Originally Posted by sentii
Hi guys, I was just curious what the rationale is for the cyclic stretching exactly. That one paper mentions that cyclic stretching was used and that every cycle got closer to an eventual maximum strain, but it didn’t actually say that doing things cyclically was more effective than doing just a steady stretch, unless I’m mistaken. Just curious if you particularly read somewhere that cyclic loading was superior to uninterrupted stretching. Thanks ahead for any further elaboration on the basis of the cyclical approach you might be able to provide. This is all very exciting.
Viscoelastic nature of the tissues we are trying to elongate.
This has been debated in my log starting at the page 15 I suppose.
Looking at the papers we should always look what they were doing and can the results be emulated in to situation we are going on. If the studies use loads that operate in the fully elastic range of the stress strain curve then there is not much difference in the outcome. Or if the aim was to investigate the difference in mobility of the joint stretching the ligaments cold there might be not so much difference in the outcome.
But we are not operating at the range the tissues behaves fully elastic, which would need very long lasting hanging with tens of pounds used as a load.
We are operating at the transitional area between the toe region and the proportional range(elastic range).
It is the zone where tissue drastically stiffens and exponentially resists any additional elongation occurring.
Look what the papers say about non-linear elasticity of the visco-elastic biological tissues and you found the reasoning. Pushing through the stiffening caused by the visco-elastic behavior the cyclical stretching is the way which results the best outcome in given time.
The graph attached shows pretty much the reasoning. If the visco-elastic tissue is loaded it stiffens and it takes time for to relax and lose the resisting force. Releasing the load there is hysteresis which causes the tissue recover slowly to the resting length, Also the more load or with a higher velocity the load is applied the greater is the resisting response.
The graph shows how repeated loading eases the resisting force and how many repetitions is needed to stabilize the behavior. The slow introducing of the force is the superior way to handle visco-elasticity. And if we are going to repeat the loading before the full recovery time we are starting the next loading phase at incrementally longer state each time.
All manual stretching is cyclical or dynamic by it´s nature of course. The timing of the cooldown stretch comes from the combination of the ultrasound studies indicating that there is a 10 minutes window for the stretching after the US application is removed, and secondly from several sources indicating what the graph shows, minimum of ten repetitions is needed to tackle the visco-elasticity induced resistance.
In addition the collagenous tissue is quite different animal if there is therapeutic heat applied or not.
hysteresis.PNG
START 18/13.15 cm Jul 24th 18 (7.09/5.18") NOW 22.5/15.2 cm Fer 12th 20 (8.86/5.98") GOAL 8.5"/ 6"
When connective tissue is stretched within therapeutic temperatures ranging 102 to 110 F (38.9- 43.3 C), the amount of structural weakening produced by a given amount of tissue elongation varies inversely with the temperature. This is apparently related to the progressive increase in the viscous flow properties of the collagenous tissue when it is heated. (Warren et al (1971,1976)