flow and reduce stress, by activating the parasympathetic nervous system. The yawn increases oxygen intake into the lungs, while the muscle lengthening increases the heart rate through activating muscles and encouraging blood flow to extremities (Farinatti et al 2011).

Pandiculation is however different to static stretching. When you pandiculate, you are contracting your muscles in order to lengthen them and reach the end of its range (Essential Somatics 2015). The “cat stretch” often performed in pilates is actually based on a cat eccentrically lengthening its back muscles.

Passive stretching involves holding a muscle in its lengthened position using external force – a partner, object or another limb. Despite the name, it is actually not entirely passive due to the small force applied to the muscle (De Deyne 2001).

So have we got it all wrong? If animals eccentrically contract their muscles to regain their length, why are we trying to passively stretch them?

Stretching was first recognised in an osteological study in the 18^th century, however it can be dated back to the Hippocratic era (460 BCE) when the roman empire would use it to keep their gladiators in shape (Tipton 2014).

Hippocrates was the first recorded physician to prescribe a written exercise programme (Tipton 2014). He believed that it was possible to have a stronger and more rested body after exercise, through walking (hence why we now cool-down after exercise), baths, massage and stretching (Redman 1846). A lot of his advice is still used today, however these were based on theory which in the modern day, would be at the bottom of the hierarchy of evidence. 

Stretching generally focuses on increasing the length of a musculotendinous unit, in essence increasing the distance between two joints and holding for an extended period (Brukner and Khan 2017). The prior belief was that the prolonged tension applied by a stretch on a muscle overcomes the force of connective tissue in order to increase the length (Roberts 1995). Imagine stretching out some plasticine and seeing how it holds its new elongated shape.

Other studies contradicted this. Crawford (1973) found that when immobilising the muscle of young rabbit in the extended position, there was actually a reduction in sarcomere addition. The muscle belly of the immobilised limb was actually shorter after the trial and it was in fact the lengthening of tendon that resulted in the increased range. This indicated the importance of movement in stimulating normal growth. The increase in tendon length has been suggested to be due to the isometric contractions of the rabbit trying to move when immobilised.

Williams and Goldspink (1978) then found that an increase in skeletal muscle length has been shown to result from the serial addition of sarcomeres. This was measured in both the postnatal development of mice and adult mice. This increase in sarcomeres is referred to as sarcomerogenesis and will be discussed in my next blog.

The limitations to these studies are that they both used animals and also involved a very long period of immobilization. As far as I know, no physio is recommending to patients to splint their muscles for a few months in order to improve flexibility.

More recent research shows that the reason the muscles extensibility improves through stretching is that the stretch tolerance of the muscles improves. This is by habituation of the protective stretch reflex to the stretching sensation (Weppler and Magnusson 2010). This would suggest that stretching does have a positive effect on flexibility and has been consistently proven to do so (Apostolopoulos et al 2015).

The current recommendation for stretching is for a slow, sustained stretch of at least 10-15 seconds. The intensity, duration and frequency should increase as flexibility improves and it should also be pain-free (Bruckner and Khan 2017). Many studies have looked at the frequency of stretching required in order to significantly improve range of motion. The most beneficial effects appear to be when performing them at least 3xper week (Apostolopoulos et al 2015).

Stretching has also been thought to be beneficial for injury prevention and improving performance (Hartig and Henderson 1999). Again though, more recent evidence suggests that this is not always the case. Research consistently found a reduction in power immediately after static stretching (Behm and Chaouachi 2011). This prompted the shift for more dynamic stretching to be performed prior to exercise.

Lauersen et al (2014) performed a systematic review looking at the effectiveness of exercise interventions at preventing sports injuries. Strength training had a significant effect in reducing injuries however stretching had no beneficial effect. It is however important to point out that the systematic review only included two studies on army recruits and one internet-based study on the general population for stretching. Therefore, we should tread carefully when applying this information for all sports, such as dance and contortion where flexibility may be deemed more important.

The current recommendation based on the evidence is therefore that stretches can be used to improve flexibility, but are there more effective ways to achieve this? The next post will look at alternative methods to decipher what is most effective.

References

Apostolopoulos, N et al (2015). The relevance of stretch intensity and position – a systematic review. Frontiers in Psychology, [online] 6, page 1128. Available at https://www.frontiersin.org/articles/10.3389/fpsyg.2015.01128/full#h1. [Accessed 24th November 2019].

Behm, D and Chaouachi, A (2011). A review of the acute effects of static and dynamic stretching on performance. Applied Physiology, [online] 111 (11), pages 2633-2651. Available at https://link.springer.com/article/10.1007%2Fs00421-011-1879-2#citeas [accessed 24^th November 2019].

Crawford, G (1973). The growth of striated muscle immobilized in extension. Journal of anatomy, 114 (2), pages 165-183.

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If stretching is the answer, then what is the question? I used to believe that treating musculoskeletal conditions was simple; strengthen what is weak and stretch what is tight. The biopsychosocial model has however proven it is not so straightforward to manage pain. But what does the evidence suggest when it comes to flexibility? Is stretching still the gold standard?

I have come to realise through my time as a Physio that “the more you know, the less you understand” couldn’t be truer. By trying to find an answer to a particular topic, time and again I have ended up with more questions than when I started. Due to the vast evidence base and widely split opinions on treatment, finding the ‘answer’ can be difficult. My aim throughout my blogs is to summarise the best up-to-date evidence to determine if static stretching is still relevant in our practice.

When I was a student, social media wasn’t used for healthcare as heavily as it is now. This meant that there was not the guidance from other clinicians highlighting what the current evidence suggests. Keeping up with the most recent and high-quality evidence was therefore a lot harder than it is now. As a result, my initial practice was shaped from previous clinical educators on placement – if their practice was outdated, then so was mine.

Upon qualifying, I therefore had my first experience of ‘Imposter syndrome’ when my new colleagues questioned my ancient methods. Since then, I have strived to keep up to date to avoid becoming a ‘dinosaur physiotherapist’.

Despite only qualifying 4 years ago, stretches at that time still appeared to be a popular treatment method. They were used to help manage pain, improve flexibility and even prepare the body for activity (Hartig and Henderson 1999). It wasn’t until recently where they have come under more scrutiny. They are still regularly used by clinicians, however there appears to be more and more studies questioning its effects. Are they beneficial in reducing pain? Do they help to prevent injury? How effective are they at improving flexibility?

As a newly qualified physio, a large focus of my assessment was observing for abnormalities in posture, looking for what might be tight in order to locate what I believed to be causing the patients pain. Recent evidence however suggests that posture isn’t as important as previously thought in relation to pain (Slater et al 2019).

I first started questioning the effectiveness of stretching in my own practice when upon re-assessment, patients would demonstrate an improvement in muscle length but no change in symptoms. I also had patients returning to see me with an increase in their symptoms following advice to stretch. Based on this, what exactly was the role of stretching in my treatment plan and what are they trying to achieve?

Since then, I have had a particular interest in stretching as a form of treatment. Our time as Physiotherapists is precious, especially working within the time constraints of the NHS. Our patients also understandably want to be better as quickly as possible. Are stretches worth investing in or are they only lengthening the time to recovery?

Keep up to date with my blog, where I will look to collate the evidence to determine whether stretches should be a thing of the past, or if they still have a role to play in our practice.

References:

Hartig, D and Henderson, J.  Increasing hamstrings flexibility decreases lower extremity overuse injuries in Military Basic Trainees. American Journal of Sports Medicine, [online] 27 (2), pages 173–176. Available at https://journals.sagepub.com/doi/abs/10.1177/03635465990270021001. [accessed 20th November 2019].

Slater, D et al 2019. “Sit up straight”: Time to Re-evaluate. Journal of orthopaedic and sports physical therapy, 49 (8), pp562-564.

Images:

McGuire, R (2019). Stretching Sports Woman. [online]. [Accessed 10th November 2019]. Available from: https://www.needpix.com/photo/260409/stretching-sports-woman-athlete-fitness-sport-healthy-exercise-workout.

Wintecare, S (2018). T-rex physio at the European championships. [online]. [accessed 12th January 2020]. Available from: https://www.youtube.com/watch?v=1-Av4Dq6gdM