The Loose Art of Stretching....

Why do we stretch? Well, there can only be one answer, because we feel stiff or tight. So what is it about our tissues that make them feel stiff and what is the definition of stiffness? Stiffness is the resistance to deformation in response to an applied force. To help us make sense of this strange sentence we need to understand the human body a little bit better. The human body is made up of connective tissue which is the material that gives it support and shape such as muscle, bone, ligament, skin and cartilage. The main constituents of connective tissue are collagen and elastin.

Collagen is a strongly bonded molecule in the shape of a triple helix – think of a flump that provides structure and strength. Elastin provides elasticity which allows the tissue to recover its original length.

What bathes these tissues is water as we are 60% water (the technical term is the ground substance), this lends viscoelastic properties to the tissues. Water has a low viscosity because it has a low resistance to flow. This relates to how strongly the molecules in the material are bonded together as well as how closely packed they are. It also means it gets everywhere when disaster strikes.

So I mentioned the term deformation which is defined as stress/strain. This is the act of stretching itself where stress = force applied to the tissues and strain = deformation resulting from the stress. Have a look at my flump below, my fingers are providing the stress and the increase in length is the strain.

What other factors affect the stiffness of tissues?
The one that we are most familiar will be temperature. When connective tissue is cold there is an increase in the tissue stiffness, most likely due to an increase in the viscosity (stiffness) of the ground substance (water and proteins). Think of the difference between warm freshly baked bread that is soft and malleable and frozen bread that is hard and brittle (meaning it will break without bending).

Our tissues are exactly the same – due to the energy transfer from an increase in temperature or repetitive movement, there is a change in the stiffness. This will help explain why you do a warm-up before sport or rub stiff and sore muscles.

Other issues that will impact on the tissues are…

• Injury – results in scar tissue which results in stiffness due to disorganisation of the collagen (think flump)
  
  
• Inactivity/immobilisation – results in decreased volume and production of collagen fibres which results in decreased flexibility. Associated disorganisation of the collagen fibres will cause stiffness as it does in injury.
  
  
• Age – Tissue in older people are stiffer due to decreased volume and production of collagen fibres.

So we now have a better understanding of stiffness and the factors that affect this in the human body but what is the science of stretching?

If you stand up and try and touch your toes like the man above – you will feel a tight uncomfortable feeling the back of your thighs, which indicates that the hamstring muscles have reached their maximum length. If you hold your hands in the same position and count slowly to 20 there will be a marked decrease in the uncomfortable tight feeling. This decrease in tension within the muscle is called stress relaxation.

If you wait a few minutes and repeat the process – this time when you feel the tissue decrease in tension stretch down a little further. This will result in you being able to reach down further because there will be an increase in the length of the tissues. This is called creep.

In both stress relaxation and creep the collagen fibres were allowed to slide past each other a certain amount. Without further stress, this results in a decrease in tension within the muscle i.e stress relaxation. If the stress is maintained there is an increase in length i.e creep.

The changes in tissue length due to creep are short-lived because the collagen begins to revert back to its original length (due to the reabsorption of energy and the presence of elastin). Elongation will last anywhere from 30-90 minutes depending on what you are doing – if you are moving around it will last longer.

So it turns out that most of the benefits of stretching are short-lived associated with the transfer of energy/alteration in temperature or an increase in stretch tolerance. To make a lasting change we need to alter the habitual daily stress the tissue goes through or the length that the muscle are held in.

So this means that if we feel stiff and tight it is a signal to move to unload the tissue and not something to be worried about……

So what are the principles of stretching that we need to follow?

• Stretch slowly to the point of resistance
• Hold for 30seconds if under 65 and 1 minute if over 65
• Repeat stretch x 2
  
  

For sports:

• Do not slowly stretch as part of your warm-up if sport relies on speed and power
• Dynamic stretches should be done as part of a dynamic warm-up
• You may tighten up due to the nature of your sport - that's perfectly normal.
• Specific stretches may be required post-injury/post-session
• Slow stretching is normally done separately to the dynamic session

If you want to add tructure you can follow warm-up/injury prevention protocols such as the Fifa_11_english

When it comes to work, posture and stiffness. There is no perfect posture but you can follow the advice online for a guide to you for desk-based setup...

If your body feels tight think movement to raise the temperature and alter the viscoelastic properties of the tissue. Stretching will have short term benefits but you need to look at the bigger picture of how you use/engage the tight structures and correct these issues for long term benefits...