Influence of Antagonistic Hamstring Coactivation on Measurement of Quadriceps Strength in Older Adults.
Jason-Flor Sisante, Na Wang, David T Felson and 4 others
PMID 31585496WHAT IT FOUND
Higher hamstring coactivation was linked to lower measured quadriceps strength in older adults with or at risk for knee osteoarthritis.
It was seen mainly in women. A low strength-test score may not mean true quadriceps weakness.
Key findings
01For every 1% increase in median combined hamstring coactivation, measured quadriceps strength was 0.141 Nm lower across all participants. The same pattern was found in women but not men.
02Women had greater combined, medial, and lateral hamstring coactivation than men.
03The third quartile of medial hamstring coactivation, compared with the first quartile that had 0% coactivation, had lower quadriceps strength in all participants, women, and men.
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How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was a cross-sectional association, so it cannot show that hamstring coactivation caused lower measured quadriceps strength. The paper states that 28% of participants had uninterpretable surface electromyography data, so coactivation results do not include all participants who completed the visit. Quadriceps strength was measured during seated isokinetic knee extension, not during walking, transfers, or other daily tasks. The test relied on maximal effort, and pain, unfamiliarity, or fatigue could have reduced some participants' effort. The sample was community-dwelling adults with or at risk for knee osteoarthritis, and all were independently ambulatory, so results may not apply to more severe or non-ambulatory knee problems. Subcutaneous fat was not measured, and women had more thigh fat than men, which could have affected surface electromyography readings.
Declared interests
The supplied publication types list NIH extramural research support. No conflict-of-interest statement appears in the supplied text.
The easy way to misread this
Do not conclude that hamstring coactivation causes quadriceps weakness or that it should be reduced in every patient. This study was cross-sectional, and it found an association between higher coactivation and lower measured torque, mainly in women. It did not test whether lowering coactivation improves strength, pain, or function.