I started my martial arts journey in the eighties, so it's safe to say that I have seen and tried practically every stretching method that has ever existed. Dynamic, static, isometric, loaded, assisted, facilitated - you name it, I've done it. I got good results with some, not so good with others.
My preference has always been for isometric stretching (originally called PNF, or proprioceptive neuromuscular facilitation). Isometric stretching involves contracting lengthened muscles to produce substantial increases in range of motion. Isometrics have always worked best for me, but that's probably because I never really had the patience to sit in passive holds for any length of time, rather than static passive stretching being a less effective method. However, static passive stretching effectively reduces musculotendinous stiffness (Nakamura et al., 2014), so it's precisely what I need to do, given my naturally high levels of tissue stiffness.
But there is one method of stretching I have always done my best to avoid: ballistic stretching. It is, strictly speaking, a type of dynamic active stretching (although it may be dynamic passive too, under certain conditions). In a ballistic stretch, a person attempts to create more range of motion by rapidly bouncing or bobbing at their limit of tissue extensibility.
Ballistic stretching was everywhere in the eighties, although it tended to be more prevalent in Chinese martial arts systems like kung fu rather than the karate and taekwondo in which I trained. I always believed ballistic stretching was a bad idea. I never saw anyone develop fantastic flexibility with it, and it just looked like an invitation for injury.
Human tissues are viscoelastic, which means they possess both viscous and elastic properties. Viscosity is a characteristic of fluid materials related to their resistance to flow or how easily the fluid moves through a particular area. (Human tissues possess a high fluid content.) Elasticity is the ability of a material to return to its original shape or length after a deforming force is removed. Viscoelasticity is an essential concept in biomechanics because it tells us how the forces that arise in tissues during motions like stretching depend on time and deformation.
Viscoelastic materials resist deformation when subjected to forces at higher rates. So the faster you try to stretch, the more your tissues will fight against you. As a result, you may be encouraged to try and push harder and faster, ultimately subjecting your tissues to stronger (and potentially damaging) forces (Taylor et al., 1990).
Ballistic stretching may also cause the nervous system to fight harder against the rapid tissue lengthening. Dynamic stretching typically excites the sensory structures that detect both the size and speed of muscle elongation, which partly explains why the literature often reports positive effects on muscle performance (Opplert & Babault, 2017). On the other hand, ballistic stretching can produce adverse effects on performance (Nelson & Kokkonen, 2001; Unick et al., 2005). The rapid, bouncing motion utilised in ballistic stretches causes intense, reflexive contractions of the stretched muscles (Matthews, 1980). These factors help to clarify why ballistic stretching routinely produces less range of motion compared to dynamic active, static active (isometric), and static passive stretching (Covert et al., 2010; Bacurau et al., 2009).
Compared to other, more effective and safer methods of flexibility training, ballistic stretching is an inefficient approach to increasing range of motion. It also carries an inherently higher risk of tissue damage, which may announce itself as the soreness that trainees commonly report after a ballistic stretching session. However, understand that I'm not claiming ballistic stretching is entirely useless. On the contrary, it may confer some benefit during activities that incorporate rapid stretch-shortening cycles, but that is a subject that I'll discuss in a future blog post.
Nakamura, M., Ikezoe, T., Kobayashi, T., Umegaki, H., Takeno, Y., Nishishita, S., and Ichihashi, N. (2014) Acute Effects of Static Stretching on Muscle Hardness of the Medial Gastrocnemius Muscle Belly in Humans: An Ultrasonic Shear-Wave Elastography Study. Ultrasound in Medicine and Biology vol. 40, no. 9, pp. 1991-1997.
Taylor, D. C., Dalton, J. D., Jr., Seaber, A. V., & Garrett, W. E., Jr. (1990) Viscoelastic Properties of Muscle-Tendon Units. The Biomechanical Effects of Stretching. American Journal of Sports Medicine vol. 18, no. 3, pp. 300-309.
Opplert, J. & Babault, N. (2017) Acute Effects of Dynamic Stretching on Muscle Flexibility and Performance: An Analysis of the Current Literature. Sports Medicine vol. 48, no. 2, pp. 299-325.
Nelson, A. & Kokkonen, J. (2001) Acute Ballistic Muscle Stretching Inhibits Maximal Strength Performance. Research Quarterly for Exercise and Sport vol. 72, pp. 415-419.
Unick, J., Kieffer, H. S., Cheesman, W., & Feeney, A. (2005) The Acute Effects of Static and Ballistic Stretching on Vertical Jump Performance in Trained Women. Journal of Strength and Conditioning Research vol. 19, pp. 206-212.
Matthews, P. B. C. (1980) Developing Views on the Muscle Spindle. In: Spinal and Supraspinal Mechanisms of Voluntary Motor Control and Locomotion. J. E. Desmedt, ed. Basel: Karger, pp. 12-27.
Covert, C. A., Alexander, M. P., Petronis, J. J., & Davis, D. S. (2010) Comparison of Ballistic and Static Stretching on Hamstring Muscle Length Using an Equal Stretching Dose. Journal of Strength and Conditioning Research vol. 24, pp. 3008-3014.
Bacurau, R. F., Monteiro, G. A., Ugrinowitsch, C., Tricoli, V., Cabral, L. F., & Aoki, M. S. (2009) Acute Effect of a Ballistic and a Static Stretching Exercise Bout on Flexibility and Maximal Strength. Journal of Strength and Conditioning Research vol. 23, pp. 304-308.