Joint Mobility Versus Muscle Flexibility

Which is more important to focus on?  It all depends on your unique body and goals. 

As an athlete, is it better to have mobile joints or flexible muscles?  Well, it depends.  Ultimately, like any training or recovery method, all athletes have specific goals and their bodies are unique.  Hence the one-size-fits-all approach does not apply.  Without getting into the heated and never-ending stretching debate, let’s first discuss the difference between joint mobility and muscle flexibility, and who can benefit from each.  

Ever wonder why someone can’t fully straighten or bend their elbow after being in a cast for four weeks?  Most people think that the muscles are shortened and tight, but it’s actually the joint itself becoming stiff and restricted due to a hypomobile joint capsule.  

Joint mobility refers to a joint’s ability to move freely through a given motion.  A joint can be stiff and thus hypomobile or it may be loose and thus hypermobile.  The amount of mobility in a joint is primarily determined by the pliability and length of the ligaments and joint capsule.  The length and ability of the ligaments and joint capsule to control the joint is determined by genetics, posture, activity, and injury history.  The quality of movement in a joint will determine how well a muscle can lengthen or activate.  A joint can be stretched beyond its “natural” limits unintentionally via a sprain or intentionally to achieve greater motion (i.e. when swimmers stretch shoulders and ankles beyond natural motion).  What is normal or natural joint mobility for a given joint is debatable, although it is generally accepted that a stiff or hypomobile joint should be mobilized to allow for improved motion and muscle activation, while a loose or hypermobile joint should be stabilized through strengthening.  

Muscle Flexibility refers to the muscle’s ability to lengthen over one or two joints.  A muscle is connected to a bone via tendons at two different points on the bone.  Muscles will contract and relax in response to to signals from our brain and nervous systems.  As a muscle reaches its maximum length, tension increases at its attachment points, causing a stretching sensation.  While there are ideal muscle lengths for each muscle, they are more theoretical and must be based on an athlete’s unique anatomy, injury history, and goals.  

Examples of which athletes need what:

  • An athlete who needs joint mobility and muscle length would be a triathlete with Achilles tendinosis.
  • An athlete who needs only joint mobility at one specific location and is otherwise hypermobile would be a cyclist with chronic right side low back pain.  
  • An athlete who needs only muscle length would be a triathlete with low back pain during the run, almost immediately following the bike.