Effects of exercise on lower extremity muscle function after anterior cruciate ligament reconstruction

Christopher Kuenze, Jay Hertel, Joseph M. Hart

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Purpose: Persistent quadriceps weakness due to arthrogenic muscle inhibition (AMI) has been reported after anterior cruciate ligament (ACL) reconstruction. Fatiguing exercise has been shown to alter lower extremity muscle function and gait mechanics, which may be related to injury risk. The effects of exercise on lower extremity function in the presence of AMI are not currently understood. The purpose of this study was to compare the effect of 30 min of exercise on quadriceps muscle function and soleus motoneuron-pool excitability in ACL-reconstructed participants and healthy controls. Methods: Twenty-six (13 women, 13 men) healthy and 26 (13 women, 13 men) ACL-reconstructed recreationally active volunteers were recruited for a case-control laboratory study. All participants completed 30 min of continuous exercise including alternating cycles of inclined-treadmill walking and bouts of squats and step-ups. Knee-extension torque, quadriceps central activation ratio (CAR), soleus H:M ratio, and soleus V:M ratio were measured before and after 30 min of exercise. Results: There was a significant group × time interaction for knee-extension torque (P =.002), quadriceps CAR (P =.03), and soleus V:M ratio (P =.03). The effect of exercise was smaller for the ACL-R group than for matched controls for knee-extension torque (ACL-R: %Δ = -4.2 [-8.7, 0.3]; healthy: %Δ = -14.2 [-18.2, -10.2]), quadriceps CAR (ACL-R: %Δ = -5.1 [-8.0, -2.1]; healthy: %Δ = -10.0 [-13.3, -6.7]), and soleus V:M ratio (ACL-R: %Δ = 37.6 [2.1, 73.0]; healthy: %Δ = -24.9 [-38.6, -11.3]). Conclusion: Declines in quadriceps and soleus volitional muscle function were of lower magnitude in ACL-R subjects than in healthy matched controls. This response suggests an adaptation experienced by patients with quadriceps AMI that may act to maintain lower extremity function during prolonged exercise.

Original languageEnglish (US)
Pages (from-to)33-40
Number of pages8
JournalJournal of sport rehabilitation
Volume22
Issue number1
DOIs
StatePublished - Feb 2013

Keywords

  • Central activation ratio
  • Fatigue
  • Hoffmann reflex
  • Knee injury

ASJC Scopus subject areas

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

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