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Sunday, March 11, 2012

The What, Why, How and When of Flexibility

I have to admit that I'm one of the many people who has a love/ hate relationship with flexibility exercise.  It's boring, uncomfortable and feels like it takes years to hold a stretch for one minute.  If I never learned about the benefits that stretching has to offer, I would have never gotten into the habit of forcing myself to dedicate at least 10 minutes a day to stretching.  Hopefully after learning about the benefits of stretching, you will also decide to start forcing yourself to stretch!

WHAT IS FLEXIBILITY & HOW IS IT MEASURED?
Flexibility refers to the maximum range of motion that a joint or combination of joints can move through.  Range of motion can be measured with a goniometer (see picture below).  Although it seems simple to use, this tool requires in depth knowledge of anatomy to pinpoint the axis of rotation within the joint.  Eyeballing the "approximate" center of the joint is just as useful as guessing without a goniometer.  While personal trainers are not required to measure range of motion with a goniometer, it's an important tool to have if you're the type who wants to know 100% that you're making progress.

One of my most useful tools... a 12" goniometer
HOW TO FIX INFLEXIBILITY: ACTIVE VS. PASSIVE STATIC STRETCHING
When a joint cannot reach normal range of motion, the joint is said to be inflexible.  Performing flexibility exercises helps to increase range of motion through "plastic" or permanent changes.  While there are different variations of stretching techniques, I will cover the easiest/ safest form of stretching, static stretching,  Static stretching can be done actively or passively.  Active static stretching involves holding a stretch by using the agonist muscles to stretch the antagonist muscle groups.  In this form of stretching, no external objects are used to hold the stretch.  Passive static stretching involves the use of an object (Towel, rope, bench, floor, wall, etc.) to help the limb move deeper into a stretch.  Since all forms of stretching has be identified to be effective at improving flexibility or range of motion, whatever you choose to do depends on personal preference (3).  Now comes the big question...

HOW LONG SHOULD I HOLD A STRETCH?
When comparing changes in range of motion between 0, 15, 30 and 60 second stretches, the 30 and 60 second group saw the best results (4,11).  When directly comparing 30 second and 60 second stretches, both durations produced nearly identical improvements.  The 0 and 15 second group showed insignificant to zero gains in flexibility.

While these studies showed that 30 to 60 second static holds produced the best improvements, don't think that as long as you hold a stretch longer than 30 seconds, you're guaranteed to get results.  What these studies won't mention is that the subjects were instructed how to stretch correctly.  This means holding the stretch with the correct form and tension.  Without good form or the right amount of tension, you probably won't see results even with 60 or 120 second holds.  I plan to post instructional videos demonstrating correct form in my YouTube account.  For now, here are some rules you can follow to make sure that you're stretching correctly:
  1. Keep the limbs in correct alignment.  If you're stretching the calf muscle (gastrocnemius/ soleus) group, make sure that the foot is pointing forward and not rotated to the left or right side.
  2. Relax and move into the stretch S L O W L Y.  Without going into the anatomy and function of golgi tendon organs and muscle spindles, the reason why it's important to move slowly and progressively into the stretch is to allow the muscle to relax.  If the muscle isn't relaxed, it will contract and prevent the joint from reaching a meaningful depth to improve range of motion (6,10).
  3. Stretch to the point of a stretch, NOT PAIN.  A good stretch should feel uncomfortable...  If it feels like you're tourturing yourself, back off.
WHEN SHOULD I STRETCH?
After exercise is the best time to stretch for flexibility, but why?  Studies have shown that holding a static stretch for 30 seconds and 100 seconds to 30 minutes can reduce performance.  Specifically, power output was affected the most and trends showed that the fitter the individual was, performance would decrease to a greater extent (1,4,5,7,11).

This doesn't mean that all forms of stretching is bad before exercise.  Compared to a typical warmup, dynamic stretching has been shown to consistently improve muscle performance and power (3,10,11).  Dynamic stretching involves contracting the antagonist muscle group repeatedly through controlled swings or twist.  It's similar to ballistic stretching with the exception that the movements are much slower.

Based on my experience, I feel more springy and quicker after dynamically stretching versus light cycling or jogging.  Cyclists should especially perform a dynamic warmup since it's primarily a lower body exercise.  I've seen countless numbers of cyclists who never warmup the entire body- they just hop on the bike and go.  This leaves the upper body in the cold and not 100% ready to take on unexpected maneuvers.


WHY IS IT IMPORTANT TO BE FLEXIBLE?  TWO REASONS
  1. Good flexibility allows the body to maintain good posture naturally.  Posture is listed as number one because in virtually any situation, bad posture is a main contributor to injury and pain.  In sports and everyday life, one of the biggest complaints reported by athletes and non-athletes is lower back pain.  In many cases, lower back pain is caused by the tilt of the pelvis which affects the curvature of the lumbar spine.  When the pelvis is tilted too far forward or back, this causes the discs of the lumbar spine to compress and place damaging forces onto the intervertebral discs.  While lower back pain is a common problem, inflexibility can also contribute to other problems related to the foot, ankle, knee, hip, thoracic spine, shoulder complex and the cervical spine.  Full posture and range of motion assessments are the easiest ways to determine the root cause of pain related to inflexibility. 
  2. Improves the storage of elastic energy at the tendon and muscle:   For anyone looking for an exercise to increase explosive power for improved running economy or cycling performance, flexibility is a major underdog that can definitely help.  It has been studied and accepted that as a result of flexibility training, the amount of elastic energy stored in the muscles and tendons improves significantly.  This means that less chemical energy (from carbohydrates, fats and protein) is needed to do the same amount of work- so you save energy which can be put towards more important things like sprinting to the finish line or breaking away from the group.

DOES STRETCHING PREVENT OR REDUCE MUSCLE SORENESS?
You might be wondering why "relieves muscle soreness" is not on the list.  It appears that although stretching was advocated heavily in the past (1980's) to reduce muscle soreness, more recent studies found that stretching does not reduce delayed onset muscle soreness (4,8,9).  So what is the best way to relieve muscle soreness?  This is still a question without a definite answer, but expect to see more research geared towards finding the best method of recovery- light aerobic exercise, compression clothing, cold therapy or massage. Based on the several self reports claiming that light exercise speeds recovery, I recommend it because it makes sense from a physiological standpoint.  By lightly circulating blood around the damaged muscles, the blood helps to remove waste products and transport cells/ nutrients necessary for repair.  Just make sure that you're actually recovering and not going hard!

REFERENCES:
  1. Behm, D.G., D.C. Button, and J.C. Butt. Factors affecting force loss with prolonged stretching. Canadian Journal of Applied Physiology. 26:261-272.2001.
  2. Biering-Sorenseu, F.: Physical measurements as risk indicators for low-back trouble over a one year period. Spine. 9(2):106–119 (1984).
  3. Bloomfield, J., Timothy R. Ackland, and Bruce Elliott. Applied anatomy and biomechanics in sport. Melbourne, Australia: Blackwell Scientific Publications, 1994. Print. 
  4. Brandy, William, and Jean Irion. "The Effect of Time on Static Stretch on the Flexibility of the Hamstring Muscles." Physical Therapy 74.9 (1994): 845-850. Print.
  5. Cornwell, A., A.G. Nelson, G.D. Heise, and B. Sidaway. Acute effects of passive muscle stretching on vertical jump performance. J. Hum. Mov. Studies 40:307-324.2001.
  6. DeVries H. (1986) Physiology of Exercise - For Physical Education and Athletics, pp. 462-472, 474-487, 482-488/ Wm C. Brown Publishers, Dubuque, IA, USA.
  7. Fowles, J.R., D.G. Sale, and J.D. Macdougall. Reduced strength after passive stretch of the human plantarflexors. Journal of Applied Physiology. 89:1179-1188. 2000.
  8. Herbert, R. D., & M. Gabriel: Effects of stretching before and after exercising on muscle soreness and risk of injury: a systematic review. British Medical Journal. 325:468–470 
  9. (2002). Herbert, R. D., & M. de Noronha: Stretching to prevent or reduce muscle soreness after exercise. Cochrane Database of Systematic Reviews 2007, Issue 4. Art. No. CD004577. DOI: 10.1002/14651858.CD004577.pub2.
  10. Plowman, Sharon A., and Denise L. Smith. Exercise physiology for health, fitness, and performance. 3rd ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2011.
  11. Yamaguchi, Taichi, and Kojiro Ishii. "Effects of static stretching for 30 seconds and dynamic stretching on leg extension power." The Journal of Strength and Conditioning Research 19.3 (2006): 677-683. Print.