Isokinetic Quadriceps and Hamstring Peak Torque in Athletes Aged 10-50+: Preoperative Uninvolved Limb Reference Values for ACL Reconstruction.

International journal of sports physical therapy · 2026 · Cohort · PT
John D Kipp, Amy L Bednarek, Marc A Sherry, Michael W Keefe, Elizabeth S Chumanov

In 321 athletes scheduled for ACL surgery, quadriceps and hamstring strength (adjusted for body weight) declined with age, but the hamstring-to-quadriceps ratio stayed stable. The widely used 3.0 Nm/kg strength target may not fit patients outside their 20s.

Key findings

1

Quadriceps and hamstring peak torque (normalised to body mass) both declined significantly with age, explaining roughly a quarter of the variation in each muscle group. The decline was gradual and similar in shape for men and women.

2

Males trended toward higher normalised peak torque than females, but the difference did not reach statistical significance for either the quadriceps or the hamstrings.

3

The hamstring-to-quadriceps ratio was essentially flat across the age range and was not predicted by age, sex, or their interaction. The cohort's average ratio fell below the 60% threshold commonly recommended after ACL surgery.

MethodologyResultsClinical Relevance

Single-blind randomized controlled trial. Sixty-four participants were randomized across two intervention arms and assessed at twelve weeks for the primary outcome…

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