On completion of the appropriate checklists (see Appendix B for examples) evidence tables were compiled. Table 3 depicts the ratio of appropriate intervention studies found for each key question. Other material such as non-analytical studies and expert opinions were not included in the table. Evidence tables were created for each question in accordance to SIGN 50 guidelines (see Tables 14-19 in Appendices C-H). These tables provided a clear, consistent format to compare and consider the outcomes of each study within the context of the key question. Table 4 demonstrates the spread of evidence level ratings for individual studies compared with key research questions. On further analysis of the SIGN 50 (2004) criteria for grades of recommendation (see Table 5) clinical guidelines were formulated for core stability (see Table 6). These guidelines and their associated gradings were directly linked to the quality of evidence found in response to the key research questions.
Table 3. Key questions versus number of intervention studies allocated.
| Number | Key Question | Intervention Studies |
| 1 | What anatomical, biomechanical and physiological evidence exists that supports the concept of core stability? | 35 |
| 2 | Is there any valid objective measure for core stability? Can any components of core stability be measured to provide a useful clinical measure? | 13 |
| 3 | Does evidence suggest that core stability can influence human performance? | 2 |
| 4 | Is there any correlation between core stability and peripheral injury rates? | 3 |
| 5 | Does core stability training decrease the recurrence or extent of lumbo-pelvic dysfunction? | 16 (including 3 systematic reviews) |
| 6 | Is there any evidence to support specific exercise programmes to enhance core stability? | 17 |
Table 4. Distribution of evidence level ratings from intervention studies compared with Key Questions.
Levels of Evidence
| Key Question | 1++ | 1+ | 1- | 2++ | 2+ | 2- | 3 | 4* |
| 1 | 0 | 1 | 0 | 0 | 5 | 4 | 25 | 5 |
| 2 | 0 | 0 | 0 | 0 | 2 | 3 | 8 | 2 |
| 3 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 8 |
| 4 | 0 | 0 | 0 | 0 | 2 | 1 | 0 | 7 |
| 5 | 0 | 4 | 2 | 0 | 3 | 5 | 2 | 3 |
| 6 | 0 | 3 | 0 | 0 | 2 | 1 | 11 | 7 |
* Studies rated as Evidence Level 4 were not intervention studies. Studies that were based on expert opinion and had no analytical basis were graded an evidence level rating of 4. Intervention studies were graded 3 and above depending on study design and methodology. This study was primarily interested in intervention studies.
Table 5. Description of grades of recommendation for guidelines
| Grades of recommendation | |
| A | At least one meta analysis, systematic review, or RCT rated as 1++, and directly applicable to the target population; or A systematic review of RCTs or a body of evidence consisting principally of studies rated as 1+, directly applicable to the target population, and demonstrating overall consistency of results |
| B | A body of evidence including studies rated as 2++, directly applicable to the target population, and demonstrating overall consistency of results; or Extrapolated evidence from studies rated as 1++ or 1+ |
| C | A body of evidence including studies rated as 2+, directly applicable to the target population and demonstrating overall consistency of results; or Extrapolated evidence from studies rated as 2++ |
| D | Evidence level 3 or 4; or Extrapolated evidence from studies rated as 2+ |
Adapted with permission from SIGN 50 Guideline Developers Handbook (2004)
Table 6. Guideline Recommendations for core stability
| Key Question | Grade | Recommendation |
| 1 | C | Anatomical, biomechanical and physiological evidence exists that supports the concept of core stability. |
| 2 | C | Objective measures for measuring core stability are available and should be used to assist intra and inter tester reliability. |
| 3 | D | Core stability has a direct influence on human performance. |
| 4 | D | Core stability training should be part of any injury prevention programme. |
| 5 | B | Core stability training can decrease the recurrence of lumbo-pelvic dysfunction. |
| 6 | C | Core stability can be improved with specific exercises. |
Chapters V-X discuss the background evidence behind the clinical guideline recommendations for core stability. It is important not to view guideline statements with lower grades as being less important (Harbour and Miller, 2001). The guideline created from key question 1 is arguably the most important for the core stability concept and it primarily has a C grading due to the types of studies performed in anatomy, biomechanics and physiology. This guideline is more of a foundation statement for the concept of core stability as it does not directly have a clinical basis. The guidelines created from key questions 3 and 4 have received D gradings because very few intervention studies were identified and the majority of evidence was based on expert opinion.