Flexibility

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].

Images:

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