BACKGROUND: The degree of quadriceps femoris muscle (QF) atrophy is recognised as one of the key factors of poor knee function and patient's outcome, despite successful reconstruction of anterior cruciate ligament (ACL). AIM: The study assessed whether muscle preconditioning with ischemic exercise can attenuate loss of QF volume, strength, and function after ACL reconstruction. DESIGN: Prospective, single-centre, quasi-randomized, controlled trial with sham intervention. SETTING: University Medical Centre and Laboratory of Physiotherapy Research. POPULATION: Patients with total ACL rupture elected for reconstructive surgery. METHODS: Twenty subjects undergoing ACL reconstruction performed 5 exercise sessions during the last 10 days before surgery. They were assigned into two groups performing either low-load ischemic knee-extension exercise (ischemic group), or standard knee-extension exercise (sham group). QF volume, maximal voluntary isometric contraction torque and single-leg anterior reach distance were assessed prior to preconditioning and at 4 and 12 weeks post-surgery. RESULTS: There were no significant differences between the groups in any of the variables prior to, or after surgery. The deficit in QF vastii volume increased (p < 0.001) to 20 +/- 5% in ischemic and 23 +/- 10% in SHAM group at 4 weeks and persisted (p < 0.001) at 16 +/- 4% in ischemic and 20 +/- 11% in sham group at 12 weeks post-surgery. Deficit in QF maximal isometric torque persisted (p < 0.05) at 15 +/- 15% in ischemic and 22 +/- 16% in sham group at 12 weeks post-surgery. There were no significant differences in single-leg anterior reach distance between the groups at any time point. CONCLUSIONS: Short-term preconditioning with low-load ischemic exercise exhibited no different effect on QF muscle mass, isometric strength, or knee functional loss than comparable standard exercise in patients undergoing ACL reconstruction.

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