The Impact of Core Stability on Lower Extremity Injuries: A Systematic Review of the Literature

1. Tara Cameron Sarah Honkanen Wesley Maunu Nicole Stefanson Sara Zboya Sophia Zhao Marc Roig The Impact of Core Stability on Lower Extremity Injuries: A Systematic Review of the Literature

2. Outline • Introduction • Methods • Results • Discussion • Limitations • Conclusion • Clinical Implications • Recommendations for Future Research

3. Introduction • The word “core” and the idea of training the “core” has become very popular • In spite of its popularity, a universally accepted definition of “core stability”, “core” and the muscles that constitute the “core” has yet to be established

4. Introduction • Core Stability Definition1: • 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.

5. Three Major Systems of Core Stability2,3

6. Previous Research • Number of studies investigating core muscle activation and core stability function either in healthy or injured individuals • Results used as rational for use of core stability training for improving spinal stability and postural control

7. Rationale for Core Stability Training • Cresswell4 • Transverse abdominis (TA) first muscle activated during expected and unexpected loading of the trunk • Anticipatory function • Hodges & Richardson5,6 • Same activation pattern found prior to upper and lower extremity movements

8. Rationale for Core Stability Training • Van Dieen7, Hodges & Richardson8 • Patients with low back pain had altered trunk muscle activation patterns compared to healthy controls • Combination of results suggests: • Anticipatory core muscle activation of TA, required for movement in healthy adults, is altered in injured patients  reduced spinal stability

9. Rationale for Core Stability Training • In addition to providing spinal stability, core stability training may enhance force transmission to the extremities • May play a role in lower extremity injury occurrence

10. Rationale for this Systematic Review • Role of core stability in force transmission to the extremities, and in particular the effect of core stability on extremity injuries and injury prevention has received little attention • Most of the literature on this topic comes from review articles • Citing the same few authors

11. Rationale for this Systematic Review • Willardson 2007: • Core stability training: Applications to sports conditioning programs • Wilson et al. 2005 : • Core stability and its relationship to lower extremity function and injury • Myer et al. 2008: • Trunk and hip control neuromuscular training for the prevention of knee joint injury

12. Rationale for this Systematic Review • To our knowledge no systematic review has been conducted on this topic • The question remains.... Is core stability training effective for reducing lower extremity injuries? Are there more effective methods of training?

13. Purpose To investigate the evidence concerning: • Core stability measures predicting lower extremity musculoskeletal injury risk • The effectiveness of core stability training as a means of lower extremity injury prevention

14. METHODS

15. Search Strategy • Databases • Medline (1950- Present) • EMBASE (1980- Present) • CINAHL (1982- Present) • SportDiscus • PubMed (1949- Present) • Web of Science • Grey Literature • Last Search: January 2009

16. Study Selection • Title Screen • Abstract Screen • Full Text Screen • Using a standardized screening tool to determine consensus • Inclusion and Exclusion Criteria

17. Inclusion Criteria • Measured core stability or provided a core stability training program as a component of the intervention • Examined prevention, occurrence, or recurrence of musculoskeletal lower extremity injuries • Included participants with a minimum mean age of 18 years who were generally healthy, trained or untrained • Were written in English

18. Operational Definition of Core Stability • Ability of the specific core musculature to stabilize the spine and pelvis in order to facilitate force transmission to the extremities • 3 Core Musculature Subsystems: • Inner spinal stabilizers capable of controlling the lumbar segments • Outer spinal stabilizers concerned with controlling trunk movements • Lumbopelvic-extremity muscles which act to maintain lumbopelvic stability on fixed extremities or produce movement of the extremities on a stable trunk and pelvis

19. 3 Core Musculature Subsystems

20. Exclusion Criteria • Were not experimental in design • Examined only the prevention of injuries pertaining to the back • Examined or included interventions that only measured or targeted muscles of subsystem III

21. Quality Assessment • Study Design • Sackett’s Levels of Evidence as described by Oxford Center for Evidence Medicine12 • Methodological Quality • “Checklist for Measuring Quality” by Downs and Black13

22. Data Extraction • Standardized Data Extraction Form • Study Design and Purpose • Operational Definition of Core/Core Stability • Characteristics of Participants • Methods of Measuring Core Stability • Interventions for Core Stabilization • Baseline and Follow-up Outcome Measures • Results and Conclusions • Limitations and Suggestions for Future Studies

23. Data Analysis • Meta-analysis not performed due to: • Study heterogeneity • Participants • Interventions • Outcome Measures • Methods of Measuring Core Stability • Duration of Follow-up • Inability to calculate effect size • Qualitative Analysis • Study Results • Sackett’s Levels of Evidence • Grades of Recommendation

24. RESULTS

25. Search and Selection

27. Study Selection • Main Reasons for Exclusion: • Review article, not experimental in design • Failed to Measure core stability or provide a core stability intervention • Failed to examine injury prevention • Failed to investigate lower extremity injuries • No articles of relevance found with Web of Science or Grey Literature Search

28. Methodological Quality Assessment • Downs and Black Tool • Range = 14-20/28 • Mean = 16/28 • 95.8% agreement between reviewers • External validity category

29. Sackett’s Level of Evidence

30. Study Characteristics • Core Stability as Risk Factor

31. Study Characteristics • Core Stabilization Intervention

32. Qualitative AnalysisCore stability as a Risk Factor • Injured vs. Uninjured athletes • Leetun et al.16: • Injured athletes demonstrated lower core stability measures, especially for hip abduction (P=0.02) and external rotation strength(P=0.01) • Zazulack et al.18: • Injured athletes demonstrated compromised core stability, measured as trunk displacement after sudden force release (P<0.05)

33. Qualitative Analysis Core stability as a Risk Factor • Injured vs. Uninjured athletes • Zazulack et al.17: • Injured female athletes had significantly decreased core stability , measured as error in active proprioceptive repositioning (P≤ 0.05); injured male athletes did not

34. Qualitative Analysis Core stability as a Risk Factor • Lower Extremity Injury Predictors • Leetun et al.14: • Hip external rotation strength was the sole significant predictor of lower extremity injuries in athletes (OR=0.86). • Zazulack et al.17,18 : • Female athletes: a combination of factors related to core stability (trunk displacements, proprioception, history of low back pain) predicted knee injury risk (84% concordant observation, P<0.0001) • Male athletes: history of low back pain was the only significant knee injury risk predictor

35. Qualitative Analysis Core stability as a Risk Factor • Summary • Studies used different operational definitions of core and methods of measuring core stability • Studies provided level 2b evidence suggesting that impaired core stability is a risk factor for lower extremity injuries in athletes

36. Qualitative Analysis Core Stabilization Intervention • Intervention • In all three studies, core stabilization exercises were used in combination with other interventions • Peate et al.15: • Multi-disciplinary program with seminars emphasized functional movement, proper body mechanics, core muscles recruitment, worksite analysis, four physiotherapy ball core strengthening exercises • Cusi et al.19: • Physiotherapy ball for core strengthening in addition to a standard stretching and fitness program performed by the control group

37. Qualitative Analysis Core Stabilization Intervention • Intervention • Sherry et al.16: • Progressive agility and trunk stabilization exercises , and icing • Control group: static stretching and isolated progressive hamstring resistance exercise, and icing

38. Qualitative Analysis Core Stabilization Intervention • Outcome Measures • Injury and re-injury rate were used as outcome measures in all studies • There was an absence of direct and specific measurement of core stability and core strength

39. Qualitative Analysis Core Stabilization Intervention • Results • Peate et al.15: • Significantly decrease total number of injuries (42%) and lost time injuries (62%) for back injuries and upper extremity injuries, but not for lower extremity injuries (P=0.4624, 0.1292 respectively) • Cusi et al.19: • No significant difference in lower back and groin injury rate between intervention group and control group (P value was not reported by the study)

40. Qualitative Analysis Core Stabilization Intervention • Results • Sherry et al.16: • Intervention was superior to the control in preventing hamstring strain re-injury in athletes (2 weeks post-return to sports P=0.00343, 1 year post-return to sports P=0.0059) • No direct measurements for trunk stabilization was performed • Not possible to conclude that results were due to improvements in core stability

41. Qualitative Analysis Core Stabilization Intervention • Summary • Overall, studies used different operational definitions of core, different core stabilization interventions and different or absent direct and specific measurement of core stability and core strength • The studies provided inconclusive level 1b and 2b evidence suggesting the effectiveness of core stabilization interventions in decreasing lower extremity injury or re-injury rate

42. Discussion • Few quality studies examining the relationship between core stability and lower extremity injuries were found • Inconsistent evidence in support of core stability as a risk factor for predicting lower extremity injuries • Inconclusive evidence to support core stability training in prevention of lower extremity injuries

43. Misrepresentation of Current Evidence • Review articles are written based highly on theory due to lack of scientific evidence • When research is added to theory misrepresentation can occur

44. Misrepresentation of Current Evidence • Example • “Research from the rehabilitation literature has demonstrated the effectiveness of core stability exercises for reducing the likelihood of lower back and lower extremity injuries”9 • Studies referenced either did not have outcome measures of core strength or stability, or used multiple interventions at once22

45. Misrepresentation of Current Evidence • Muscles Which Constitute the “Core” • Leetun16 was referenced in the following statement “A recent prospective study suggests that deficiencies in core muscle capacity may increase the risk of lower extremity injury”10 • The muscles referred to by Leetun14 are the hip external rotators which can be a component of the “core” but alone are not considered the “core”

46. Theoretical Support • Three Subsystems3 • Neural subsystem controls the active lumbopelvic musculature • Alters compressive forces between the passive bony components of the lumbopelvic region • Manages stability

47. Theoretical Support • Kinetic Chain Theory • Human movement occurs through a sequencing of body segments from proximal to distal1 • Proximal base of support necessary for successful distribution of forces20,1 • Core muscle activation often preceded lower extremity muscle activity during movement5,6 • Deficits in core stability may alter loads tolerable by distal segments and place them at higher risk for injury20, 1

48. Limitations of the Review • No single universal definition of “core” or “core stability” • Limited number of studies available on topic • Meta-analysis not possible • Only included articles written in English

49. Clinical Implications • Major influence towards developing a standardized and universal definition of “core” and “core stability” • More comparable scientific studies to be conducted • Promote standardized, valid and reliable methods of assessing core stability • Facilitate interventions with specific parameters • Allow objective and functional outcomes to be measured

50. Recommendations for Future Research • Well Controlled, Longitudinal RCT • Examine the effectiveness of a core stability intervention in the prevention of lower extremity injuries • Measure Core Stability • Pre- and post- intervention to ensure the results can be attributed to a difference in core stability • Have a comprehensive definition of core stability