Establishing Normative Values for Inter-Limb Kinetic Symmetry During Landing in Uninjured Adolescent Athletes.
Adam W VanZile, David M Reineke, Matthew J Snyder and 3 others
PMID 34386285WHAT IT FOUND
Uninjured adolescent athletes typically show 16-20% asymmetry in landing forces.
In a small group of post-ACL reconstruction athletes, six of eleven exceeded the 75th percentile of this norm, consistently loading their healthy limb more than the surgical one.
Key findings
01Uninjured athletes averaged 16.4% asymmetry during drop vertical jumps and 20.2% during countermovement jumps.
02Six of the eleven post-ACL reconstruction athletes showed asymmetry above the 75th percentile of uninjured norms.
03All six atypical post-ACL reconstruction athletes loaded their uninvolved limb more heavily than the reconstructed limb.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The post-ACL reconstruction group was very small (n=11), so these findings are an example rather than a validated screening tool. The study did not link these asymmetry levels to actual re-injury rates, so it is unknown if correcting the asymmetry improves outcomes. Most clinics do not currently have the portable force plate technology required to collect this data. Only peak vertical ground reaction forces were measured; joint-specific loading patterns were not assessed.
Declared interests
No specific funding sources or conflicts of interest are declared in the provided text.
The easy way to misread this
Do not interpret the 75th percentile threshold as a validated return-to-sport criterion. The authors state that no well-established thresholds exist for safety, and this study only describes where a small group of athletes fell relative to uninjured peers without proving that exceeding this value predicts re-injury.