This question is a productive one. It gives an opportunity to examine the logic of the classical rehabilitation approach reasoning regarding passive stretching in great detail. I will try to present, step by step, the thought process which brought to the conclusions which are integrated in the classical rehabilitation paradigm. Therapeutic procedures used in practice are built based on those conclusions and assumptions.
Healthy individuals
I would start with pointing out an obvious observation: with the application of passive stretching of the muscles in healthy individuals and athletes, it is possible to achieve an increase of the motion range in the joints and elasticity of the soft tissues. Reasonable results of this therapeutic procedure are shown in traumatology, too. After knee surgery for example, the procedure is used to recover normal range of motion of the joint. In most of the cases it is reasonably successful.
There is scientific literature, articles which explain passive stretching effects in healthy individuals, athletes and people who rehabilitate after injuries and surgeries. Even if we do not dig into science, but try to rely on our common sense and life experience, we know this idea is reliable.
What do I mean by reliable? If you would make a program of body stretching and conduct it for a prolonged period, you would probably achieve a significant increase in muscle and soft tissue elasticity, and body mobility. We know this even from our own experience. Obviously, that works. Surely, in this case we talk about the absence of brain damage and presence of normal muscle tone.
Individuals with cerebral palsy and other neurological conditions and diseases
For easier comprehension of the points I would like to make, I tend to differentiate between the two components of these conditions and diseases. If we take passive stretching as a therapeutic procedure of choice, on the one hand, we can observe the neurological component in the form of the brain damage, and the body structure component in the form of altered muscles and connective tissue structures (myofascial structures).
- Neurological component[1]
In a person with cerebral palsy (CP) and other neurological conditions and diseases, increased muscle tone can be present in certain muscles or muscle groups in the form of spasticity or rigidity. Spasticity [2] is a condition in which certain muscles or muscle groups are continuously contracted. Spasticity is caused by a brain lesion that occurs in the part called the Pyramidal tract. Rigidity is also a condition in which certain muscles or muscle groups are continuously contracted. It is caused by a brain lesion that occurs in the part called Basal ganglia or Extra-Pyramidal tract. Spasticity and rigidity interfere with normal movement control, range of motion of the joints and generally negatively influence the motor functions and skills of the person. I would mention that what I call the neurological component is clear to most of the parents because it is more or less explained by health care professionals.
- Body structure component[3]
New scientific findings show that structural alterations in people with cerebral palsy are present in:
– muscle tissue (muscle fibres)
– collagen fibres (fibrous part of connective tissue)
– extracellular matrix (ECM- the liquid part of connective tissue).
It is suggested (Booth, C., Cortina-Borja, M., & Theologis, T. 2001) that “muscle function often becomes progressively more compromised in children with spastic cerebral palsy, leading to reduced mobility… Collagen I accumulated in spastic muscle’s endomysium which appeared to be thickened, and fibrotic regions with sparse muscle fibres were evident in more severe cases. This suggests that collagen may be involved in increases in muscle stiffness observed in spasticity”.
Further, related to ECM alterations (Smith, L.R., Lee, K.S., Ward, S.R., Chambers, H.G. and Lieber, R.L. 2011) it is explained that “Muscle spasticity, due to an upper motor neuron lesion, often leads to muscle contractures that limit the range of motion and cause increased muscle stiffness… Here we show that muscle tissue is stiffer in contracture compared to age‐matched children, implicating the extracellular matrix (ECM)… Increased ECM stiffness is even more functionally significant given our finding of long in vivo sarcomeres which leads to much larger in vivo forces in muscle contracture. These results may lead to novel therapeutics for treating spastic muscle contracture”.
The idea behind citing these researches is to bring to parents’ attention, the importance of bodily structure alterations which need to be taken into account regarding the effects of passive stretching on spastic or rigid muscles. Most parents are not aware of the body structure component because the classical rehabilitation system takes into consideration only the neurological component. Why? — you may ask. I worked in that system and my observation is that the analytical tools that they use to make conclusions and decisions regarding therapeutic procedures in the rehabilitation process are simple and one-directional. What does that mean in practice?
Simple reasoning: in cases of spastic and rigid cerebral palsy, muscles are shortened, the normal range of motion is reduced. If we want to achieve results, we will do the opposite: we will stretch shortened muscles and try to improve the range of motion. If we do not do that, muscles will get even shorter, which will bring to the development of contractures and later, deformities. This will happen because the brain is damaged and spastic muscles are permanently being bombarded with electrical signals which make them constantly contracted. That is all.
As cerebral palsy and other neurological conditions and diseases which involve spasticity and rigidity are primarily the results of brain damage, this explanation is not wrong. But it is incomplete. Scientific findings confirm, as I mentioned, that either primary or secondary changes in the connective tissues and muscles negatively influence spasticity and rigidity in these populations.
In order to be able to understand if passive stretching brings positive results, we need to analyse it in the context of both components: neurological and structural. We also have to understand how the neurological component influences the structural one and vice versa.
We now understand that there are significant differences between healthy and altered muscles and connective tissues. They are different from the neurological and structural standpoint. Healthy and altered muscles and connective tissues show different structural and mechanical properties.
The simple question is: how can we apply the same therapeutic procedure (passive stretching) on the body structures which have such different qualities and expect them to react in the same way?
How can we expect to achieve the same results? In my opinion, it is logical: if you apply the same procedure on the body structures which show different properties, you will get a different response and different final result. This is the main reason why passive stretching if applied to a healthy bodily structure, will show benefit, and if applied on altered bodily structure, it will show very little or no benefits or even in the long run, it will result in deterioration of the treated body structure.
(Pin, T., Dyke, P., & Chan, M. 2006). Passive stretching is widely used for individuals with spasticity in a belief that the tightness or contracture of the soft tissues can be corrected and lengthened. The evidence for the efficiency of passive stretching on individuals with spasticity is limited. The aim of this review was to evaluate the evidence on the effectiveness of passive stretching in children with spastic cerebral palsy. Seven studies were selected according to the selection criteria and scored against the Physiotherapy Evidence Database scale. Effect size and 95% confidence intervals were calculated for comparison. There was limited evidence that manual stretching can increase the range of movements, reduce spasticity, or improve walking efficiency in children with spasticity.
In the next article, I will discuss in more detail what happens to the connective and muscle tissue as a consequence of brain injury, how that affects further movement control and body structure development and why parents should be very careful about passive stretching application.
[1] Dystonia and muscle hypo-tone are neurological components of cerebral palsy and some neurological disorders but they will not be elaborated in this article as passive stretching is a therapeutic procedure which obviously will not be used to address those problems, thus they do not have any significance regarding this topic.
[2] In this text, I just want to point out some basics, therefore the difference between spasticity and rigidity will be explained in one of the next articles.
[3] Joint stiffness, joint hypermobility, joint instability; shortened tendons and ligaments and contractures all fall under the umbrella of altered connective tissue term.
