Sports Medicine: Just the Facts

CHAPTER 69 • CORE STRENGTHENING 413

3. An efficient core allows for maintenance of the
   normal length–tension relationship of functional
   agonists and antagonists, which allows for the
   maintenance of normal force–couple relationships
   in the lumbopelvic hip complex (Clark, Fater, and
   Reuteman, 2000).
   •Why are they important?


4. When a limb is moved, reactive forces are imposed
   on the spine acting in parallel and opposing those
   forces producing the movement (Bouisset and
   Zattara, 1987).


5. The spine is particularly prone to the effect of these
   reactive forces due to its multisegmental nature
   and the requirement for muscle contractions to
   provide stability of the spine (Panjabi, 1992).


6. Without muscular support and contraction, buck-
   ling of the spine occurs with compressive forces of
   as little as 2 kg (Morris, Lucas, and Bresler, 1961).


7. Significant microtrauma of the lumbar spine will
   occur with rotation of as little as 2°(Gracovetsky,
   Farfan, and Helleur, 1985).


8. The musculature of the spine has been shown
   repeatedly to be most important in maintaining
   spinal stability under various conditions (Gardner-
   Morse, Stokes, and Lauble, 1995; Solomonow et al,
   1998).


9. Function of core muscles: oppose the movements
   of limbs, hold spine together, and decrease lumbar
   shearing


10. Muscle dysfunction in low back pain is a problem
    with motor control in the deep muscles related to
    segmental joint stabilization (Richardson et al,
    1999).


11. Back pain can occur as a consequence of deficits in
    control of the spinal segment when abnormally
    large segmental motions cause abnormal deforma-
    tion of ligaments and pain-sensitive structures
    (Panjabi, 1992).
    a. Loss of joint stiffness
    b.Increase in mobility and abnormal spinal motion
    c. Changes in the ratios of segmental rotations and
    translations

WHAT ARE CORE MUSCLES?ANATOMY/
BIOMECHANICS OF THE “CORE”

• Local paravertebral-multifidi
  
  
  1. Stabilizing role: Protecting articular structures,
     disks, and ligaments from excessive bending,
     strains, and injury
  
  
  2. Multisegmental column is unstable and will buckle
     under compression at individual joints unless
     locally stabilized.
     3. Short muscles provide local support for longer
     muscles to work (Bergmark, 1989).
     4. Neutral zone control: Little resistance by passive
     spinal restraints (ligaments).
     a.Sensitive region for stabilization of joints
     (Panjabi, 1992)
     b.Multifidi contribute to control of the neutral zone
     (Panjabi, 1991; Steffen, Nolte, and Pingel, 1994;
     Wilke et al, 1995)
     c. Contribute more than 2/3 of stiffness increase at
     L4–L5 (Wilke et al, 1995).
  
  
  
  


• Polysegmental: Erector spinae
  1.Important for posture: Contract intermittently
  during the swaying movements that take place
  from an upright position.

2. Contraction of the erector spinae extend the trunk,
   a movement controlled largely by opposing activ-
   ity of the rectus abdominus.


3. In slow trunk flexion movements, the erector
   spinae lowers the trunk into flexion (eccentrically
   contract) against the action of gravity during slow
   movements (Oddsson, 1990).


4. Role: Balance external loads and minimize forces
   on the spine (Bergmark, 1989).


5. Only a very small increase in activation of the
   multifidi and abdominal muscles required to
   stiffen the spinal segments—5% maximal voluntary
   contraction(MVC) for ADLs and 10% MVC for
   rigorous activity (Cholewicki, Juluru, and McGill,
   1999).


6. Endurance of muscles to maintain stability margin
   of safety, not absolute strength is most important
   (McGill and Norman, 1987).

• Abdominals: transversus abdominus(TrA), internal,
  external obliques, and rectus abdominus

1. Contraction of abdominals (esp TrA) the pelvic
   floor and diaphragm correlate closely with
   increased abdominal pressure in a variety of pos-
   tural tasks (Cresswell, Oddsson, and Thorstensson,
   1994; Hodges et al, 1997).


2. TrA: Critical in stabilization of lumbar spine
   (Cresswell, Oddsson, and Thorstensson, 1994).


3. Contracting TrA increased intra-abdominal pres-
   sure and tensions thoracolumbar fascia.


4. Helps create rigid cylinder enhancing stiffness of
   lumbar spine (McGill and Norman, 1987).


5. Rectus abdominus and oblique abdominals are
   activated in direction-specific patterns with respect
   to limb movements, thus providing postural sup-
   port beforelimb movements (Aruin and Latash,
   1995; Hodges and Richardson, 1997).


6. Contraction increasing intra-abdominal pressure
   occurs before initiation of large segment move-
   ment of the upper limbs (Hodges et al, 1997).