This EMG study quantifies how knee flexor and extensor muscles coactivate during maximal isokinetic contractions. It asks whether antagonist coactivation patterns differ between nonathletic normals, quad-dominant athletes without hamstring training, and athletes who regularly train both muscle groups. The study's central question: does muscular imbalance alter the hamstring's protective contribution to knee stability?
The reflex assumption in athletic training has long been that stronger muscles equal safer joints. Baratta's data breaks that assumption: a quad-dominant athlete can have superior hamstring strength as an agonist while simultaneously having suppressed hamstring coactivation as an antagonist — and it is the coactivation, not peak torque, that protects the ACL.
When you see a high-level jumping athlete (volleyball, basketball, track) with an ACL injury or recurrent instability, prescribe hamstring-dominant rehabilitation as the primary modality, not just quadriceps reconditioning. The neural inhibition that depresses coactivation is reversible: significant recovery appears within one week of targeted hamstring curls, and full normalization within two to three weeks.
This paper is the foundational evidence behind hamstring-first protocols in ACL reconstruction rehab and conservative ACL management. The hamstrings do not just generate posterior tibial force as agonists; they continuously redistribute articular contact pressure and share ligament load during every loaded extension movement.
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This EMG study quantifies how knee flexor and extensor muscles coactivate during maximal isokinetic contractions. It asks whether antagonist coactivation patterns differ between nonathletic normals, quad-dominant athletes without hamstring training, and athletes who regularly train both muscle groups. The study's central question: does muscular imbalance alter the hamstring's protective contribution to knee stability?
The reflex assumption in athletic training has long been that stronger muscles equal safer joints. Baratta's data breaks that assumption: a quad-dominant athlete can have superior hamstring strength as an agonist while simultaneously having suppressed hamstring coactivation as an antagonist — and it is the coactivation, not peak torque, that protects the ACL.
When you see a high-level jumping athlete (volleyball, basketball, track) with an ACL injury or recurrent instability, prescribe hamstring-dominant rehabilitation as the primary modality, not just quadriceps reconditioning. The neural inhibition that depresses coactivation is reversible: significant recovery appears within one week of targeted hamstring curls, and full normalization within two to three weeks.
This paper is the foundational evidence behind hamstring-first protocols in ACL reconstruction rehab and conservative ACL management. The hamstrings do not just generate posterior tibial force as agonists; they continuously redistribute articular contact pressure and share ligament load during every loaded extension movement.