Stretching, Should You Stretch?

Stretching

Static stretching (SS) has been used as part of a warm up protocol for many years. It is common to see teams of every code, athletes, cyclists, etc, stretching before their chosen discipline. It is also common among all levels of athletes to incorporate SS into their cool down regime. This methodical approach has been indoctrinated into us for many years by well meaning parents, coaches, teachers, etc.  However there is very little evidence to show the benefits of stretching. The supposed benefits of static stretching (SS) are to:

• Prevent injury
• Improve flexibility
• Enhance performance.

Throughout this post I will look at each of these supposed benefits in light of what the evidence says. I will then give an alternate way to achieve these benefits were the evidence for SS is lacking.

 

Static Stretching and Injury Prevention

This is probably the most well ingrained belief we have about stretching and why we stretch. Often after an injury has settled and you return to play you may feel a bit tight or less flexible. You feel if you just stretch out for a few minutes pre/post exercise, that you’ll in some way keep on top of the old injury and the muscles and tendons will be more pliable.

The rational for why stretching may aid injury prevention is held in the belief that stretching has an affect on the compliance and stiffness of the tendon. The stiffer the tendon the less energy it can absorb which increases stresses on the muscle its attached to and hence you get injured. Therefore a less stiff tendon is more compliant, it can store more energy and reduces stress on the muscle. (Witvrouw et al,  2004), (Safran et al, 1989), (McHugh et al, 1999).

However other authors have found no mechanical changes/stiffness in the musculotendonious unit (MTU). In a recent study, Morse et al, (2008) stated , “decrease in MTU stiffness following repeated stretches, such as those used by athletes during warm-up, is not due to a change in the tendon but rather to an increased compliance of the proximal, muscular, portion of the MTU. This increased compliance of the muscle is not, however, fully explained by a change in the extensibility of the muscle fascicles and we propose that connective tissue elements within the muscle change their elastic properties when subject to repeated stretches”. What this implies is that there is no change in the tendon stiffness, rather more compliance. From above, tendon stiffness is related to energy absorption and stresses placed on muscles. Therefore if we can’t change the stiffness of the tendon by stretching we can’t reduce the stresses placed on the muscle?

In addition to this, in a randomised control trial of 1538 male army recruits, Pope et al, (1999) found no relationship with injury prevention and pre-exercise stretching, stating, “preexercise muscle stretching does not produce a clinically worthwhile reduction in the risk of lower-limb injury”.

 

Static Stretching and improved flexibility

There is a lot of evidence to suggest that static stretching increases flexibility (O Sullivan et al, 2009, de Weijer et al, 2003, Brady et al 1997, Power et al 2004) in the short term. The consensus on how it achieves this is  lacking. One possible way in which this may be achieved is through an increase in the total length of the MTU, where the muscle fascicles increase by the same amount as the tendon during the stretch, with the former retracting less post stretch, (Morse et al, 2008). This would lead to a net increase in length of the MTU. Other studies (Magnusson et al , 2000) suggest a in change in the visioelastic properties of the MTU leads to in increase in overall length of the MTU. Regardless of which theory is correct, flexibility and range of movement are increased in the short term with static stretching. I say short term as this increase in flexibility doesn’t last long. In fact dePino et al, (2000) found that after 4 consecutive stretches of 30 sec on the hamstring muscle, the increased flexibility only lasted 3 minutes. O Sullivan et al, (2009) found that after a 5 minute jog warm up and 3 *30 second static stretches, flexibility increased in the hamstring muscle.  However this increase reduced after 15 minutes rest. Therefore what we get from this is that stretching can increase flexibility but it doesn’t last long. Increased flexibility would have us believe that this means enhanced performance or reduced injury risk. However the relationships of flexibility injury risk and enhanced performance is precarious.

 

Static Stretching and Enhanced Performance

In a recent study, Haddad (2014) found that static stretching had a negative effect on performance for up to 24 hours post stretch. Their objective was to compare the effects of static vs dynamic stretching on explosive performance, and repeated sprint ability after a 24-hour delay. They found that 10, 20, 30m sprint performances were better after a dynamic stretching protocol than a no stretching control group and a static stretching group. They also found that horizontal jumps were better in the dynamic stretching group. In light of this, the authors recommend to avoid SS for up to 24 hours pre-explosive activities.

In addition to this, a 2012 meta-analytical review of the literature on whether static stretching inhibits maximal muscular performance found, “clear evidence from 104 studies that a pre-exercise static stretching induces significant and practically relevant negative acute effects on maximal muscle strength and explosive muscular performance, regardless of age, gender, training status.”  They also recommend that based on this study static stretching as a sole warm-up should be avoided.

What this means is that SS had no benefit on performance. However there is evidence which suggests SS for shorter duration have a less negative effect, (Young et al, 2006).

The consensus for SS prior to endurance type activities is lacking, with some studies showing negative effects, (Wilson et al, 2010) while others showing no effect (Mojock et al, 2011). Interestingly, the evidence for increased endurance performance following static stretching is almost nill.

 

Summary Points:

• Static stretching has no effect on injury prevention.
• Static stretching does increase flexibility but it is short lived.
• Static stretching has been shown to have no effect or a negative effect on performance.

In light of this it is hard to see why we should continue to perform static stretches prior to activities which demand speed, power, strength or endurance. Static stretching may be beneficial with activities in which the goal is to increase range of movement (dancing, gymnastics).

An alternative to the goals of SS can be attained through eccentric strength training. Eccentric strength training has been shown to increase performance, (Friedmann-Bettae, et al 2009), (Cormie et al, 2010) endurance, (Aagaard, et al 2010), (JaeHo et al, 2013), (Gremeaux et al, 2010) flexibility (O’ Sullivan et al, 2012) and prevent injury (Peterson et al, 2011).

 

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