What Does Stretching Actually Do?

By Elliot Fisher

 

Recently stretching and mobility work has become a popular topic.  It’s been advertised to be the key to injury prevention, rehabilitation, increased performance, and longevity.  Stretching is important but may not be the cure all it is hyped up to be.  In this article, we’ll look at the actual benefits of stretching.

 

Stretching is the act of putting a load on a muscle (elongating it) in order to enhance the range of motion (ROM) of the tissue.¹ The ROM is the degrees of freedom from a starting position to an end position for any angular motion of a joint.  This can be measured using goniometry, which is basically a fancy protractor.  ROM is important because we need a certain ROM and mobility for specific activities.  For example, picking a box off the ground is going to need either a lot of hip flexion (bending over) with some knee flexion (knee bending) or a lot of knee flexion with some hip flexion.  If you do not have this mobility or are limiting ROM at one of the joints, the task will be more difficult and become more dangerous.  With limited ROM or mobility injury risk will increase as if you push a tissue into a ROM that it doesn’t have it will eventually start to give and you will strain or tear the tissue.¹ This is why a lot of people strain their hamstrings (due to the lack of hamstring ROM).  This can also be caused by weak muscles (weak hamstrings in the previous example) but that topic will be set aside for another blog.

 

ROM is specific for the activity being done.  A football player and a gymnast will have different mobility requirements dictated by their activities.  For the average individual, there are certain ranges of motion that are important for activities of daily living (ADL).  Often, individuals will have restrictions in these ROM.  The example used before is tight hamstrings, most people cannot create 90 degrees of hip flexion with a neutral spine (no lumbar flexion or rounding).

 

A list of positions with approximate ROM for each joint are listed below^2,3:

• Hip Hinge (90° Hip Flexion, 180° Knee Extension, Spine Neutral)
• Full Squat (135° Knee Flexion, 135° Hip Flexion, 20° Ankle Dorsiflexion, Mild to Moderate Spinal Flexion)
• Lunge (Back Leg 90° Knee Flexion, 180° Hip Extension.  Forward Leg 90° Hip Flexion, 90° Knee Flexion)
• Arms Overhead (180° Shoulder Flexion)
• Shoulder Internal Rotation (about 90° Shoulder Internal Rotation while Shoulder is at 90° Abduction)
• Shoulder External Rotation (about 90° Shoulder Internal Rotation while Shoulder is at 90° Abduction)

 

The next step is to assess how and when to stretch or mobilize a tissue.  The minimum duration is around 30 seconds of stretch for an increase in ROM, however you can do more up to about 2 minutes to get more of an advantage.^4,5

 

Forms of flexibility and mobility work to consider:

 

Static Stretching

Static Stretching is taking a muscle and passively lengthening it for a period of time.  For example, lying on your back and having someone stretch the hamstrings by flexing the hip (bring the leg up).  This should be done after your workout or away from your workout as it can interfere with the maximum power output.⁶ One exception to this is if you have very limited ROM and need to acutely increase the ROM of a muscle before lifting for safety reasons.  For example, if you can only dorsiflex (bringing the knees over the toes) your calves 5 degrees and stretching helps you get to 10 degrees it might be advantageous to stretch the calves before squatting.

 

 

Foam Rolling and Myofascial Release

Also, myofascial release, foam rolling, and massage can help with increasing ROM.⁷ This can be done before working out as it doesn’t seem to impair performance much, additionally there is some evidence that foam rolling works better acutely than it does chronically.⁸ This makes foam rolling better for pre-workout ROM increases than post-workout.  Additionally, using a ROM especially under load seems to be the best way to achieve and keep ROM.  So, lifting or doing any activity where you are putting yourself in these deeper ROM will help you maintain them rather than just stretching and foam rolling.

 

Proprioceptive Neuromuscular Facilitation (PNF)

PNF stretching is a quick way to increase ROM by relaxing the nervous system.¹ It is performed by making the stretched muscle also create force which allows it to then stretch further after the voluntary contraction.  Typically, this is done by stretching for 30 seconds, contracting the muscle for 5 seconds, stretching for another 30 seconds (deeper than before), and repeating.  There are other forms of PNF stretching but this is the most common.

 

Joint Distraction/Mobilization

You can also mobilize a joint by distracting it (traction force) or mobilizing the joint (putting a slight traction force on a joint and then moving it back in forth or pushing it in one direction).^2,3 This can be done with a band (placing a band around a joint and having it also attached to a stable surface) or with a clinician manually pulling and pushing the joint.  For specific examples, googling banded joint distraction or mobilization will have a list of exercises and demonstrations.

 

In conclusion, flexibility and stretching are not going to be the end all be all to injury prevention and rehabilitation, but it is still very important.  Most individuals are limited in many ranges of motion for ADL and should work consistently overtime to gain appropriate flexibility and mobility.

 

 

References:

 

1. Houglum, Peggy A. Therapeutic Exercise for Musculoskeletal Injuries 3rd Edition. Human Kinetics, 2010.

 

2. Starrett, Kelly, and Glen Cordoza. “Becoming a supple leopard.” The ultimate guide to resolving pain, preventing injury, and optimizing athletic performance.  2nd ed.  (2015).

 

3. Starkey, Chad, and Sara D. Brown. Orthopedic & Athletic Injury Examination Handbook. FA Davis, 2015.

 

4. Bandy, William D., and Jean M. Irion. “The effect of time on static stretch on the flexibility of the hamstring muscles.” Physical therapy 74.9 (1994): 845-850.

 

5. Cipriani, Daniel, Bobbie Abel, and Dayna Pirrwitz. “A comparison of two stretching protocols on hip range of motion: implications for total daily stretch duration.” The Journal of Strength & Conditioning Research 17.2 (2003): 274-278.

 

6. Bacurau, Reury Frank Pereira, et al. “Acute effect of a ballistic and a static stretching exercise bout on flexibility and maximal strength.” The Journal of Strength & Conditioning Research 23.1 (2009): 304-308.

 

7. Junker, Daniel H., and Thomas L. Stöggl. “The foam roll as a tool to improve hamstring flexibility.” The Journal of Strength & Conditioning Research 29.12 (2015): 3480-3485.

 

8. MacDonald, Graham Z., et al. “An acute bout of self-myofascial release increases range of motion without a subsequent decrease in muscle activation or force.” The Journal of Strength & Conditioning Research 27.3 (2013): 812-821.