Impact of quadriceps strengthening on response to fatiguing exercise following ACL reconstruction

Christopher Kuenze, Moataz Eltoukhy, Adam Kelly, Chang Young Kim

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


Objectives Patients commonly experience altered response to fatiguing exercise after ACL reconstruction (ACLR). The objective of this study was to assess the impact of quadriceps strengthening on response to exercise after ACLR. Design Clinical trial. Methods Ten participants with a history of primary, unilateral ACLR (sex = 9F/1M, age = 21.0 ± 2.8 years, BMI = 23.7 ± 2.7 kg/m2) and 10 healthy participants (sex = 9F/1M, age = 22.2 ± 3.2 years, BMI = 23.8 ± 3.9 kg/m2) participated. ACLR participants completed a 2-week quadriceps strengthening intervention including 14 progressive strengthening exercise sessions. Normalized knee extension maximum voluntary isometric contraction (MVIC) torque (Nm/kg) and quadriceps central activation ratio (%, CAR) were measured before and after a 30-minute fatiguing exercise protocol. ACLR participants completed testing before and after the 2-week intervention while control participants completed a single testing session. Results The intervention significantly improved normalized knee extension MVIC torque (pre-intervention = 1.85 ± 0.67Nm/kg, post-intervention = 2.09 ± 0.81Nm/kg, p = 0.04) and quadriceps CAR in the ACLR involved limb (pre-intervention = 86.51 ± 5.03%, post-intervention = 92.94 ± 5.99%, p = 0.02). Quadriceps CAR (pre-intervention = 1.13 ± 9.04%, post-intervention = −3.97 ± 4.59%, p = 0.16) and normalized knee extension MVIC torque (pre-intervention = 0.26 ± 20.90%, post-intervention = −8.02 ± 12.82%, p = 0.30) response to exercise did not significantly change from pre-intervention to post-intervention conditions. Conclusions Two weeks of quadriceps strengthening reduced this between group difference in the involved limb which may indicate restoration of more optimal quadriceps neuromuscular function and increased demand on the quadriceps during physical activity.

Original languageEnglish (US)
Pages (from-to)6-11
Number of pages6
JournalJournal of Science and Medicine in Sport
Issue number1
StatePublished - Jan 1 2017


  • Disinhibitory modalities
  • Knee injuries
  • Muscle fatigue
  • Quadriceps muscle
  • Torque

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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