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1. Lower Extremity Consequences of “Core Dysfunction”
Joseph M. Hart, PhD, ATC
University of Virginia
2. Introduction “Core stability may provide several benefits to the musculoskeletal system, from maintaining low back health to preventing knee injury”
Willson J D, Dougherty C P, Ireland M L, and Davis I M, Core stability and its relationship to lower extremity function and injury. J Am Acad Orthop Surg, 2005. 13(5): 316-25.
3. What is the “core”? What is “core stability”?
4. Where is the “core” Lumbo-pelvic-hip complex
Includes the active & passive structures that either produce or restrict movements of the lumbar, hip or pelvic segments
5. What is the “core”? Movements/ stability occurs in 3 planes
6. What is the “core”? Sagittal Plane stability
Co-contraction causes trunk stiffness and raises intra-abdominal pressure
7. What is the “core”? Movements/ stability occurs in 3 planes
8. What is the “core”? Frontal Plane
Glut med., glut min. (1º lateral hip stabilizers)
Unilateral: ipsilateral pelvis elevation
Contralateral: spine stiffness
Perhaps best suited for spine stability; active during nearly all upright tasks
Hip adductors (magnus, longus, brevis, pectineus)
9. What is the “core”? Movements/ stability occurs in 3 planes
10. What is the “core”? Transverse Plane stability
glut max., glut med.
11. What is the “core”? Thoraco-Lumbar Fascia
Covers and inter-connects muscles and fascia surrounding the spine
Helps create a stabilizing “corset” effect
Provides connective support from LE to UE
Allows for integrated kinetic chain activities
12. What is “core stability”
13. What is “core stability” “The ability of the Lumbo-pelvic-hip complex to prevent buckling of the vertebral column and to return it to equilibrium following perturbation”
Coordination and co-contraction of muscles provides spine stiffness
14. What is “core stability” “…the ability to control the position and motion of the trunk over the pelvis and leg to allow optimum production, transfer and control of force and motion to the terminal segment in integrated kinetic chain activities.”
Kibler W B, Press J, and Sciascia A, The role of core stability in athletic function. Sports Med, 2006. 36(3): 189-98.
15. What is “core stability” Core stability is “instantaneous”
Must continually adapt to changing postures and loading conditions
Ensure integrity of spine and provide stable base for movement of extremities.
Absorb forces transmitted through the lower extremity during activity
16. Importance of core stability Mechanical base for motion of the distal segments
Many extremity prime movers attach to the core
Core muscles are active before initiation of extremity movement.
“Proximal stability for distal mobility”
17. Importance of Core Stability Motor control
Carefully coordinated contractions from antagonistic muscles is necessary to stabilize during posture, activity and to react to perturbations.
Muscle activity assists with attenuating forces transmitted through the lower extremity to the spine during activity
Neuromuscular training reduced serious knee injury in females by 62% (Hewett, 1999)
Included abdominal curls, back extension exercise
18. Importance of Core Stability Muscular capacity( ie: endurance)
Trunk muscle endurance is of greater value than the ability to generate force in the prevention of LBP (McGill, 2003)
19. Importance of Core Stability “…the product of motor control and muscular capacity of the lumbo-pelvic-hip complex.”
Leetun D T, Ireland M L, Willson J D, Ballantyne B T, and Davis I M, Core stability measures as risk factors for lower extremity injury in athletes. Med Sci Sports Exerc, 2004. 36(6): 926-34.
20. Importance of Core Stability What is needed to achieve optimal stability?
Depends on task/ activity
Balance/ symmetry for co-contraction
Endurance/ motor control during fatiguing tasks
Same muscles that stabilize also needed for breathing at times of high O2 demand (fatiguing exercise)
Loss of stabilization during high intensity exercise?
21. “What is: Core Dysfunction”
22. Core Dysfunction Poor/ altered function of muscles that stabilize the lumbar-pelvic-hip complex
Poor muscular endurance
Pain/ injury avoidance
The important question:
What happens during activity when muscles cannot stabilize the lumbar spine, pelvis and hips?
23. Core Dysfunction Lumbar spine experiences compressive loads >6000N
Passive restraints able to resist only 90N
Remaining support provided by active tissue
What happens when muscles fatigue quickly or at different rates?
24. Low Back Pain Core Dysfunction is common in persons with LBP
25. Low Back Pain Non-specific LBP presents a major clinical problem due to the likelihood of high cost, limited activity levels and recurrence.
Back injuries account for 20% of all injuries and illnesses in the workplace
2% of the US workforce are compensated for back injuries each year
Enormous economic burden ?$25 billion annually
26. Low Back Pain The likelihood of experiencing LBP increases with age
peak prevalence of LBP occurs in persons aged 55-64 years in US
85-90% of the population is likely to experience an episode of low back pain in their lifetime
2-5% of the population at least once every year.
LBP causes the greatest level of activity level limitations in persons less than 45 years.
27. Low Back Pain Back pain etiology is multifactorial
What do we know about risk for developing LBP?
Previous LBP including (frequency and duration of symptoms)
Weak, highly fatigable and unbalanced muscles
Specifically, poor lumbar paraspinal endurance
Poor spinal flexibility
Reduced lumbar lordosis
28. Back to the core…
29. The “core” question… How does fatigue affect muscular stability of the lumbar spine, pelvis and hips?
In the presence of Recurrent Low Back Pain?
Poor core stability
How does this affect Lower Extremity muscle function?
Lower extremity injury risk??
30. Research Findings Persons with LBP who fatigue quicker (lumbar extension endurance) tend to have more quadriceps inhibition
Localized lumbar paraspinal muscle fatigue causes increased quadriceps inhibition
Hart, et al, 2005
32. Central Activation Ratio (C.A.R.) CAR = estimate of muscle inhibition
FMVIC ? Force of MU voluntarily recruited
FSIB ? Force of MU electrically recruited
FMVIC + FSIB ? Force of TOTAL MU pool
33. Research Findings Compensation for local lumbar paraspinal fatigue during gait
Similar to avoidance strategy observed in persons with injured/ reconstructed knee -Hart et al 2005
34. Research Findings Postural compensation for local lumbar fatigue
Forward trunk posture (Madigan, 2006)
More anterior COP during stance
Redistribution of ankle, knee and low back torques during stance
How will this affect Gait?
35. Is trunk forward lean bad?
36. Is trunk forward lean bad? Anteriorly displaced ground reaction force vector during activity/ gait
Reduces sagittal plane knee joint moment
Indicates quadriceps eccentric control during gait
38. Trunk Forward Lean Alters force attenuation at the knee
Etiology or forward lean?
Weak Lumbar paraspinals
Poor endurance in muscles that stabilize pelvis, spine, hips?
Higher thoraco-lumbar disc loads
Quadriceps atrophy/ weakness
LE joint surfaces exposed to unusual/ excessive forces
39. Trunk Forward Lean “Flat-back” patients show similar gait adaptations to persons with knee OA
Reduced velocity, reduced stride length, increased stance phase duration
Note continued high force during mid-stance in persons with forward flexed trunk posture during gait
40. Trunk Forward Lean Compensation for forward flexed position of the trunk is a crouched posture
Flexed knee and hip in stance and during gait (also similar to patients with advanced OA)
Places weaker gluteals in a mechanically advantaged position
Higher demand on quadriceps
41. Core Stability and LE Injury Inappropriate positions of hips and trunk during gait or landing may place LE joints at risk for injury
Inability of hip rotators to control femur rotation ? knee valgus/ internal rotation
42. Gait Compensations Persons recurrent LBP exhibit a quadriceps dominant pattern during gait. (Hart, 2005)
Adaptation to poor spine, pelvis, hip muscular stability?
43. Gait Compensations What other group exhibits quadriceps dominance, trunk lean, poor control of femur rotation?
“position of no return”
Body forward flexed
Tibia externally rotated
44. Review Persons with poor Lumbo-pelvic-hip stability
During exercise Fatigue:
Deteriorated postural control
Difficult for hip muscles to appropriately position femur during gait, landings, etc
Trunk Forward Lean
Re-distributing Lower extremity forces during gait
Reduced knee joint torque during gait
Reliance on proximal, postural muscles
(which are probably weak, inhibited, poor endurance)
What absorbs forces if muscles cannot?
45. Discussion… “Core stability may provide several benefits to the musculoskeletal system, from maintaining low back health to preventing knee injury”
46. Thank you for your attention…