Tip of the Month -- Feb. 2006 

Flexibility Basics

By Michael Irr

One general definition of flexibility held by many in the scientific community is the ability of a joint to move freely over its full range of motion (ROM).  Flexibility is determined by three physical characteristics: 1. skeletal muscle, 2. tendons, and 3. fibrous capsules/fascia.  Neuromuscular activation, via the central nervous system (spinal cord and brain), also plays a role in certain aspects of flexibility.  Each of the physical characteristic carries different mechanical properties that are altered during stretching.  Muscles have primarily elastic qualities and will therefore return to their original position after completing a stretch.  Connective tissues (like tendons and ligaments) have both elastic and plastic qualities, so if stretched for a significant period of time (30-90 sec.) they will remain in their deformed state.

Coaches use flexibility in their programs for two primary reasons, warm up/cool down and to increase ROM across a joint, especially when that joint’s performance is hindered by its ROM.  For example, athletes with tight hamstrings may find it difficult to sit back in a squat to hit parallel, so stretching the hamstrings may help with that movement.  There are four basic types of stretching that strength coaches and other sports medicine professionals use to increase flexibility.  Static stretching, or the typical reach and hold, for an allotted amount of time (usually 30-90 sec) is one way to elongate muscle.  Proprioceptive neuromuscular facilitation (PNF) stretching generally involves contraction-relaxation of opposing muscles to increase flexibility.  Both static and PNF methods are typically used to create plastic changes in an athlete.  During warm ups, ballistic stretching can be used that involves bouncing or bobbing in rapid succession.  Also, the dynamic stretching technique usually involves movements that are the same as ballistic stretching, but slower and more controlled.  One primary goal of ballistic and dynamic routines is to increase muscle temperature making them integral for warm ups.  Also, ballistic and dynamic stretches are more elastic so the muscle will not stay deformed, which research shows is important for force production. 

One common myth that people believe is that stretching will reduce injury.  In theory it seems possible the ability to get into flexible positions would reduce injury, but no scientific study has supported this concept, mostly because it would be hard to evaluate and perform such a study.  Regardless, it is the opinion of top scientists that “fitness levels,” like strength and endurance, may be better indicators of reducing potential injury.  Without throwing flexibility completely out the window, “functional ROM” becomes important, or the ability to show strength in stretched positions (for example, strength at the bottom of a deep squat). 

Of course, one main strength and conditioning concept will always remain constant, “if you don’t use it, you’ll lose it.”  If flexibility is not practiced, there is no way to get better.  Also, after ceasing flexibility routines, athletes will probably return to their previous levels of flexibility over time.  For example, an injured athlete who has been immobilized with a cast will be extremely stiff once the cast is removed.

Nobrega, et al.  “Interaction Between Resistance Training and Flexibility Training in Healthy Young Adults.” JSCR, 2005.

Fleck, Kraemer.  Designing Resistance Training Programs.  Human Kinetics, 2004.