Strength Training Effects on Muscular Regeneration after ACL Reconstruction

ABSTRACTPurposeProtracted quadriceps muscle atrophy is observed after anterior cruciate ligament reconstruction (ACL-R). The aim of this study was to assess if quadriceps strength training with eccentric overload (CON/ECC+) is more efficient to induce muscle regeneration after ACL-R than conventional concentric/eccentric (CON/ECC) strength training.MethodsBiopsies from the vastus lateralis muscle were obtained from 37 recreational athletes after 12 weeks of regular rehabilitation following ACL-R and again after 12 weeks with twice a week either conventional CON/ECC (n = 16) or CON/ECC+ (n = 21) one-legged supervised leg-press training. Immunohistochemical analyses were used to determine satellite cell number (SC, Pax7+), activated SCs (Pax7+/MyoD+), fibers expressing myosin heavy chain (MHC) I, II and neonatal, fiber cross sectional area (FCSA). Magnetic resonance imaging was performed to measure quadriceps cross sectional area (MCSA) and isokinetic testing for the measurement of quadriceps strength.ResultsCON/ECC+ induced a significantly (p = 0.002) greater increase in MCSA than CON/ECC. There also was a significant increase in the FCSAs of all fiber types and in quadriceps strength, however, without significant difference between training groups. Only CON/ECC+ training lead to a significant (p

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