Appraising the Validity of Tools to Measure Multijoint Leg Power: A Systematic Review.
Purva Trivedi, Robert Gilbert, Gail Dechman
PMID 33778473WHAT IT FOUND
No existing tool reliably measures maximum multijoint leg power for older adults.
Three devices were reviewed, but all had validation flaws. Correlation does not prove accuracy. Without a valid measure, therapists cannot accurately prescribe or track leg power rehabilitation.
Key findings
01The review found no tool that met inclusion criteria for measuring maximum multijoint leg extension power.
02Validity was assessed using correlations, which fail to show if the absolute power values from the new tool match the reference standard.
03The leg extensor power rig was validated against single-joint or bilateral movements that do not accurately represent multijoint leg extension.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The review only included studies that attempted to validate instruments; it did not assess the reliability or responsiveness of these tools in clinical populations. The authors developed their own critical appraisal criteria because no standardized tool existed for this type of validation study. Some included studies did not clearly describe their methodology, requiring the authors to contact the original investigators for clarification.
Declared interests
The review notes that conflicts of interest were undeclared in all three included studies. The leg extensor power rig study had financial support, while the other two did not declare funding.
The easy way to misread this
Do not assume that a high correlation between two measurement tools means they give the same result. A tool could report double the actual power and still correlate strongly with the reference standard. This review shows that without agreement analysis, these leg power tools cannot be trusted for precise exercise prescription.