Keywords

Anterior cruciate ligament reconstruction; quadriceps strength; neuromuscular function; corticospinal excitability; sex differences; limb symmetry index

Abstract

Anterior cruciate ligament reconstruction (ACLR) is associated with persistent quadriceps dysfunction, including muscular weakness and altered spinal and cortical excitability. While recovery has been widely studied, most investigations focus on isolated domains and fixed postoperative time points. Emerging evidence suggests females often experience slower or less complete quadriceps recovery compared to males, yet the time-dependent nature of these sex-specific outcomes remains unclear. The purpose of this study is to examine whether relationships between time since ACLR and quadriceps neuromuscular outcomes differ by sex across muscular, spinal, and cortical domains. Adults aged 18–35 with a history of primary, unilateral ACLR were enrolled between 6 months to 10 years post-surgery to capture a broad range of functional recovery stages. Peak isokinetic knee extension torque and total work assessed muscular outcomes, the Hoffmann reflex measured spinal excitability, voluntary activation was assessed using the central activation ratio, and active motor threshold derived from transcranial magnetic stimulation was used to index cortical excitability. In males, greater quadriceps strength was associated with longer time since surgery, whereas females showed weaker associations. Females also demonstrated lower uninvolved limb strength and greater limb symmetry indices, suggesting symmetry may reflect bilateral weakness rather than recovery. Measures of voluntary activation and spinal excitability were not associated with time from surgery in either sex. In contrast, corticospinal excitability improved over time in females, as indicated by lower active motor threshold values at longer durations post-surgery. These findings demonstrate that recovery of quadriceps neuromuscular function following ACLR is domain-specific and sex-dependent. Time from surgery alone may not reflect meaningful recovery, particularly in females, highlighting the importance of evaluating both muscular and neural factors when assessing rehabilitation outcomes.

Thesis Completion Year

2026

Thesis Completion Semester

Spring

Thesis Chair

Norte, Grant

College

College of Health Professions and Sciences

Department

Kinesiology and Rehabilitation Sciences

Thesis Discipline

Kinesiology

Language

English

Access Status

Open Access

Length of Campus Access

None

Campus Location

Orlando (Main) Campus

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Rights Statement

In Copyright