In a word, YES.  But like most things in life, flexibility is a relative term and its importance really depends upon what activities you are performing.  Different activities have very different demands and our bodies respond to our training by improving in the areas that we stress them.  This is called specific adaptation to imposed demands and is really why when we lift weights we get stronger, when we run we get in better cardiovascular and aerobic condition, etc.  Our bodies respond by getting bigger, looser, stronger and more efficient.  Likewise, when we stop training our bodies respond by getting smaller, tighter, weaker and terribly inefficient!

Way back when I was in high school, many of our coaches and trainers didn’t know much about proper flexibility or strength training.  Once I made it to college, there was much more ‘science’ behind what we were doing in the weight room but the stretching piece was still limited to ‘hold…don’t bounce,’ and it seemed the majority of stretching I saw on the field and in training sessions fell into the ‘Passive’ category.   Once in physical therapy school, I learned the benefits of PNF stretching techniques (hold/relax, contract/relax) which is great for one on one or paired stretching but lacks some practicality with large team sports. 

What is ‘Good’ flexibility?  There are standard positions that are used to measure a person’s flexibility and it’s important to have standards so that you can compare each to a ‘normal’ range of flexibility.  However, just because someone falls in the normal range, does that mean their flexibility is ‘good?’  Rather than stretch muscles to perform well on a test, shouldn’t we stretch movements that we’ll be required to make during activity?

Thankfully, strength training has evolved to include more functional patterns and movements due, in large part, to knowledge of specificity of exercise.  More recently, flexibility training has taken the leap into more active range of motion stretching.  The reality is that the best flexibility program includes both passive and active stretching.  Passive stretching has been shown to be beneficial to gaining elasticity in muscle and active range of motion can take advantage of neurological components (overriding the muscle spindle reflex using reciprocal inhibition) to produce greater flexibility and range of motion.

Two or more bones come together to make a joint.  That joint is surrounded by a tough, fibrous capsule that has thicker portions to give the joint stability.  Joints also have strong bands of tissue, called ligaments that hold the bones together.  Any tightness in the capsule or ligaments will restrict the movement, or mobility, of a joint.  Across all joints are muscles that, when they contract or relax, will move the bones through the available range of motion.  If there is tightness in the muscles, the range of motion will be restricted, even if there is enough mobility available.  So, mobility and flexibility are not the same thing but both are very important in our ability to move.

There are little neurological parts in the muscles that are designed to protect your muscles from injury by detecting the rate of change of stretch.  If a muscle is stretched quickly, it stimulates a reflex contraction (this is why bouncing as you stretch is probably not your best bet!)  If a muscle is stretched slowly, the neurological part, called the spindle, is not stimulated and it allows the muscle to continue stretching.  Muscles also work in pairs with one straightening and the other bending.  In order to work effectively, when one is tightening the other is wired to stay ‘off’ so the two won’t be working against each other.  This is called reciprocal inhibition.  Active stretching can take advantage of slow, moving stretches to override the spindle reflex and can also use the muscle opposite the one you want stretched to move your joint through its range of motion to gain flexibility.