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Introduction

Although there is little proof that stretching reduces injury, there are many other benefits of performing stretches. From reducing muscle related discomfort in the workplaceto increasing sports performance2 . Our therapist Kiri Norton looks into the benefits of stretching.

What is flexibility?

Flexibility is the ability to move the arms legs and trunk freely throughout a full, non-restricted pain free range of motion3. An individual, who is inflexible, is highly susceptible to pulling a muscle. Whereas an individual who is highly flexible e.g. a gymnast, then their range of movement at their joints is excessive which causes instability of the joint thus making them more susceptible to injury. Therefore having a flexibility level that is in-between these two examples is the most beneficial.

What types of stretches are there?

Hip flexor stretch

Stretching falls into 4 different categories; static, dynamic, ballistic and proprioceptive neuromuscular facilitation (PNF).

Static:

Static stretching is a passive stretch given to the antagonist muscle by placing it in a maximal position if stretch and holding it there for a period of time. E.g. holding your foot to your bottom to stretch the quadriceps.

Dynamic:

Dynamic stretching is stretching the muscle whilst movement is taking place, e.g. lunges.

Ballistic:

Ballistic stretching is a technique that uses a bouncing motion to force the area beyond its normal range of movement. The bouncing technique causes repetitive contractions of the agonist muscle and produces quick stretches of the antagonist muscle e.g. bouncing up and down repetitively to try and touch your toes, pushing further at each bounce).

PNF:

PNF is a group of manually strengthening and stretching techniques. E.g. contraction of agonist (stretched muscle) followed by further stretch (possibly with contraction of antagonist). Contract- relax, hold-relax.

What are the physiological benefits of stretching?

  • Increased range of movement; This is beneficial as it can help with good posture as well as improving the quality of life of individuals as the performance in everyday activities becomes more efficient4.
  • A muscle trigger point (knot) can be caused by a chronically irritated muscle spindle. Stretching can help reduce trigger points. Slow stretching increases the metabolism in the muscle spindle, this elevates its oxygen consumption allowing it to relax and cause the trigger point to reduce5.
  • Increases blood supply to the soft tissues; this is beneficial to those with muscular injuries as it will bring nutrients to the area (Abelson, 2005).
  • Reduces tension and resistance in muscle tissue 6  
  • Increases comfort and performance of your body6  
  • Can reduce pain in musculoskeletal injuries that involve muscle tightness 6  

Limiting Factors

Every individual has a different range of motion which they were born with at each joint. Berardi7 states that Occupational demands, movement demands and training oversights are limiting factors for flexibility. Generally, limiting factors can be spilt into internal and external factors.

Internal factors:

  • The length and integrity of the joints, muscles, tendons and ligaments can affect flexibility.
  • Movement demands like range of motion, strength and endurance.
  • Training oversights is when the body is overused; If the body is overused then the structures become tight, weak and irritated which in turn, reduces range of motion7.

External factors:Hip flexor stretch

  • Cold weather
  • Age (tissue and collagen changes)
  • Gender
  • Clothing
  • Equipment
  • Surfaces and lack of appropriate shoes (Berardi, 2005)

Things to be aware of when stretching

  • Static stretching can reduce your strength and power output, if your sport involves powerful and explosive movements e.g. high jump then PNF stretching is more suited to you 8
  • Over stretching can be detrimental. Over stretching is usually caused by stretching to the point where pain is felt. This could predispose you to an injury and even cause nerve damage
  • Holding a stretch for too long can give way to an injury10
  • Lack of flexibility in one joint can affect the entire kinetic chain. E.g. an individual with tight hamstrings may compensate for this by changing their gate -Hitching hip, using the quads more.

Physiology of stretching

When stretching, this stimulates the stretch reflex mechanism. This involves 2 types of receptors:

  • The muscle spindles which are located in the muscle belly. The muscle spindles job is to detect the stretch of the muscle
  • Golgi tendon organs (GTO’s) which are located within the tendon of the muscle. GTO’s job is to detect tension within the muscle.
  • There is a third type of proprioceptor, called a Pacinian corpuscle. These are located close to the GTO’s. They are responsible for detecting the change in movement and pressure11.

Stress-relaxation is associated with an increase in presynaptic inhibition of the sensory signal from the muscle spindle. This occurs with inhibition of the release of a neurotransmitter from the synaptic terminals of the muscle spindle Ia fibres that limits the activation in that muscle therefore allowing the muscle to stretch further. It is also said the stretching disrupts the actin-myosin bonds with in the intrafusual fibres of the muscle spindle which reduces there sensitivity to stretch.

Autogenic inhibition is defined as inhibition mediated by afferent fibres from stretched muscle acting on the alpha motor neurones supplying that muscle, causing it to relax. Prentice (2010) suggests that a contraction of 6 seconds is long enough for this to occur as the GTOS override the impulses from the spindles. As stress relaxation occurs the muscles will elongate further each time, producing creep.

The lengthening of the muscle via stretching allows for viscoelastic and plastic changes to occur in collagen and elastin fibres. The viscoelastic changes are temporary but the plastic changes although difficult to achieve, result in permanent change in length due to deformation. This can be created by long periods of stretching. Lengthening of the muscles occurs when a stretch is held for a prolonged period of time. This is because as you hold the muscle in the stretched position, the muscle spindle then becomes accustomed to the new length 12.

Deformation is not desired in most sports like high jump, where power is needed. But in a sport like dance or gymnastics, it is important for the movement to be aesthetically pleasing, therefore plastic deformation is beneficial to dancers as they need a lot of flexibility. But along with this comes its downfalls, as it can increase the risk of injury as the muscle is closer to its point of failure.

There is also a protein in the muscle called Titin. It looks like a coiled spring, as you stretch it uncoils therefore allowing you to have increased flexibility. But it can coil back again and is not permanent. Therefore stretching regularly can keep the Titin proteins uncoiled.

References:

1. DeCosta, B. & Vieira, E. (2008) Stretching To Reduce Work-Related Musculoskeletal Disorders: A systematic Review, Journal of Rehabilitation Medicine, 40, p. 321-328.

2. Shrier, I. (2004) Does Stretching Improve Performance?: A Systemic and Critical Review of Literature, Clinical Journal of Sport Medicine, 14 (5), p. 267-273.

3. Prentice, W, E. (2010) Rehabilitation Techniques in Sports and Medicine, 5th edition, Mcgraw Hill, London.

4. Barratt, M. (1964) Foundations For Movement, Dubque, IA: Wm. C. Brown Co.

5. Porter, M. (1998) The New Equine Sports Therapy The Blood Horse Inc. USA

6. Abelson, B & Abelson, K, T. (2005) Kinetic health [ONLINE] available at: http://www.drabelson.com/PDF/Stretching%20%20Checkup%20Mag%20Article%20-%202005.pdf

7. Berardi, G.(2005) Finding Balance. 2nd ed. Routledge, NY: Routledge. P. 34-37

8. Simic, L., Sarabon, N. and Markovic, G. (2013) Does Pre-exercises static stretching inhibit maximal muscular performance? A meta-analytical review. Scandinavian Journal of Medicine & Science in Sports, 23, p. 131-148

9. Yessis, M. (2006) Runners Need Active Stretching, AMAA Journal Winter, 18 (2), p. 8-18.

10. Blakey, W, P. (1994) Stretching Without Pain. Canada: Twin Eagles Educational & Healing Institute, P. 20.

11. Appleton, B (1996) Stretching and Flexibility – Everything you never wanted to know Massachusetts Institute of Technology website.[ONLINE] Available at: http://web.mit.edu <accessed:20/12/16>.

12. Scully C (2002) Equine Sports Massage – Study Notes ACATT. Victoria

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