At the start of my apprenticeship I’ve been told that the most effective way of stretching is dynamic stretching.
Is it this kind of simple?
- Nerve System
- Capsule & Ligaments (Wright 1962)
Why should we aim the optimal muscle length?
An optimal muscle length would allow an
- optimal range extensibility and joint motion
- optimal tendon length,
- overlap of contractile tissue filaments,
- overall muscle thickness
so that the muscle can generate the amount of passive and active tension required during function. But the methods in the current literature seem to vary and depend on intervention duration, volume, intensity (Freitas et al. 2016) and muscle (Ingraham 2008) itself. Most studies are limited in time whereas we actually don’t know when the muscle structure changes. Biomechanical effects of long-term and chronic stretching programs have not been evaluated yet. One can work with different models like
- viscoelastic deformation – more likely to be transient,
Increase in sarcomeres – no overall change in muscle length because increase in sarcomere were offset by a concurrent decrease in sarcomere length,
Neuromuscular relaxation – induce ability to relax while stretching
All in all transient effect on muscle in nature (Wepper et al.).
The most practical model for stretching is „The sensory model“. It describes the first sensation of pain within the stretch tolerance. In general muscle extensibility is one dimensional testing of the length and may no accurately represent actual length of the muscle. More precise measurement is the torque/angle curve for a more individual perspective and with more information about the biomechanical properties of the muscle. This leads to the sensory theory:
„sensation is usually a limiting factor rather than passive muscle stiffness (Weppleret al. 2016)“
Static stretching (–3.7%), Dynamic stretching (+1.3%) and PNF (–4.4%) (with muscle activation close to a stretch) induced performance changes when testing soon after the stretching (Behm 2016).
Repeat it: Practice doesn’t make perfect but perfect practice makes perfect
– think functional!
– use it or loose it!
Target muscle groups known to be at risk for a particular sport/activity (McHugh 2009). For example hamstrings in football.
– think specific!
Hence, stretching in some form appears to be of greater benefit than cost (in terms of performance, ROM and injury) but the type of stretching chosen and the make-up of the stretch routine, will depend on the context within which it is used.
Baxter C, McNaughtonLR, Sparks A, Norton L, Bentley D. 2017. Impact ofstretchingon theperformanceandinjuryriskoflong-distancerunners. Research in Sports Medicine, 25:1, 78-90.