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Stretching and Injury Prevention

Does Stretching Prior to Exercise Reduce the Risk of Injury?

We are all told that we should stretch before undertaking vigorous exercise but does scientific research support this. Pre-workout stretching seems to be a logical thing to do as tight muscles/tendons probably have a greater susceptibility to strain during exercise (when compared with relaxed-flexible soft tissues). However if we stretch are we less likely to get injured? The research evidence is contradictory.

Some studies have found support for the hypothesis, others no difference (and some that stretching prior to a work-out can actually increase the prevalence to injury!). For example in a study of 1543 athletes who ran in the Honolulu Marathon, 47% of all male runners who stretched regularly were injured during a one-year period while only 33% of male runners who didn’t stretch were hurt (1).

ExerciseEven when the research accounted for the fact that the strongest predictor of a future injury is a past injury and excluded runners who had taken up stretching after a previous injury, the stretchers had a 33% greater risk of injury. The stretchers did not run any more miles than the non-stretched individuals.

However, this study also concluded that stretching after workouts reduced the risk of injury. The conclusion was made that stretching must be carried out when muscles are warm (and thus less resistant to being stretched out) to be protective.
In a similar stduy (2) 159 runners were instructed how to warm up, cool down and stretch effectively while a second group of 167 similar runners received no instruction at all. Over a few months, the injury rates of the two groups were identical so the instructed warm-up, cool-down and stretching provided no protective benefit.

However, other studies have found that stretching may be beneficial. A study of military recruits who practised a series of static stretches before and after training were compared to a control group who performed no stretches (3). The stretching group demonstrated a significantly lower rate of muscle-related injuries but no difference in the rate of bone or joint injuries.

In a review of the literature, Thacker et al (4) stated that “There is not sufficient evidence to endorse of discontinue routine stretching before or after exercise to prevent injury among competitive or recreational athletes”.

  
(1) Lally D. ‘New Study Links Stretching with Higher Injury Rates’, Running Research News, Vol. 10(3), pp. 5-6, 1994
(2) van Mechelen W, Hlobil H, Kemper HCG, et al. Prevention of running injuries by warm-up, cool-down, and stretching exercises. Am J Sports Med 1993;21:711-19.
(3) Amoko et al. “Effect of static stretching on prevention of injuries for military recruits.”
(4) Thacker et al. “The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature”. Medicine & Science in Sports & Exercise. 36(3):371-378, March 2004.

PNF Stretching

PNF stretching is considered to be the most effective way to increase static flexibility and is a combination of static passive stretching and isometric stretching. PNF stands for Proprioceptive Neuromuscular Facilitation and was first developed as a treatment for paralysis patients.

PNF stretching is usually carried out with a partner who provides the resistance for the isometric contraction although it can be done without a partner (but generally will be less effective). If using a partner, then it is important that the partner be attentive and focused.

Pnf StretchingThe most commonly used PNF technique is the “Hold-Relax” which is sometimes referred to as the “Contract-Relax”. The muscle is stretched passively towards the limit of its range of motion and then the muscle being stretched is isometrically contracted for 5-15 seconds after which the muscle is relaxed for a couple of seconds before being subjected to a passive stretch which should be greater than the initial passive stretch. This stretch is held for around 10-15 seconds before repeating the PNF stretch one or two more times.

PNF Stretching Examples: Hamstring Stretch
For an example of a PNF stretch, then the person being stretched lies flat on their back with one leg bent at 45 degrees and the other leg extended straight. The partner lifts the straight leg until a comfortable stretch is felt through the hamstring (nb partner just supports the stretched leg and does not push). This stretch is held for 15 seconds.

The stretchee should then isometrically contract the hamstring against partner’s resistance for 5-15 seconds, relaxes and the partner gently guides the hamstring to a deeper stretch. This is repeated a few more times until there is no further increase in range of motion.

Brief PNF Physiology of Stretching
Muscles spindles cells located within the muscles, protect the muscle from injury. They sense how far and fast a muscle is being stretched and when activated produce a stretch reflex. This reflex causes the muscles to contract to prevent overstretching the muscle.

Located within the muscle tendon is another sensor called the golgi tendon which senses how much tension is being put upon the tendon. When the golgi tendon is activated then it relaxes the muscles (unlike the muscle spindle).

A voluntary contraction during a stretch increases the tension on the muscle, activating the golgi tendon organs more than the stretch alone. So when the voluntary contraction is stopped the muscle is inhibited from contracting against a subsequent stretch. PNF stretches uses this to take advantage of the sudden vulnerability of the muscle and its increased range of motion by using the period immediately following the isometric contraction to train the stretch receptors to get used to this new, increased, muscle length. This is accomplished by the final passive stretch.

Some General Recommendations for PNF Stretching

•Leave 48 hours between PNF stretching routines
•For each muscle group complete 2-5 sets of the chosen exercise
•Each set should consist of one stretch held for 10-15 seconds after the contracting and relaxing phases
•PNF is not recommended for anyone under 18 years old
•A 5-10 minute thorough warm up is recommended before performing PNF stretching as a separate exercise session.

While most of us could obtain benefit from the improvement in flexbility that PNF stretching can bring, there is some conjecture amongst sports professionals about the effective of stretching in general to reduce the risk of injuries and to improve performance. Although there is some conflicting evidence reported, on balance research literature reviews such as reported by Thacker et al (1) support the hypothesis that routine stretching has little impact on reducing total injuries amongst competitive or recreational athletes.

  
However, research has also found that pnf stretching may lead to improvements in running mechanics. Caplan et al (2) concluded from studying rubgy league players that stretch training at the end of regular training is effective in improving running mechanics during high velocity running.

As with all stretches, only take a PNF to the limit of what feels comfortable. Pain is an indication that you are overstretching.

In addition, there are advantages and disadvantages of PNF stretching and it may be worthwhile discussing these with a suitably qualified sports therapist.

(1) Thacker SB, Gilchrist J, Stroup DF, Kimsey CD., Jr. “The impact of stretching on sports injury risk: a systematic review of the literature”. Med Sci Sports Exerc. 2004;36:371-378
(2) Caplan N, Roggers R, Parr MK, Hayes PR. “The effect of proprioceptive neuromuscular facilitation and static stretch training on running mechanics.” J Strength Cond Res, 2009, 23: 1175-1180

By Richard Lane

Do you cheat when you stretch your quads?

Many people “cheat” when they stretch their quads. The standard stretch for the quads that you will see many people doing is to stand on one leg and bring their foot to your butt.

However, the chances are that their alignment is such that they are not actually stretching the quads at all, but merely compensating by hip or trunk rotation.

(If you can cope with the sound of young children) The following video explains how best to perform a genuine quad stretch.


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