Flexibility – Not All It’s Cracked Up To Be

Thank you Dr. James L. Nuzzo for writing The Case for Retiring Flexibility as a Major Component of Physical Fitness ¹.  Some of you may be surprised by the title and content, since many reputable sport science and health organizations continue to promote flexibility.  On the other hand, most of my colleagues and former classmates are more likely to be frustrated that there is a need for the article to be published because we’ve known for a long time that more flexibility is not necessarily better.  Whether from an injury risk perspective or for peak performance, too much flexibility is as as bad as too little. 

When doing my undergrad degree at the turn of the millennium, stretching was considered important.  By then, we had moved on from employing static stretches in warm-ups —plentiful research had shown how they hindered speed, force, power, and endurance— but still believed flexibility was important as a performance enhancement and injury reduction tool.  So, early in to my strength & conditioning coaching career, I collected and refined a catalogue of the best static stretches for each muscle ².  I was insistent on my athletes finishing each session with a battery of static stretches to hit every part of the body.  I was and still am proud of the acute relaxation experienced, along with acute and chronic increases in muscle length they achieved.  

However the data we were collecting on flexibility’s effects on performance and injuries of our athletes was not as favourable.  At this time, published research on the lack of benefit —and likely detriments— from chronic stretching, and from excessive muscle lengths was also beginning to accumulate.  

For the players and coaches, it was a reluctant transition away from emphasizing flexibility.  Admittedly, the process was slowed by my own pride and insecurities.  It is not just that humans are change-averse and have difficulty accepting that a long-held belief is baseless.  Many athletes also feel (and some may perform) a bit worse when they first stop stretching, and it takes them a few weeks to get over the hump.  Doubt and other emotions are surely impacting their psychology, yet biochemical factors may also be at play:  Because there is a neurotransmitter release from stretching stimuli, it is possible that cessation results in a mild form of clinical withdrawal.  Regardless of why it may get worse before it gets better, the overall competition/periodization schedule must be considered when choosing when to transition away from static stretching.

Once the concept of optimal flexibility (and a drastic reduction in stretching activities) had been fully embraced by everyone, our athletes got faster —a lot faster.  Sprains and strains became so rare there were no longer enough to show patterns or trends in the data we were collecting.

Dynamic flexibility is a bit different, as pointed out by Dr. Nuzzo.  If you actively contract the muscles through the optimal range of motion, dynamic flexibility exercises can be great for warm-ups and may even be appropriate parts of technical or athletic training sessions.  Notice, I used the term “optimal” again: more is not necessarily better. 

What is the optimal amount of flexibility?  

As we teach in the Foundation course, the optimal length length for each muscle depends on what action it is being asked to perform and is influenced by individual differences in skeletal proportions.  Three things are at play: 1) Overlap of the actin-myosin cross bridges and the length-tension relationship for force production.  2) The number of sarcomeres in series for maximal contraction velocity.  3) The stretch-shortening cycle for high frequency repetitions, and reduced fuel demands (movement efficiency).

It is unlikely all three factors coincide with one another, so a balance must be struck based on the demands of the sport —with priority given to the actions that that matter the most, of course.  It is not straightforward.  A profound understanding of functional anatomy is necessary along with variations in skeletal proportions among players.  A thorough analysis of sports data, biomechanics, metabolic requirements, and neuromuscular demands are also required before answering the question ³.

Remember that more flexibility is not necessarily better for health, performance, or injury risk.  You may be harming your players by trying to increase their flexibility.  So until you learn how to determine what is optimal and how to train them to achieve it ⁴, you should probably avoid wasting time and energy on something that you do not know whether it is helping or hurting each of your players.

-CG