The theme song from Frozen may as well be the mantra for many yoga classes –  where letting go, surrendering, and opening your (fill in the blank) are seductively crooned by the teacher at the front of the room, perhaps only a little less emphatically than Elsa’s performance. Such songs of the Sirens are layered in meaning, dispensing a wide range of advice both psychological and physical. To be told to “let it go” may be considered a form of personal coaching; an insight into how to handle the inevitable upsets in life. The same message, however, may also suggest that enhanced flexibility, greater range of motion, and those distant and aspiring asana are the tangible reward for surrendering.

It’s beautiful, it’s poetic, it’s yoga.

And I’m not arguing against it. But I am offering another perspective, another approach to flexibility.  One that has emerged through a healthy interest  manic obsession with the scientific literature. One that is not intended to replace the old paradigm, but rather to add to it.

I introduce to you the theory of the neural reflex mechanism. This theory establishes relaxation of the contractile components of the target muscle as the mechanism by which greater lengthening occurs [1,2].  Essentially, as your muscle resists a stretch, electromyographic (EMG) activity increases and a reflexive shortening contraction would prevent further lengthening.

In order to bypass this reflexive shortening contraction, one should attempt  to decrease  EMG activity (marking muscle relaxation) in order to achieve new and greater ranges of motion (ROMs).  Just let it go (“it” being the target muscle).  Relax into the stretch, deepen the stretch.. you get the idea.

Research shows, however, EMG activity and force production may actually increase at these new increased ROMs [3]. Stretching methods which result in the greatest improvements in ROM are actually correlated with greater EMG activity; muscle relaxation is not a requirement for increased range of motion [4,5].

In addition to relaxing into the stretch to improve flexibility, techniques that intend to alter or reduce the reflex which resist the stretch are often cued.  Such techniques you may have heard of are reciprocal inhibition (RI) and autogenic inhibition (AI).  The effect of these reflex activities on long term flexbility are questioned by many scientists [6-8], a topic for future blogs.

In the meantime, I challenge you to a forward bend (seated or standing) where you isometrically contract your hamstrings (target muscle) instead of contracting the quadriceps. Did you lose ROM?  Probably not.  Plus the isometric contraction is loading your hamstring tendons to adaptively increase their capacity to withstand a tensile load – bonus for those of who have suffered a hamstring tendon injury.


Personally, I reserve my letting go for restorative yoga. I mean fully supported, 100% supported restorative yoga, where you aren’t feeling that stretching sensation we are all addicted to. That’s really the best way surrender and quiet that EMG activity. And it has little to do with flexibility, but a lot to do with collagen organization and mechanoreceptor stimulation – topics for future blogs.


[1] Guissard, N., & Duchateau, J. (2004). Effect of static stretch training on neural and mechanical properties of the human plantar-flexor muscles. Muscle & Nerve, 29, 248–55. doi:10.1002/mus.10549

[2] Guissard, N., & Duchateau, J. (2006). Neural aspects of muscle stretching. Exercise and Sport Sciences Reviews, 34(4), 154–158.

[3] Magnusson, S. P., Simonsen, E. B., Aagaard, P., Gleim, G. W., McHugh, M. P., & Kjaer, M. (1995). Viscoelastic response to repeated static stretching in the human hamstring muscle. Scandinavian Journal of Medicine & Science in Sports, 5(6), 342–347.

[4] Moore, M. A., & Hutton, R. S. (1980). Electromyographic investigation of muscle stretching techniques. Medicine & Science in Sports & Exercise, 12(5), 322–329. doi:10.1249/00005768-198012050-00004

[5] Osternig, L. R., Robertson, R. N., Troxel, R. K., & Hansen, P. (1990). Differential responses to proprioceptive neuromuscular facilitation (PNF) stretch techniques. Medicine & Science in Sports & Exercise, 22(1), 106–111. doi:10.1249/00005768-199002000-00017

[6] Hayes, B. T., Harter, R. A., Widrick, J. J., Williams, D. P., Hoffman, M. A., & Hicks-Little, C. A. (2012). Lack of neuromuscular origins of adaptation after a long-term stretching program. Journal of Sport Rehabilitation, 21(2), 99–106.

[7] Hindle, K. B., Whitcomb, T. J., Briggs, W. O., & Hong, J. (2012). Proprioceptive Neuromuscular Facilitation (PNF): Its Mechanisms and Effects on Range of Motion and Muscular Function. Journal of Human Kinetics, 31, 105–113. doi:10.2478/v10078-012-0011-y

[8] Sharman, M. J., Cresswell, A. G., & Riek, S. (2006). Proprioceptive Neuromuscular Facilitation Stretching Mechanisms and Clinical Implications. Sports Medicine, 36(11), 929–939.