Differences of quadriceps activity during inline lunge by using FMS assessment.
Jong-Kyung Lee, Jae-Kwang Lee, Jong-Ha Hwang and 2 others
PMID 33642689WHAT IT FOUND
Healthy adults who performed the inline lunge test well used their inner thigh muscle more than their outer.
Those who performed it poorly used the outer muscle more. This suggests poor form shifts load to the vastus lateralis, potentially requiring targeted inner thigh strengthening.
Key findings
01Participants who scored 3 on the Functional Movement Screen (good form) showed significantly higher muscle activity in the vastus medialis (inner thigh) compared to the vastus lateralis (outer thigh).
02Participants who scored 2 (poor form/compensation) showed significantly higher muscle activity in the vastus lateralis compared to the vastus medialis.
03Both groups showed significant differences in muscle activity patterns between the downward and upward phases of the lunge.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only 32 healthy young adults, limiting generalisability to clinical populations or older adults. The FMS is a screening tool, not a diagnostic assessment; the 'Score 2' group included various types of errors (compensation, loss of balance), so the muscle pattern may not be specific to one type of dysfunction. This was a cross-sectional comparison of muscle activity, not an intervention study, so it does not prove that changing the muscle pattern improves outcomes or prevents injury.
Declared interests
None declared.
The easy way to misread this
Do not assume that vastus lateralis dominance is the cause of the poor score or that correcting it will improve the score. The study shows an association between form quality and muscle recruitment pattern in healthy adults, not a causal mechanism or a validated treatment effect.